U.S.A., Arkansas, “Sevier Co., Ark. Saline R. about 18 miles east of DeQueen.”

None–see comments below in Discussion.

Male: unknown.

Female: Length 10 mm, elytral apices regularly oval, serration absent, lateral margins weakly sinuate, profemora of female with apicoventral tooth present running 1/5 its length.

Known only from the type locality.

Unknown

Dineutus amazonicus was described from a single female specimen collected in Arkansas during the 1930’s. The species, as described by Hatch (1930), is unique among all other North American Dineutus in having females with an sub-apicoventral tooth present on the profemora, running approximately 1/5 its length. In Dineutus this is a commonly sexually dimorphic character, with the tooth present only in males. Hatch (1930) indicated the elytra of this species are similar to those of D. emarginatus, being regularly rounded and lacking serration.

We were unable to locate the type specimen either at the Smithsonian (F. Shockley, pers. comm.) or Oregon State University (C. Marshall, pers. comm.) where Hatch’s collection was deposited. No specimens in the University of Arkansas collection were identified as D. amazonicus (J. Barnes, pers. comm.). It appears that the type may be missing, and that no other published records of this species have occurred since its description in 1930. Although Hatch’s (1930) description at first sounds dubious, as the profemoral sub-apicoventral tooth is in all other species unique to males, Hatch was unlikely to mistake a female gyrinid for a male (Hatch 1925b, 1926), and it therefore seems unlikely that he described a merely aberrant form. For this reason we have included the enigmatic D. amazonicus, without having seen neither type nor any other specimens of this species.

The first author recently visited the type locality in an attempt to recollect this species, but was unsuccessful. The locality, Saline River, a large mud bottom river, also had present D. ciliatus as described by Hatch (1930), but unsettlingly, the only other species collected at this locality was D. emarginatus, the species stated to be most similar to that of D. amazonicus. Hopefully in the future the type may be rediscovered or this enigmatic species recollected and its relationship with D. emarginatus clarified.

“America”.

8

Gyrinus americanus Linnaeus, 1767: syntype (1 ♀ card mounted) “2 [white label typed black ink]// americanus [beige lable, handwritten in black ink]//” examined online through the Linnaen Society of London’s Linnean’s Insect Collection.

Dineutus metallicus Aubé, 1838: lectotype, here designated (1 ♀ pinned) “MUSEUM PARIS/ CUBA/ M. De LA SAGRA 764-36 [beige label with thin black border, typed black ink]// green circle [underneath is 764/ 36 handwritten in black ink]// metallicus au [beige label, handwritten in black ink, handwriting appears to be Aubé’s, author is partially cut off]// PARATYPE [red label, typed black ink]// LECTOTYPE [red label, typed black ink]//” deposited in the MNHN. Paralectotype (1 ♀ pinned missing right mesothoracic leg past the femur and entire right metathoracic leg) same data as previous except without Aubé’s handwriting label and with “PARALECTOTYPE [red label, typed black ink]//” deposited in the MNHN.

BAHAMAS:Great Exuma: Simons Pt., “23.31.50 75.37.30”, 26.i.1980, leg. S.A. Teale (1 ex. KSEM); Mayaguana Island: 3.viii.1963, leg. C.M. Murvosh, BLT (1 ex. FSCA). CUBA: Holguín river near Biological Station of PN La Mensura, Piloto, 657 m, 11.v.2013, 20.48640N, 75.779134W, leg. A. Deler-Hernández (1 ex. NMPC). DOMINCAN REPUBLIC:La Altagracia: Nisibón, 3.v.1978, leg. R.E. Woodruff & G.B. Fairchild, (1 ex. FSCA); Monte Cristi: 5 km N Villa Elisa, 10–18.v.1985, leg. E. Giesbert (1 ex. FSCA). PUERTO RICO: Almirante Rd., “K.B.Y.”, 9.iii.1935, leg. J.G. Needham (1 ex. MSBA). U.S.A.:The Virgin Islands: St. Thomas, 27.ii.1925, WIBF 011217 (1 ex. WIBF).

Male (Fig. 4C–D): Size: 8.7–9.3 mm. Body form elongate oval; elytral apices with sutural angle produced to a point, with serrations and irregularities present apically, elytra with reticulation very strong laterally, medial disc with reticulation sparse or absent, striae often not apparent, lateral marginal depression of elytra not present; profemora with small sub-apicoventral tooth; protibiae club-shaped with apicolateral margin obliquely angled; mesotarsal claws (Fig. 5C) with ventral margin weakly rounded; venter darkly colored, reddish brown to black, weakly metallic, mesothoracic and metathoracic legs usually lighter in coloration, as well as apex of abdomen; Aedeagus (Fig. 5A, B, D) median lobe in dorsal view shorter than parameres, nearly parallel sided, narrowed in apical 1/6; parameres weakly expanded laterally in apical 1/3, medially weakly curved, flatly rounded apically.

Female (Fig. 4A–B): Size: 8.9–9.1 mm. Body form elongate oval; elytral apices with sutural angle produced, with serrations and irregularities present apically, apicolateral sinuation present, elytra with reticulation strongly present laterally, medial disc with reticulation sparse or absent, striae often not present, lateral marginal depression of elytra absent; profemora without sub-apicoventral tooth; protibiae club-shaped with apicolateral angle rounded; venter darkly colored, reddish brown to black, weakly metallic, mesothoracic and metathoracic legs and apex of abdomen usually lighter in coloration.

Figure 4. 

Dineutus americanus. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus D ♂ ventral habitus. All scale bars ≈ 2 mm.

Figure 5. 

Dineutus americanus. A aedeagus dorsal view B aedeagus ventral view C ♂ mesotarsal claws D aedeagus lateral view. Scale bar for C ≈ 0.10 mm all others ≈ 1 mm.

Dineutus americanus is unique among all other species of Dineutus in North American in having an elongate oval body form (Fig. 4A, C), elytra without a well defined marginal depression, strong lateral reticulation, with striae mostly absent, the elytral apices with the sutural angle produced to a point with apical serrations and irregularities present, in the male having the profemora with a small sub-apicoventral tooth, protibiae that are club-shaped, and in the form of the male aedeagus (Fig. 5A). This species is also unique in being small in size and endemic to the Caribbean, reaching the Florida Keys (Fig. 55A). The species most similar to D. americanus is D. carolinus.

Both sexes of D. americanus can be distinguished from D. carolinus in having the sutural angle of the elytra produced to a point and being generally smaller in size. However, this production can sometimes be highly reduced to only a small point at the sutural angle, especially in males. Both sexes of D. americanus can further be separated from D. carolinus in lacking the marginal depression of the elytra seen in D. carolinus. The absence of the elytral marginal depression is most evident in the humeral region of the elytra, where in D. carolinus it is steep and narrow, becoming larger and shallower posteriad. Dineutus americanus has the elytra more evenly convex with the lateral portions of the disc with a very strongly impressed reticulation, producing a bronzy green appearance. The elytra also often do not have the striae very apparent due to the strong reticulation, whereas the striae are often faint but evident in D. carolinus.

The aedeagus (Fig. 5A) will unambiguously distinguish males of D. americanus from D. carolinus. In D. americanus the median lobe (Fig. 5A) is weakly constricted medially, and only narrowed in the apical 1/6 of its length, whereas that of D. carolinus (Fig. 11A) is parallel sided for much of its length, fairly evenly narrowed in the apical 1/3, and is much more narrow overall. The parameres also differ, with those of D. americanus more curved along both lateral and medial margins.

Females of D. americanus can be distinguished from D. carolinus by several of the above described differences, but also the elytra are much more noticeably lacking the marginal depression.

Whereas other small, elongate-oval species may be confused with D. americanus (e.g. D. emarginatus, D. solitarius and possibly D. assimilis, since the elytral apices are similar) it should again be noted that D. americanus is a Caribbean endemic and its range should limit confusion with all other species except for D. carolinus which is also found in the Bahamas (Fig. 53C).

(Fig. 55A). From the Big Pine Key (Florida Keys, U.S.A.) (Wood 1962), through the Caribbean from the Bahamas to Cuba (Blackwelder 1944; Leng and Mutchler 1914a; Peck et al. 1998), Isle de Pinos (Blackwelder 1944), Jamaica (Blackwelder 1994; Leng and Mutchler 1914b), Dominican Republic (Blackwelder 1944), Puerto Rico, St. Thomas, St. John (Blackwelder 1944), Antigua (Blackwelder 1944; Leng and Mutchler 1914a), to Guadeloupe (Blackwelder 1944; Leng and Mutchler 1914a; b; Peck 2011).

Lentic species (M. Fikáček pers. com.), also an accidental inhabitant of caves in Cuba (Peck et al. 1998).

Many specimens have been misidentified as D. americanus due to a long persisting synonymy issue (see the discussion under D. assimilis). Mistaken records of D. americanus include Ciegler et al. (2003) and Zuellig et al. (2002) for Wyoming and, most likely, the key to larvae provided by Hatch (1927). The true D. americanus is only found in the Caribbean and the Florida Keys (Fig. 55A).

Aubé (1838) does not give any exact label data, nor does he mention whose collection the types came from. The syntype series was identified by the presence of a disc on the specimen, which was checked with the registrar present at the MNHN to ensure dates were prior to the description by Aubé. The other specimens present either did not provide dates or had dates after Aubé’s (1838) publication. The lectotype (Fig. 51D) here designated was selected as it had a label present with Aubé’s handwriting and identification as “metallicus”. We here also confirm that D. metallicus is a synonym of D. americanus as proposed by Schaum (1848).

U.S.A., Florida

15

Dineutus angustus LeConte, 1878: syntype (1♀ pinned) “Type/ 6095 [red label, type in typed black ink, 6095 handwritten in black ink]// Fla. [beige label, typed black ink]// D. angustus/ Lec. [beige label, handwritten in black ink, handwriting appears to be LeConte’s]//” deposited in the MCZ.

U.S.A.:Florida: Alachua Co., 3.ii.1949, leg. B.W. Cooper (2 ex. FSCA); Columbia Co., O’Leno State Park, 12.ii.1966, leg. F.W. Mead (7 ex. FSCA); Florida: Hillsborough Co., “USF Riverfront”, 21.v.1975, leg. G. Cowden (1 ex. FSCA); Suwannee Co., Branford, 16.vii.1934, leg. J.D. Beamer (4 ex. KSEM).

Male (Fig. 6C–D): Size: 9.4–10.8 mm. Body form very narrowly oval, laterally nearly parallel sided; elytral apices rounded with sutural angle produced into a point, rarely with point reduced and elytra appearing completely rounded, elytral apices without serrations and/or irregularities, elytral striae very faint, most evident medially, elytra laterally with strong reticulation, giving a bronzy appearance, medially replaced by fine microreticulation and fine weakly impressed punctures; profemora with small weakly produced sub-apicoventral tooth; protibia weakly club-shaped; venter lightly colored red to reddish orange; Aedeagus (Fig. 7A, B, D) with median lobe in dorsal view parallel sided basally, weakly constricted medially, apically briefly expanded then narrowed in apical 1/4, apex obtusely rounded, in lateral view median lobe narrowed in apical 1/4, in ventral view sperm-groove parallel sided for near entirety of length, apex broadly rounded, parameres very narrow, shortly constricted in basal 1/5, weakly arced in apical half, apically flatly rounded.

Female (Fig. 6A–B): Size: 9.8–10.2 mm. Body form very narrowly oval, laterally nearly parallel sided; elytral apices roundly angled towards sutural production, with sutural angle produced into a point, apical lateral sinuation often absent, to very weakly developed, elytral apices without serrations and/or irregularities, elytral striae very faint, most evident medially, elytra laterally with strong reticulation, giving a bronzy appearance, medially replaced by fine microreticulation and fine weakly impressed punctures; profemora without sub-apicoventral tooth; protibiae laterally weakly curved, apicolateral margin weakly expanded; venter lightly colored, red to reddish orange.

Figure 6. 

Dineutus angustus. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus D ♂ ventral habitus. All scale bars ≈ 2 mm.

Figure 7. 

Dineutus angustus. A aedeagus dorsal view B aedeagus ventral view C ♂ mesotarsal claws D aedeagus lateral view. Scale bar for C ≈ 0.10 mm all others ≈ 1 mm.

Dineutus angustus is unique among all other North American Dineutus in its small size, parallel sided, very narrowly elongate oval body form (Fig. 6A, C), light-colored venter, and somewhat in the shape of the aedeagus (Fig. 7A). This species is most similar to D. discolor and it has been debated whether the two are actually distinct species (Régimbart 1892). Dineutus angustus of both sexes can be distinguished from D. discolor by smaller size, as well as the more parallel-sided and dorsoventrally convex body form. However, the aedeagus of the two species are very similar, with some minor differences. Both aedeagi have the median lobe parallel-sided and very narrow parameres. However, in D. angustus the median lobe has a weak constriction medially subtending a slight expansion apically, and a narrowed apical 1/4, whereas the median lobe in D. discolor is nearly parallel-sided for most of the length, with only a very weak constriction medially. The parameres of D. angustus are more curved in the apical 1/3, and accompanied by a weak constriction in the basal 1/5, in comparison to D. discolor which have the parameres much more parallel-sided.

The shape of the apices of the female elytra of D. angustus differs from those of D. discolor. In D. angustus females the apices are broadly angled towards the sutural production and usually lack an apicolateral sinuation. When it is present (rarely), it is only weakly developed. In D. discolor females the elytra are regularly rounded to the sutural production, with an apicolateral sinuation present.

(Fig. 52D). U.S.A., Southern Georgia, and Eastern Alabama to northern Florida (Roberts 1895; Wood 1962; Régimbart 1907).

Lotic species, seemingly restricted to highly calcareous streams with a basic pH (Young 1954). For more on habitat preference see discussion.

Régimbart (1882) originally considered D. angustus to be a synonym of D. discolor, eventually elevating it to a variation (Régimbart 1892) of D. discolor (comparable now to a subspecies), then eventually accepting it as a species distinct from D. discolor (Régimbart 1902). We have decided to treat D. angustus as a distinct species due to the differences in morphology listed above. The size of the two species in specimens examined for this study only overlap in the extremes, in that the largest specimens of D. angustus only just approach the very smallest of D. discolor. Dineutus angustus was much smaller than any average sized specimen of D. discolor, with only a few female specimens of D. discolor approaching the size of large D. angustus males. Although the aedeagi of both species, which is primarily used here as a delimiter of species boundaries, are very similar, there were some notable differences, even if minor.

Young (1954) noticed that D. angustus in Florida appears to be restricted to calcareous streams with a basic pH, while D. discolor appears to inhabit streams with a more acidic pH. Young (1954) mentions “intergrade” forms occuring from streams of intermediate pH with both typical forms of D. discolor and D. angustus present. However, the evidence for the intergrade was in the number of setigerous punctures, which are known to vary among populations, especially with size. Nevertheless, this led Young (1954) to suggest that D. angustus may represent the basic stream ecotype of D. discolor.

Dineutus angustus appears to be very restricted in range so far found only in northern Florida, southeastern Alabama, and southern Georgia (Fig. 52D), records from Virginia are mentioned by Roberts (1895). Similar to Young (1954), we have only seen D. angustus from northern Florida, and doubt the other records. Given the extensive range of D. discolor and close similarity of that species, we believe it is likely that the two species have been misidentified. Dineutus angustus is rarely collected, and not well represented in collections.

“Lat. 54°”.

273

Not examined. Having examined the type for D. americanus, the most confused name with D. assimilis, it seems that the identity of D. assimilis is secure, so no attempt to loan the type was made.

CANADA:Ontario: Kent Co., Tilbury, vi.1960, leg. K. Stephan (1 ex. FSCA). U.S.A.:Alabama: Perry Co., Boguechitto Creek,19.vi.1962, leg. F.N. Young, #2047 (1 ex. FSCA); Monroe Co., 10km W Bowles, 31°33.094’N, 86°59.956'W, 11.v.2006, leg. K.B. Miller, KBM1105063 (1 ex. MSBA); Arkansas: Benton Co., State Fish Hatchery, 12.iv.1974 (1 ex. FSCA); Conway Co., I-40 Rest Area, 181, 9mi W of State Line, 11.v.1983, leg. L.R. Davis Jr., (1 ex. FSCA); Florida: Alachua Co., Gainesville, 17.vi.1947 (1 ex. FSCA); 2 mi NW Gainesville, 20.iv.1974, leg. J.B. Heppner, blacklight (1 ex. FSCA); pond nr. River Styx, 1.viii.1975, leg. J.B. Heppner (1 ex. FSCA); Newman’s Lake, 25.vii.1975, leg. J.B. Heppner (7 ex. FSCA); Columbia Co., O’Leno State Park, 12.ii.1966, leg. F.W. Mead (1 ex. FSCA); Highlands Co., Archbold Biol. Sta., 24.iv.1976, leg. L.L. Lampert Jr. (1 ex. FSCA); Hillsborough Co., 6 mi N Tampa, 3.vi.1978, leg. R. Milton (1 ex. FSCA); Leon Co., SR 373 1 mi SW SR 371, Tallahassee, 16.x.1976 (1 ex. FSCA); Liberty Co., Torreya State Park, 15.v.1970, leg. H. Greenbaum, blacklight/sheet (1 ex. FSCA); Torreya State Park, 25.v.1980, leg. J. Watts, attr. To U.V. (1 ex. FSCA); Georgia: Rabun Co., lake in BRM St. Pk., 2.vii.1982, leg. F.N. Young, #2965 (3 ex. FSCA); Indiana: Brown Co., nr Crooked Creek, 1.x.1977, leg. F.N. Young (1 ex. FSCA); Crawford Co., Grantsburg, 18.vii.1965, leg. D. Eckert, Blacklight trap (3 ex. FSCA); Ford Co., New Albany, 5.vii.1966, leg. C.E. White, Blacklight trap (2 ex. FSCA); Imperanon Co., 18.viii.1987, leg. N.M. Downie (1 ex. FSCA); Johnson Co., Peoga, 6.v.1966, leg. E. White (7 ex. FSCA); Knox Co., White River, nr Kinora, 12.ix.1964, leg. F.N. Young, #2168 (1 ex. FSCA); Slough along White River, at Edwardsport, 15.iv.1960, leg. F.N. Young, #1687 (1 ex. FSCA); Marion Co., Indianapolis, 15.vii.1963, leg. E. White (1 ex. FSCA); Camp Belzer, BSA, Indianapolis, 12.vii.1966, leg. C.E. White (2 ex. FSCA); Monroe Co., Bloomington, 6.v.1953, leg. R.M. Laycock (1 ex. FSCA); Bloomington, 2.vi.1991, leg. F.N. Young, BLT (1 ex. FSCA); Posey Co., Hovey Lake, 15.viii.1965, leg. C.E. White, Blacklight trap (3 ex. FSCA); Iowa: Boone Co., Ledges State Park, 2.v.1955, leg. M.D. Huffman (3 ex. FSCA); same as previous except: 2.v.1985 (1 ex. FSCA); same as previous except: 1.x.1961, leg. J.J. Dinsmore (3 ex. FSCA); same as previous except: 1.xi.1961 (1 ex. FSCA); Linn Co., Cedar Rapids, “1536” (1 ex. MTEC); Plymouth Co., Le Mars, 12.v.1965, leg. B. Perrill (1 ex. FSCA); Story Co., Ames, 15.iv.1930, leg. H.B. Mills (2 ex. MTEC); same as previous except: 24.iv.1939, leg. C. Haight (3 ex. MTEC); Kansas: Douglas Co., Lawrence, 24.ix.1921, leg. C. Brown (2 ex. FSCA); Maryland: Kent Co., Chestertown, 13.v.1969, leg. T.E. Rogers (1 ex. FSCA); Montgomery Co., Seneca, 27.v.1951, leg. G.H. Nelson (2 ex. FSCA); Prince George’s Co., College Park, 17.iv.1948, leg. B.K. Dozier, in pond (2 ex. FSCA); College Park, 29.iv.1948, leg. H.L. Dozier (1 ex. FSCA); College Park, 14.x.1948, leg. R. Mansueti (1 ex. FSCA); College Park, 25.iv.1953, leg. G.H. Nelson, to light (1 ex. FSCA); Massachusetts: Norfolk Co., Dedham, 11.vi.1920 (1 ex. FSCA); Minnesota: Morner Co., nr Grand Meadow, roadside park, 18.viii.1965, leg. R.H. Arnett, in dammed pond (13 ex. FSCA); Morula Co., nr Grand Meadow, 18.viii.1965, leg. R.H. Arnett Jr., roadside park in damned pond (40 ex. FSCA); Mississippi: Marshall Co., Byhalia, 10.v.1983, leg. L.R. Davis Jr., 11:15PM at lights (1 ex. FSCA); Missouri: Calloway Co., 3 mi W Portland on Rt 94, temp pool, 12.vii.1973, leg. S.O. Swadener, Lot No.730712A (1 ex. FSCA); Carter Co., Van Buren, 22.vi.1955 (2 ex. FSCA); Clay Co., nr Missouri River, E of Birmingham, 2.v.1968, leg. J.R. Heitzman (1 ex. FSCA); Dent Co., Montauk St. Pk., 18.v.1978, leg. S.O. Swadener, Lot No.730518-A (1 ex. FSCA); Douglas Co., Cartwright Tree Farm, 10 mi E of Cabool, walnut, apple, & peach orchards, Deciduous Ozark Forest, open fields & Indian Creek, 14.vii.1991, leg. H.M. Webber, at U.V. light (1 ex. FSCA); Franklin Co., 3.vii.1978, leg. K. Jackson, in lake (1 ex. FSCA); same as previous except: at light (1 ex. FSCA); Green Co., Willard, 6.vii.1929, leg. K. Nime, pond (1 ex. FSCA); Jackson Co., Adair Park, Independence, 3.v.1968, leg. J.R. Heitzman (1 ex. FSCA); Vernon Co., Nevada, 10.v.1964, leg. D&J. McReynolds, (1 ex. FSCA); same as previous except: 8.vi.1964 (1 ex. FSCA); same as previous except: 9.v.1972, leg. J.W. McReynolds (1 ex. FSCA); Montana: Wibaux Co., pond 30 mi N Wibaux, 27.vii.1990, leg. D.L. Gustafson (2 ex. MTEC); Nebraska: Cherry Co., McKelvie Nat’l For., 30 mi WSW Valentine, 9.vii.1998, leg. A. Ramsdale, at blacklight, at forest margin near sand hills prairie, night (1 ex. MTEC); New Jersey: Gloucester Co., Paulsboro, 11.vi.1961, leg. H.L. Dozier (1 ex. FSCA); Ocean Co., Lakehurst, 1.viii.1960, leg. H.L. Dozier (1 ex. FSCA); New York: Schuyler Co., Texas Hollow State Wildlife Area, 1.ix.1999, leg. K.B. Miller (5 ex. MSBA); Westchester Co., White Plains, 14.v.1922, leg. E.H.P. Squire, (1 ex. FSCA); same as previous except: 20.v.1923 (1 ex. FSCA); same as previous except: 31.v.1923 (3 ex. FSCA); 10.vi.1923 (4 ex. FSCA); North Carolina: Jackson Co., Balsam, 6.v.1965, leg. W. Rosenberg (1 ex. FSCA); Macon Co., Watuaga Valley, 28.viii.1987, leg. F.N. Young, #3247A (1 ex. FSCA); Wake Co., Raleigh, Yates Pond, 12.ix.1970, leg. L.L. Lampert (8 ex. FSCA); North Dakota: Ransom Co., McLeod, 25.vii.1960, leg. J. Onsager (1 ex. MTEC); Ohio: Delaware Co., 4.x.1958, leg. E.I. Hazard (2 ex. FSCA) Franklin Co., Columbus, 20.v.1984, leg. M.A. Ivie (1 ex. MTEC); same as previous except: 1.viii.1985, leg. R.S. Miller (9 ex. MTEC); same as previous except: 7.viii.1985 (18 ex. MTEC); Columbus, Mere Pond, 23.viii.1985, leg. R.S. Miller (32 ex. MTEC); Lucas Co., nr West Toledo, Schwamberger Prarie, 10.vi.1984, leg. J.B. Stribling, UV light (1 ex. MTEC); Williams Co., Mudlake, 18.vii.1984, leg. J.A. Shuey (1 ex. MTEC); Muskingum Co., Zanesville, 2.v.1920, leg. A.E. Miller (3 ex. FSCA); Ross Co., Chillicothe, 1.viii.1992, leg. A.E. Miller (3 ex. FSCA); Oklahoma: Catoosa, 26.iv.1938, leg. E.K. Waering (1 ex. FSCA); same as previous except: 26.iv.1939 (1 ex. FSCA); same as previous except: 27.iii.1939 (1 ex. FSCA); Comanche Co., Ft. Still, 20.vi.1974, leg. T.E. Rogers (2 ex. FSCA); Latimer Co., 5 mi W Red Oak, v.1980, leg. K.H. Stephan (1 ex. FSCA); Latimer Co., 5 mi W Red Oak, ix.1980, leg. K.H. Stephan (10 ex. FSCA); Payne Co., Stillwater, 14.vii.1976 (1 ex. FSCA); nr Lake Carl Blackwell, 16.viii.1976 (1 ex. FSCA); South Carolina: Greenville Co., Greenville, 9.ix.1954, leg. H.L. Dozier (1 ex. FSCA); Newberry Co., 12.v.1968, leg. L.L. Lampert (1 ex. FSCA); Newberry Co., Jalapa, 24.iv.1973, leg. L.L. Lampert, light (1 ex. FSCA); Tennessee: Cuba, 25.v.1964, leg. K. Stephan (1 ex. FSCA); Obion Co., Reelfoot Lake S. P., 1/2 mi SE of Samburg, 4.vii.1983, leg. C.P. Withrow (2 ex. MTEC); Texas: Crosby Co., White River Lake, SW Area, 24.ix.1997, leg. Wappes & Huether (1 ex. FSCA); Runnels Co., Miles, 28.vi.1939, leg. H. Wilee Jr. (1 ex. FSCA); Waxahachie Co., Atlanta, 26.v.1964, leg. K. Stephan (1 ex. FSCA); Virginia: Rockingham Co., Craney Island, 7.x.1984, leg. C.L. Staines Jr. (1 ex. FSCA); West Virginia: Pocahontas Co., Cranberry Glades, 1213-1219 m, 27.vi.1967, leg. H.V. Weems, blacklight (1 ex. FSCA); Wisconsin: Dane Co., 18.v.1952, leg. D.H. Habeck (1 ex. FSCA).

No locality information: “Station.”, 8.v.1901, “Hatch Ex.” (1 ex. MTEC); “E-2” (1 ex. FSCA).

Male (Fig. 8C–D): Size: 9.93–11.1 mm. Body form narrowly oval; elytral apices with sutural angle produced into a point, rarely with point reduced and elytra appearing completely rounded, elytral striae faint basally becoming more evident apically and laterally; profemora without sub-apicoventral tooth; protibia wedgeshaped, without distolateral margin produced; mesotarsal claws similar in size, with ventral margin straight; venter darkly colored, reddish brown to black often with a metallic shine present, epipleura similarly colored as thorax and abdomen; Aedeagus (Fig. 9A, B, D) median lobe in dorsal view acuminate in apical 1/5, apex narrowed and shortly rounded, in lateral view apex of median lobe barely curved dorsally, in ventral view sperm-groove parallel sided for near entirety of length, apex flatly rounded, parameres very weakly rounded laterally in apical 1/3.

Female (Fig. 8A–B): Size: 10–11.3 mm. Body form narrowly oval; elytral apices produced and rounded, with sutural angle produced into a point, apicolateral sinuation strong, elytral striae faint basally, becoming more evident apically and laterally; profemora without sub-apicoventral tooth; protibiae laterally weakly curved, distolateral margin not expanded; venter darkly colored, reddish brown to black, often with metallic luster, epipleura similarly colored as thorax and abdomen.

Figure 8. 

Dineutus assimilis. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus D ♂ ventral habitus. All scale bars ≈ 2 mm.

Figure 9. 

Dineutus assimilis. A aedeagus dorsal view B aedeagus ventral view C ♂ mesotarsal claws D aedeagus lateral view. Scale bar for C ≈ 0.10 mm all others ≈ 1 mm.

Dineutus assimilis is unique among all North American species of Dineutus in the narrowly elongate oval body form, both sexes with the elytral apices more or less regularly rounded with the sutural angles produced, males with the profemora without a sub-apicoventral tooth, a wedge shaped protibia, mesotarsal claws that are similar in shape with their ventral margins straight, and the form of the aedeagus. The species most similar to D. assimilis are D. hornii and D. nigrior, especially in the form of the females. Males of D. assimilis can be separated from D. hornii by the sutural angle of the elytra being regularly produced to a point, although rarely some individuals have the point reduced giving the elytra a regularly rounded look similar to those of D. hornii. In such cases, specimens of D. assimilis can be distinguished by the elytral epipleura being colored similarly to the adjacent thoracic and anterior abdominal ventrites (Fig. 8D), in contrast with D. hornii in which the epipleura is different in color (much lighter) from the rest of the venter (Fig. 18D). The mesotarsal claws can also be used to separate males of D. assimilis (Fig. 9C) from D. hornii (Fig. 19C). In D. assimilis the ventral margins of the claws are straight, whereas in D. hornii they are very shallowly curved. Dineutus assimilis also have the ultimate antennomere angled, whereas in D. hornii the antennal flagellum is short and thick, with the ultimate antennomere rounded. Males of Dineutus assimilis can be separated from D. nigrior in their smaller size (9.9–11.3 mm), more narrow body form, and, most readily, by the mesotarsal claws which are similar in size with straight ventral margins, whereas in D. nigrior the mesotarsal claws are distinctly asymmetrical with the anterior claw larger than the posterior and both having the ventral margins shallowly curved. The most reliable way to distinguish between D. assimilis, D. hornii and D. nigrior is the aedeagus. The median lobe of the aedeagus of D. assimilis (Fig. 9A) is acuminate in the apical 1/5. The aedeagi of both D. hornii and D. nigrior are more elongate and parallel sided with the median lobe apically narrowed but not acuminate.

Females of D. assimilis are more difficult to differentiate from D. hornii and D. nigrior. Females of D. assimilis differ from those of D. hornii in the epipleura color being similar to the adjacent thoracic anterior abdominal ventrites, whereas in D. hornii the epipleura are lighter in color than the surfaces of the thorax and abdomen (Fig. 18B). The elytral apices of the females of D. assimilis are more similar to those of D. nigrior. In general D. assimilis is smaller (10–11.3 mm) than D. nigrior, and also more narrowed in body form. The most reliable way to separate D. assimilis from D. nigrior is the distal lateral margin of the protibiae. In D. assimilis the distal lateral margin is not produced laterally (Fig. 8B), but continuously weakly curved, whereas in D. nigrior the margin is laterally weakly expanded (Fig. 31B).

(Fig. 52A). Southern Canada from British Columbia to Nova Scotia (Majka 2008; Roughley 1991; Webster and DeMerchant 2012), and east of the Rocky Mountains in the U.S.A. as far south as Texas and Northern Florida (Epler 2010; Ferkinhoff and Gunderson 1983; Folkerts 1978; Gordon and Post 1965; Hilsenhoff 1990; Malcolm 1971; Régimbart 1907; Roberts 1895; Sanderson 1982; Whiteman and Sites 2003; Wood 1962).

This is most widespread and commonly encountered species of Dineutus in North America, occupying both lotic and lentic habitats (Woods 1962; Hilsenhoff 1990; Whiteman and Sites 2003). The first author has collected this species in a secondary growth deciduous forest, Baldwin Woods, near Baldwin, Kansas, in a large forest pond with a muddy bottom, with plenty of leaf detritus and several fallen emergent trees. Here D. assimilis was found in large numbers near the shore, with others often exploring deeper regions of the pond. In New Brunswick, Canada, D. assimilis was collected in similar habitats, the margins of ponds with emergent vegetation within forests composed of red oak and red maple (Webster and DeMerchant 2012). Webster and DeMerchant (2012) also found D. assimilis in black spruce and tamarack bogs. This species has also been collected in other lentic situations from the Prairie Region of Missouri, where Whiteman and Sites (2003) found specimens associated with the following plant taxa: Brasneia, Ceratophyllum, Juncus, Lespedeza, Ludwigia, Polygonum, Potamogeton, Sagittaria, Typha, Cyperaceae, and Poaceae. This species also comes to ultraviolet light (Webster and DeMerchant 2012).

Dineutus assimilis is the most commonly encountered species of Dineutus in North America, and has one of the largest ranges of any North American species (Fig. 52A), often erroneously listed under the name D. americanus, even recently (e.g. Ciegler et al. 2003). As early as 1927, Ochs (1927b) had the types of D. americanus examined by an associate in London, and determined unambiguously that D. americanus is the Caribbean species, with D. assimilis found in mainland North America. We have again confirmed, after examination of the syntype of D. americanus, that D. assimilis is not D. americanus of Linnaeus. It is likely all records of D. americanus from areas not in the Caribbean or the Florida Keys actually represent D. assimilis. An example of references clearly referring to D. assimilis is Zuellig et al. (2002), who recorded “D. americanus” from Wyoming. Hatch’s (1927) key to the larvae of “D. americanus” most likely refers to D. assimilis as well.

The juvenile stages have been formally described and illustrated by Wilson (1923) and sparse life history information is available in Smith (1926) and Istock (1966; 1967).

South Carolina.

199

Dineutus carolinus LeConte, 1868: syntype (♀ pinned) “[orange disc]// Type/ 6093 [orange label Type typed in black ink, 6093 handwritten in black ink]// D. carolinus/ Lec. [white label handwritten in black ink, handwriting appears to be LeConte’s]// LECTOTYPE/ Dineutus carolinus/ Desig. R.P. Withington III/ 1998 [red label, handwritten in black ink]//” deposited in MCZ.

Dineutus carolinus mutchleri Ochs, 1924: holotype (♂, pinned) “Nassau, Bahamas, V-VI-1917/Wm. M. Mann Collector//Amer. Mus. Nat. Hist., Dept. Invert. Zool., No.28070/HOLOTYPE/Dineutus carolinus LeC. subsp. mutchleri OchsType ! ♂/Dineutus carolinus LeConte 1868. Det: L. Cook 2005” AMNH type catalogue No. 433.

BAHAMAS:Eleuthera Island: Rainbow Bay, 4.vii.1989, leg. D.B. & R.W. Wiley (1 ex. FSCA); Rainbow Bay, 21-28.iv.1984, leg. J.R. Wiley (6 ex. FSCA); Grand Bahamas Island: Freeport, 21.xii.1984, leg. S. Dunkle (4 ex. FSCA); Great Exuma: Simons Pt., “23.31.50-75.47.30”, 13.i.1980, leg. S.A. Teale (1 ex. KSEM); same as previous except: 21.i.1980 (1 ex. KSEM); same as previous except: 26.i.1980 (3 ex. KSEM); New Providence: 1.viii.1959, leg. J.B. Rearle (1 ex. FSCA); South Bimini: 14.vi.1967, leg. B.K. Dozier (2 ex. FSCA). U.S.A.:Arkansas: Washington Co., Devil’s Den State Park, pond, 6.viii.1975, leg. D. Huggins, SEMC 1054952 (1 ex. KSEM); Florida: Alachua Co., 10.ii.1949, leg. S.B. Mansell (5 ex. FSCA); same as previous except: 19.ii.1949, leg. B.W. Cooper (1 ex. FSCA); same as previous except: 8.iv.1949, leg. B.W. Cooper (2 ex. FSCA); same as previous except: 8.iv.1949, leg. E.H. McConkey (7 ex. FSCA); same as previous except: 19.iv.1949, leg. W.L. Jennings (1 ex. FSCA); same as previous except: 17.ii.1950, leg. O.G. Fogle (1 ex. FSCA); same as previous except: 15.iv.1950, leg. E.W. Michelson (1 ex. FSCA); same as previous except: 18.iv.1951, leg. J.E. Brogdan (1 ex. FSCA); same as previous except: x.1960, leg. S. Cabler (1 ex. FSCA); same as previous except: 4.ix.1989, leg. M.L. May (1 ex. FSCA); Gainesville, 20.iii.1987, leg. Willis, ACC.76-77; ACC.79-83; ACC.86; ACC.88 (9 ex. FSCA); Gainesville, 21.iii.1978, leg. L.R. Davis Jr., (2 ex. FSCA); same as previous except: 5.v.1978, leg. M.C. Thomas (1 ex. FSCA); same as previous except: 11.v.1978 (1 ex. FSCA); same as previous except: 2.vi.1978 (1 ex. FSCA); same as previous except: 18.iv.1983, leg. N. Hastettle (1 ex. FSCA); same as previous except: 5.vi.1983, leg. L.R. Davis Jr. (1 ex. FSCA); 5.vi.1959, leg. H.V. Weems Jr., taken at light (1 ex. FSCA); Gainesville, Beville Hts., 5.vii.1980, leg. L.A. Stange, Blacklight trap (1 ex. FSCA); NW Gainesville, 27.iii.1974, leg. J.B. Heppner, at blacklight (7 ex. FSCA); Gainesville, 3517 NW 10th Ave., 1.vi.1993, leg. R.E. Woodruff, Blacklight trap (8 ex. FSCA); 2 mi NW Gainesville, 20.iv.1974, leg. J.B. Heppner, blacklight (4 ex. FSCA); 6 mi SW Gainesville, 4.xi.1974, leg. L.R. Davis Jr., BLT (1 ex. FSCA); same as previous except: 5.xi.1974 (2 ex. FSCA); same as previous except:17.xi.1974 (1 ex. FSCA); same as previous except: 19.xi.1974 (2 ex. FSCA); Bainsville, 24.iii.1983, leg. C. Blare (1 ex. FSCA); Hatchet Creek, 25.vii.1975, leg. J.B. Heppner (3 ex. FSCA); O’Leno State Park, 8.viii.1997, leg. J. Cicero (3 ex. FSCA); Hogtown Creek, 28.vi.1975, leg. J.B. Heppner (1 ex. FSCA); Clay Co., Hibernia, 7.viii.1939, leg. J.D. Beamer (1 ex. KSEM); Collier Co., Copeland, 27.iv.1972, leg. H. Flaschka (1 ex. FSCA); Naples, 27.iv.1984, leg. R.A. Belmont, u.v. blacklight trap (1 ex. FSCA); Naples, 13.v.1984, leg. R.A. Belmont (4 ex. FSCA); Naples, 15.xii.1985, leg. R.S. Miller (1 ex. MTEC); Columbia Co., O’Leno State Park, 12.ii.1966, leg. F.W. Mead (1 ex. FSCA); O’Leno State Park,11.xii.1954, leg. C.N. Patton (1 ex. FSCA); Dade Co., nr Everglades Nat. Prk., fresh water, 7.v.1955, leg. D.K. Caldwell, K13 (8 ex. FSCA); Dade Co., Camp Mahachee, nr. Matheson Hammock, 27.iv.1983, leg. M.C. Thomas & L. Parker, Blacklight trap (2 ex. FSCA); Homestead, 28.v.1958, leg. D.O. Wolfenbarer, Blacklight trap (1 ex. FSCA); 25 m W Miami, 23.vii.1934, leg. P. McKinstry (1 ex. KSEM); 25 m W Miami, 23.vii.1934, leg. M.E. Griffith (1 ex. KSEM); Ross-Castello Hammock, 1.v.1968, leg. R.H. Arnett, Blacklight trap (1 ex. FSCA); Miami Springs,15.vi.1961, leg. C.E. White (1 ex. FSCA); Dixie Co., Horseshoe Beach, 28.vii.1985, leg. P. Van Mierop, pond (1 ex. FSCA); Escambia Co., Pensacola, 17.v.1960, leg. R.E. Woodruff, col. At light (1 ex. FSCA); Gadsden Co., Rocky Comfort Creek, 4 mi S Hwy 268,13.v.1980, leg. G.B. Wibmer, uv light (1 ex. FSCA); Gulf Co., St. Joseph T.H. Stone Memorial State Park, 14.vi.1969, leg. H.V. Weems Jr. (1 ex. FSCA); Henderson Co., Fletcher, 10.vii.1979, leg. L.L. Lampert, U.V. Light (1 ex. FSCA); Hernando Co., Weekiwachee Spring, 3.vi.1954, leg. W.C. Sloan, Sta.4 (2 ex. FSCA); Highlands Co., Archbold Biol. Sta., 7.iv.1975, leg. L.L. Lampert, UVL (1 ex. FSCA); same as previous except: 18.xi.1982, leg. L.L. Lampert Jr., UVL (1 ex. FSCA); same as previous except: 19.iv.1976, leg. L.L. Lampert Jr. (1 ex. FSCA); same as previous except: 23.vi.1988, leg. K.E.M. Galley, at blacklight SE tract (2 ex. FSCA); same as previous except: 19.iii.1968, leg. C.E. White, at blacklight trap (2 ex. FSCA); same as previous except: 10.ii.1993, leg. M.J. Rothschild (1 ex. FSCA); Highlands Co., Highlands Hammock State. Prk., 9-10.viii.1983, leg. K.W. Vick, Blacklight trap (1 ex. FSCA); same as previous except: 11.viii.1983 (1 ex. FSCA); Hillsborough Co., Hillsborough RI St. Pk., 9-10.viii.1983, leg. K.W. Vick, Blacklight trap (5 ex. FSCA); Plant City, 20.vi.1926, leg. C. O. Bare (1 ex. KSEM); Indian River Co., nr. Vero Beach, 12.iv.1983, leg. K. Hibbard (3 ex. FSCA); Lake Co., 26.iv., leg. E.M. Davis, (3 ex. FSCA); Leon Co., Springhill Rd., nr. Airport, 16.x.1980, leg. B. Lenczerski (1 ex. FSCA); Liberty Co., Yellow Creek SE of Telogia, 5.ix.1990, leg. F.N. Young, #3435 (1 ex. FSCA); same as previous except: 7.x.1992, #3503 (1 ex. FSCA); Torreya State Park, 16.v.1970, leg. H. Greenbaum, blacklight/sheet (1 ex. FSCA); Marion Co., 1-75 & Rte. 44, 12.iii.1988, leg. L.R. Davis Jr. & M. L. Benoit, at light (1 ex. FSCA); Village of Rainbow Springs, 3-7.vii.1982, leg. M.C. Thomas (2 ex. FSCA); Ocala, 5.viii.1975, leg. T. Rogers (1 ex. FSCA); Big Pine Key, 15.iii.1947, leg. L.D. Beamer (1 ex. KSEM); Okaloosa Co., 3 mi S. of Holt Log Lake Bridge, 4.x.1966, leg. P.A. Thomas (3 ex. FSCA); Palm Beach Co., 28.xi.1947, leg. McRae (1 ex. FSCA); Palm Beach Co., 3 mi N Bell Grande, 13.xii.1985, leg. R.S. Miller (2 ex. MTEC); Saint Lucie Co., White City,1.iv.1983, leg. K. Hibbard (2 ex. FSCA); U.S.A.: Georgia: Okefenokee Swamp, 30.vii.1934, leg. E. Griffith (2 ex. KSEM); same as previous except: 8.iii.1934, leg. P.A. McKinstry (1 ex. KSEM); Decantur Co., 1 mi W Recovery, 18.viii.1953, leg. F.N. Young, #986 (2 ex. FSCA); Kansas: Labette Co., Altamont, 5 mi E, Labette Creek, 22.vi.1974, SEMC 1054951 (1 ex. KSEM); Louisiana: St. John the Baptist, Edgard, 6.iii.1973, leg. V. Brou (2 ex. FSCA); same as previous except: 9.iii.1973 (1 ex. FSCA); same as previous except: 11.iii.1973 (2 ex. FSCA); same as previous except: 30.iii.1973 (1 ex. FSCA); same as previous except: 14.iv.1973 (2 ex. FSCA); 19.iv.1973 (1 ex. FSCA); same as previous except: 15.vi.1973 (2 ex. FSCA); same as previous except:13.vii.1973 (1 ex. FSCA); East Baton Rouge, Baton Rouge,19.x.1929, leg. H.A.S. (1 ex. MTEC); same as previous except: 31.vii.1961, leg. G.N. Ross (1 ex. FSCA); Madison, Tallulah, 7.vii.1930, leg. H. Mills (1 ex. MTEC); Maryland: Worcester Co., Pocomoke City, 22.ix.1984, leg. C.L. Staines Jr. (1 ex. FSCA); North Carolina: Carteret Co., Walker Mill Pond, 15.iii.1990, leg. J.B. Sullivan (1 ex. FSCA); Craven Co., North Harlowe, 18.vii.1990, leg. J.B. Sullivan (1 ex. FSCA); Jackson Co., Balsam, 2.v.1965, leg. W. Rosenberg (1 ex. FSCA); Oklahoma: Payne Co., nr Lake Carl Blackwell, 16.viii.1976 (1 ex. FSCA); Texas: Colorado Co., 3.iv.1922, leg. G. Wiley, “U of X Lot 1108” (3 ex. KSEM); Colorado Co., 18.v.1922, leg. G. Wiley (1 ex. KSEM); Montgomery Co., Woodlands, 2.vi.1979, leg. J.E. Wappes (3 ex. FSCA); same as previous except: 3.v.1980 (1 ex. FSCA); Walker Co., “Strawn”, 7.iii.1952, leg. T. Pyburn, “Green Branch” (1 ex. FSCA); Virginia: Middlesex Co., Warner, 13.x.1983, leg. C.L. Staines Jr. (1 ex. FSCA).

Male (Fig. 10C–D): Size: 9.1–10.9 mm. Body form elongate oval; elytral apices regularly rounded, with serrations and irregularities present apically, elytra with reticulation strong laterally and apically, medial disc with reticulation sparse or absent, striae faintly present, most evident medially on elytral disc, lateral marginal depression of elytra evident, narrow in humeral region, expanded posteriad, usually extending to lateral elytra apex; profemora with small sub-apicoventral tooth atop profemoral carina; protibiae subsinuate, distolateral margin flatly angled and weakly expanded; mesotarsal claws (Fig. 11F) with ventral margin weakly rounded; venter darkly colored, reddish brown to black, mesothoracic and metathoracic legs usually lighter in coloration, as well as apex of abdomen; Aedeagus (Fig. 11A) with median lobe in dorsal view nearly to as long as parameres, widest basally and regularly narrowed apically, more narrowed in apical 1/3, in some individuals much more noticeably narrowed in the apical 1/3, apex very shortly rounded, in lateral view median lobe sinuate ventrally in apical 1/3, parameres parallel-sided, broadly rounded apically.

Female (Fig. 10A–B): Size: 8.7–10.6 mm. Body form elongate oval; elytral apices regularly rounded, with serrations and irregularities present apically, apicolateral sinuation usually present, sometimes very strongly developed, elytra with reticulation strong laterally and apically, medial disc with reticulation sparse or absent, striae faintly present, most evident medially on elytral disc, lateral marginal depression of elytra evident, narrow in humeral region, expanded posteriad, usually extending to lateral elytra apex; profemora without sub-apicoventral tooth; protibiae weakly subsinuate, distolateral margin flatly angled; venter darkly colored, reddish brown to black, mesothoracic and metathoracic legs usually lighter in coloration, as well as apex of abdomen.

Figure 10. 

Dineutus carolinus. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus D ♂ ventral habitus. All scale bars ≈ 2 mm.

Figure 11. 

Dineutus carolinus. Bahamas specimen aedeagus A dorsal view B ventral view C lateral view; Florida specimen aedeagus D dorsal view E ventral view F ♂ mesotarsal claws G aedeagus lateral view, Texas specimen aedeagus H dorsal view I ventral view J lateral view. Scale bar for F ≈ 0.10 mm all others ≈ 1 mm.

Dineutus carolinus is unique among North American Dineutus in having both sexes elongate oval and the elytra with a distinct lateral marginal depression, the elytral apices regularly rounded with serration and irregularities present, males with the profermoral sub-apicoventral tooth small and often atop a short carina, the male mesotarsal claws with the ventral margin rounded, and the unique shape of the aedeagus. The species most similar to D. carolinus are D. emarginatus, D. solitarius, and D. americanus.

Both sexes of D. carolinus can be separated from D. emarginatus by the elytra apices being more narrowly rounded with serrations and/or irregularities present. The presence of serrations, however, can be variable. In some individuals it is somewhat evident at the sutural margin, but others lack serrations entirely, having only roughened irregularities. The microreticulation of the elytra of D. carolinus tends to be much more coarse laterally and the medial disk of the elytra often lacks reticulation, whereas D. emarginatus tends to have fine microreticulation covering the entire elytra. Although not as reliable, the ventral coloration differs between the two species. In D. carolinus the entire venter tends to be more reddish brown whereas it is regularly black in D. emarginatus. The dorsal coloration of the two species is very similar.

Males of D. carolinus can fairly easily be separated from D. emarginatus by the profemoral sub-apicoventral tooth small atop a profemoral carina, rather than large and triangular. Also, in D. carolinus the mesotarsal claws have the ventral margins rounded, rather than straight as in D. emarginatus. The aedeagus is the best way to identify D. carolinus. The median lobe of D. carolinus is regularly narrowed for much its length, until the apical 1/3 where it is more strongly narrowed, but not strongly acuminate as in D. emarginatus. Females of D. carolinus are more difficult to separate from D. emarginatus. The best way to distinguish them aside from the more narrowly rounded elytral apices with serrations and/or irregularities in D. carolinus is the presence of an apicolateral sinuation in the elytra. This sinuation is nearly always present and well-developed in D. carolinus, although in some females it is sometimes weakly developed or absent. Dineutus emarginatus females nearly always have this sinuation absent, but at most only weakly developed.

Members of Dineutus carolinus of both sexes can be distinguished from D. solitarius by more elongate oval body form, the pronotum more narrow with the lateral margins more narrowly angled basally to apically, and the elytral apices more narrowly rounded apically with serrations and irregularities present. Dineutus carolinus of both sexes also have the lateral marginal depression of the elytra present, which is not evident in D. solitarius. Males of D. carolinus differ from those of D. solitarius by the mesotarsal claws with the ventral margin curved, unlike D. solitarius that have the ventral margins straight. The aedeagus of D. carolinus is tapered but not acuminate, whereas that of D. solitarius is acuminate. Females of D. carolinus can also be separated from those of D. solitarius by the apices of the elytra laterally sinuate, whereas in D. solitarius they are usually evenly rounded without an apicolateral sinuation, and if a sinuation is present, it is very weakly developed.

Dineutus carolinus can be separated from D. americanus by the differences provided under the differential diagnosis for D. americanus.

(Fig. 53A). Mainly known from the southeastern half of the United States (Epler 2010; Folkerts 1978; Régimbart 1907; Roberts 1895), as far south as the extreme northeast corner of Mexico (Wood 1962), and east into the Caribbean where it is primarily known from Nassau (Young 1953), the range is here extended to the southeast as far as Great Exuma Island.

This species appears to be primarily lentic (Young 1953, 1954). Dineutus carolinus occurs in Florida and is characteristic of small upland and flatwoods ponds, only rarely being found in slow streams with ample vegetation (Young 1954). The first author has collected D. carolinus in slow moving mud bottomed streams and bayous in southeastern Texas.

Dineutus carolinus is the only species of Dineutus well established across much of continental North America as well as in the western Caribbean where its range overlaps with that of D. americanus. The two species are fairly similar.

The Caribbean subspecies D. c. mutchleri was described by Ochs (1924), from Nassau (Bahamas), who used several characters to separate it from the mainland subspecies including, size and number of setigerous femoral punctures, as well as aedeagal shape. Size shows overlap and is not discrete. Number of setigerous punctures is known to vary among populations, especially with size (pers. obs.; Wood 1962). Ochs (1924) described differences in the aedeagus comparing it to the illustration provided by Roberts (1895), but the aedeagus of specimens examined from the Bahamas are identical to that of the mainland populations. We found the aedeagus of the Bahaman specimens to be nearly identical to those from mainland Florida and elsewhere (Fig. 11). Young (1953) also noticed the similarity and suggested that the drawing by Roberts (1895) was actually from an undescribed form in Texas. Ochs (1929) also mentions having compared the Bahaman specimens of D. c. mutchleri to specimens of D. carolinus from Texas, and that those showed greater differences than the Bahaman form.

Having examined some specimens of D. carolinus from Texas (FSCA) there is some variation, but not much from other populations of D. carolinus. A single male specimen examined from Texas has minor variation in the aedeagus from other mainland specimens (Fig. 11H), which may explain Roberts (1895) illustration. This specimen has the apical 1/3 of the median lobe more strongly narrowed (Fig. 11H) than other populations of D. carolinus (Fig. 11A–E, G) from the mainland. The median lobe of the Texas D. carolinus is nearly as long as the parameres, which are very parallel-sided and flatly rounded, similar to other populations of D. carolinus (Fig. 11). Although Roberts (1895) illustration shows the strong narrowing, it also indicates the median lobe shorter than the parameres, which is not the case in our specimen. The parameres in Roberts (1895) illustration, however, match well with our specimen. Therefore, it may be that Roberts (1895) drew the aedeagus with the median lobe out of proportion, or, more likely, he drew the median lobe slightly flexed dorsally as happens sometimes during eversion or relaxing of the aedeagus. Externally the male from Texas is very similar to males of other populations. The females of D. carolinus from Texas populations vary more so than male specimens from Texas, when compared to populations outside of Texas. The females are much more broad in appearance, having the pronotal and elytral margins more broadly rounded laterally. In lateral view the females are also slightly more dorsoventrally convex than other D. carolinus females. The increased convexity of the elytra causes the lateral marginal depression to be more shallowly impressed in comparison to other populations. The microreticulation of the elytra also shows variation being much more well-impressed, covering nearly all of the elytra and the pronotum. The elytral apices of Texas D. carolinus females are more broadly rounded and do not have the normal lateral sinuation seen in other populations, but have the apices laterally angled or simply regularly meeting the rounded apices, and the apical serrations and irregularities are highly reduced although, under careful observation, present. All of these variations, however, are well within the typical range of variation within other species of Dineutus and it is our judgment that the populations from Texas are not differentiated enough to merit a formal taxonomic name. The specimens examined from Texas were from the southeastern part of the state, in Montgomery County, near The Woodlands, north of Houston (FSCA).

Ochs (1929) also admits that after having examined more D. carolinus from Florida and Georgia, that D. c. mutchleri are much more similar to these populations of D. carolinus than the Texas forms which he used as a comparison during description of D. c. mutchleri. It does appear that the Texas specimens are the most distinctive of D. carolinus populations, and the populations from the Caribbean formally named as a subspecies by Ochs (1924) are not, in fact, particularly distinctive. Therefore, based on examined specimens from Texas, southeastern U.S., and the Caribbean, we consider Dineutus carolinus mutchleri as a junior subjective synonym of Dineutus carolinus.

East Indies, likely in error. The type is labeled, “Ind.” according to Ochs (1949), which Young (1954) suggested could refer to Indiana, though Forsberg’s (1821) indicated “Indies oriental.”

73

Not examined. Ochs (1925b) examined Forsberg’s types when establishing his synonymies, therefore the identity of D. ciliatus is well established in relation to its most common synonym D. vittatus.

U.S.A.:Alabama: U.S.A.: Alabama: Conecuh Co., 13 km E Evergreen on Hwy 31, Old Town Creek, 31°27.037'N, 86°49.81'W, 53 m, 11.v.2006, leg. K.B. Miller, KBM1105061 (6 ex. MSBA); Marion Co., Barnsville, 23.viii.1931, leg. R.H. Beamer (1 ex. KSEM); Connecticut: New London Co., New London, 16.v.1931, leg. M. Sanderson (1 ex. KSEM); Delaware: New Castle Co., Glasgow, 4.v.1957, leg. L.R. Krusberg (1 ex. FSCA); Louisiana: Beaugarl Co., 13.viii.1928, leg. R.H. Beamer Jr. (4 ex. KSEM); Maryland: Prince George’s Co., College Park, 4.x.1947, leg. B.K. Dozier (6 ex. FSCA); Massachusetts: Hampshire Co., Amherst, 16.vi.1904 (1 ex. MTEC); Norfolk Co., Blue Hills Reservation, v.1929, leg. G.C. Wheeler (1 ex. FSCA); New Jersey: Bergen Co., Dumont Woods, 9.iv.1931, leg. C.L. Ragot (1 ex. FSCA); Bergen Co., Woodcliff Lake, 20.v.1934 (3 ex. FSCA); Gloucester Co., 1 mi S Paulsboro, 3.vii.1959, leg. H.L. Dozier (4 ex. FSCA); Ocean Co., Cassville, branch of Tom’s River, vi.1931, leg. Siepmann (4 ex. FSCA); Lakehurst, 6.v.1934, leg. C.L. Ragot (1 ex. FSCA); New York: Westchester Co., White Plains, 2.x.1921, leg. E.H.P. Squire (1 ex. FSCA); same as previous except: 23.viii.1922 (2 ex. FSCA); same as previous except: 5.ix.1922 (2 ex. FSCA); 10.vi.1923 (19 ex. FSCA); North Carolina: Wake Co., Raleigh, leg. S.P. Whitney (1 ex. FSCA); Oklahoma: Larimer Co., 5 mi W Red Oak, 2.vii.1977, leg. K.H. Stephan (7 ex. FSCA); U.S.A.: Oklahoma: Larimer Co., 5 mi W Red Oak, vii.1980, leg. K.H. Stephan (1 ex. FSCA); Murray Co., Arbuckle Mts., nr Davis, 21.vi.1922 (1 ex. FSCA); Rhode Island: Kent Co., “Greenwich”, 15.vii.1934, leg. W. Sanderson (3 ex. KSEM); South Carolina: Sumter Co., 29.iv.1968, leg. L.L. Lampert, on stream (1 ex. FSCA). No locality information: “Station.”, 8.viii.1901, “Hatch Ex.” (1 ex. MTEC).

Male (Fig. 12C–D): Size: 12.7–14.6 mm. Body form broadly roundly oval; antennal flagellum thick and round, ultimate segment rounded; elytral apices regularly rounded, serration absent, elytra with bronzy lateral stripe disappearing apically, elytral striae weakly developed, 8^th elytral stria without punctures present or strongly evident; profemora without sub-apicoventral tooth; protibiae club-shaped; anterior mesotarsal claw (Fig. 13C) with denticle; venter normally dark reddish brown, rarely reddish orange (teneral individuals); Aedeagus (Fig. 13A, B, D) medial lobe in dorsal view with apicomedial papilla, in ventral view sperm-groove parallel sided, in lateral view median lobe curved, apically narrow, parameres weakly rounded laterally in apical 1/3.

Female (Fig. 12A–B): Size: 11.5–14.6 mm. Body form broadly roundly oval; Antennal flagellum thick and round, ultimate segment rounded; elytral apices regularly rounded, serration absent, elytra with bronzy lateral stripe disappearing apically, elytral striae weakly developed, 8^th elytral stria without punctures present or strongly evident; profemora without sub-apicoventral tooth; protibiae club-shaped; venter normally dark reddish brown, rarely reddish orange (teneral individuals).

Figure 12. 

Dineutus ciliatus. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus D ♂ ventral habitus. All scale bars ≈ 2 mm.

Figure 13. 

Dineutus ciliatus. A aedeagus dorsal view B aedeagus ventral view C ♂ mesotarsal claws D aedeagus lateral view. Scale bar for C ≈ 0.10 mm all others ≈ 1 mm.

This species is most easily distinguished from other members of North American Dineutus by the presence of a bronzy lateral stripe on each elytron, a regularly oval body form, large size, absence of a profemoral sub-apicoventral tooth in the male, and the form of the male aedeagus (Fig. 13A). Dineutus ciliatus is most similar to D. robertsi, but there are several characters that readily separate the two species. Both sexes of Dineutus ciliatus have the venter dark reddish brown in color instead of light yellowish orange (most evident on the epipleura), the antennal flagellum thicker and rounder with the ultimate segment rounded instead of thinner and more parallel sided with an angled ultimate segment, and the 8^th elytral stria with punctures absent or indistinct. The venter coloration of teneral individuals is lighter, reddish orange, but this does not closely approach that of D. robertsi, which is much more yellow in color. Males of D. ciliatus also have the anterior mesotarsal claws with a more weakly developed denticle on their ventral surface, and a smaller general body size than D. robertsi. The aedeagus (Fig. 13) of D. ciliatus has the median lobe narrow and dorsally curved in lateral view with an apicomedial papilla visible in both dorsal and ventral views. The sperm-groove is much more parallel-sided in D. ciliatus than D. robertsi. Finally, the parameres of D. ciliatus are weakly lateral curved in the apical 1/3 instead of strongly curved as in D. robertsi.

(Fig. 53B). Most of the eastern half of the United Sates (Folkerts 1978; Malcolm 1971; Sanderson 1982; Wood 1962; Young 1954).

This is a lotic species (Young 1954; Hatch 1927). In Florida D. ciliatus is commonly found in small, shaded streams, and when found in larger streams prefers to stay near the stream bank (Young 1954). Hatch (1927) describes one habitat of D. ciliatus in Massachusetts as a small sandy bottomed stream, approximately five feet wide and with a depth from six to ten inches, with a flow rate of one foot per second or less. Hatch (1927) also noted that D. ciliatus prefers to reside near the bank of the stream. In east Texas this species was only collected in lotic situations at East Texas Primitive Big Thicket (Realzola et al. 2007). The first author has collected D. ciliatus from both small pebble bottomed forested streams, to larger mud-bottomed rivers, throughout the southeastern United States, where it is quite commonly encountered.

Dineutus ciliatus is a common species with a wide range (Fig. 53B) and is frequently collected and represented in collections in large numbers.

The United States of America

93

Dineutus discolor Aubé, 1838: lectotype, here designated (1 ♀ pinned, missing right protarsus and right mesothoracic leg) “MUSEUM PARIS/ AMÉRIQUE SEPT./ AUDOUIN 1833 [beige label, typed black ink]// green disc [underneath is written in ink is 4117/ 33]// TYPE [white label, typed red ink]// LECTOTYPUS/ P. Brinck designavit 1955. [white label, typed black ink]// LECTOTYPE/ Dineutus discolor/ Desig. RP Withington III/ 1998 [red label, handwritten in black ink]// LECTOTYPE [typed black ink]//” deposited in MNHN.

U.S.A.:Alabama: Marion Co., Barnsville, 23.viii.1931, leg. R.H. Beamer (1 ex. KSEM); Monroe Co., 10 km W Bowles, 31°33.094'N, 86°59.956'W, 11.v.2006, leg. K.B. Miller (1 ex. MSBA); Arkansas: Washington Co., Lake Sequoyah, 7.x.1992, leg. S. Garner (3 ex. MTEC); Florida: Holmes Co., Sandy Creek nr. Ponce de Leon, 11.vi.1978, leg. F.N. Young, #2756 (1 ex. FSCA); Santa Rose Co., Holly Creek at Rd. 260, 6.x.1966, leg. P.A. Thomas, (1 ex. FSCA); Georgia: Jackson Co., Allen Creek, S. Gainesville, 20.viii.1981, leg. F.N. Young, #2887 (1 ex. FSCA); Indiana: Putnam Co., Deer Creek, Manhattan, 19.viii.1969, leg. D.S. White (3 ex. FSCA); Maine: Oxford Co., Paris, 8.vii.1949, leg. C.R. Frost, 2674/ CAF’49 (1 ex. FSCA); York Co., Limington, Saco River, RT.11 at steep falls, 22.vi.1976 (1 ex. FSCA); Maryland: Patapsco River, 30.iv.1935, leg. W.L. Jellison (11 ex. MTEC); Prince George’s Co., Riverdale, 10.i.1910 (1 ex. MTEC) Montgomery Co., 2 mi. E. Silver Spring, N.W. Branch, 20.vii.1951, leg. G.H. Nelson (4 ex. FSCA); Massachusetts: Hampshire Co., Amherst, 24.vii.1967, leg. A Lavallee, (1 ex. FSCA); Norfolk Co., Dedham, 10.vi.1921, leg. G.C. Wheeler (1 ex. FSCA); Missouri: Reynolds Co., Sutton’s Bluff, 9.ix.1978, leg. K. Jackson, in creek (11 ex. FSCA); New Jersey: Raritan River Survey I, ACC Station 3B, 2.vii.1957, leg. T. Dolan (2 ex. KSEM); Middlesex Co., Avenel, 24.iv.1926, leg. Siepman (1 ex. KSEM); New York: New York, 8.v.1892, leg. E.O. Southwick, E.O. Southwick collection (1 ex. MTEC); Greene Co., East Durham, 26.vii.1971, leg. S.E. Thewke (1 ex. FSCA); Westchester Co., White Plains, 1.vi.1924, leg. E.H.P. Squire, (8 ex. FSCA); same as previous except: 8.vi.1924 (1 ex. FSCA); same as previous except: 10.vi.1923 (1 ex. FSCA); North Carolina: Macon Co., small pond in Watauga area n. Franklin, 26.vii.1986, leg. F.N. Young, #3118 (1 ex. FSCA); Moore Co., Mill Creek at Lake View, 7.ii.1966, leg. D.R. Paulson (1 ex. FSCA); Wake Co., 12.ix.1980, leg. R. Hollingsworth (3 ex. FSCA); Wake Co., Raleigh, leg. S.P. Whitney (4 ex. FSCA); same as previous except: 24.ix.1982, leg. R.H. Kenney (1 ex. FSCA); same as previous except: 12.ix.1984, leg. B.S. Bateman (1 ex. FSCA); same as previous except: 11.x.1984, leg. J.L. Williams (1 ex. FSCA); Wake Co., Raleigh, St. Road 1371, SW of Raleigh, 25.vii.1981, leg. S.P. Whitney, in stream (2 ex. FSCA); Rhode Island: Washington Co., Carolina, 24.ix.1970, leg. A. Lavallee (6 ex. FSCA); Kent Co., 1.ix.1969, leg. A. Lavallee (5 ex. FSCA); South Carolina: Aiken Co., Jackson, 4 mi NW at hwy 125 bridge, Holley Creek, 26.iii.1980, leg. D. Huggins, S. Hamilton, SEMC 1054961 (1 ex. KSEM); Tennessee: Cumberland Co., 8 mi S. Crossville, 26.vi.1962, leg. F.N. Young, #1968 (1 ex. FSCA); Maury Co., Colombia (1 ex. MTEC); Virginia: Albemarle Co., Charlottesville, 27.xi.1947, leg. H.H. Hobbs (1 ex. FSCA); West Virginia: Grant Co., 9 mi. SW Petersburg, 2.ix.1973, leg. J.B. Heppner (7 ex. FSCA).

Male (Fig. 14C–D): Size: 10.9–12.1 mm. Body form narrowly oval, attenuated anteriorly; elytral apices rounded with sutural angle produced into a point, rarely with point reduced and elytra appearing completely rounded, apicolateral sinuation present, serrations and/or irregularities absent, elytral striae very faint, most evident medially, elytra with fine microreticulation covering entirety, laterally microreticulation often coarser, medially with fine weakly impressed punctures; profemora with small weakly produced sub-apicoventral tooth; protibia weakly club-shaped, approaching subsinuate in large males, with distolateral margin weakly produced; mesotarsal claw as in Fig. 15C; venter lightly colored red to reddish orange; Aedeagus (Fig. 15A, B, D) median lobe in dorsal view parallel sided basally, weakly constricted medially, weakly narrowed in apical 1/3, apex obtusely rounded, in lateral view median lobe narrowed in apical 1/4, in ventral view sperm-groove parallel sided for near entirety of length, apex broadly rounded, parameres narrow, parallel sided, weakly arced basally to apically, apically very flatly rounded.

Female (Fig. 14A–B): Size: 10.6–12.8 mm. Body form narrowly oval, attenuated anteriorly; elytral apices rounded with sutural angle produced into a point, apicolateral sinuation present, serrations and/or irregularities absent, elytral striae very faint, most evident medially, elytra with fine microreticulation covering entirety, laterally microreticulation often coarser, medially with fine weakly impressed punctures; profemora without sub-apicoventral tooth; protibiae laterally weakly curved, distolateral margin weakly expanded; venter lightly colored, red to yellowish orange.

Figure 14. 

Dineutus discolor. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus D ♂ ventral habitus. All scale bars ≈ 2 mm.

Figure 15. 

Dineutus discolor. A aedeagus dorsal view B aedeagus ventral view C ♂ mesotarsal claws D aedeagus lateral view. Scale bar for C ≈ 0.10 mm all others ≈ 1 mm.

Dineutus discolor is unique among all North American species in the elongate oval and attenuate anteriorly body form, the elytra of both sexes with the apices rounded, with the sutural angle produced to a point with an apicolateral sinuation present, without serrations or irregularities present, a lightly colored venter, and males with the profemora with a small apicoventral tooth, and the form of the aedeagus (Fig. 15A). The species most similar to D. discolor is D. angustus. See the differential diagnosis under D. angustus for separation of the two species.

(Fig. 52D). Extreme southeastern Canada from Ontario to Nova Scotia (Majka and Kenner 2009; Roughley 1991; Webster and DeMerchant 2012), and the eastern half of the United States (Epler 2010; Ferkinhoff and Gunderson 1983; Folkerts 1978; Hilsenhoff 1990; Malcolm 1971; Régimbart 1907; Roberts 1895; Sanderson 1982; Wood 1962), south possibly into Mexico: Durango (Ochs 1949).

Dineutus discolor appears to be strictly lotic, inhabiting streams (Ferkinhoff and Gunderson 1983; Hilsenhoff 1990; Webster and DeMerchant 2012), and it has been suggested that this species prefers clear water (Morrissette 1979). In Quebec D. discolor was found in clear running water and in New Brunswick within embayments and along the margins of rivers (Webster and DeMerchant 2012). In Florida, Young (1954) found D. discolor to be a typical inhabitant of small streams in the uplands, avoiding the more acidic streams as well as the true flatwood streams within the state. Within streams D. discolor swims in the current, moving upstream in quick jerks, allowing individuals to maintain their relative position in the stream among their aggregates, and swim downstream to dive and cling to submerged objects when alarmed (Hatch 1925a). In more swift streams D. discolor is often found in eddies behind objects obstructing the current, such as fallen logs, and may be restricted to these habitats (Kolmes 1983a; Vulinec 1987). Stream dwelling Dineutus species also frequent areas where the current is slowed such as pools and wide meanders, avoiding torrential areas, riffles, and more swift currents (Folkerts and Donavan 1973). Members of D. discolor form rafts in areas of flowing water within the streams, with individuals keeping pace so as to remain in position in the raft, and the raft maintains its relative position within the stream (Brown and Hatch 1929; Hatch 1925a). The first author has collected D. discolor in both small pebble-bottomed forested streams as well as large mud-bottomed rivers in the southeastern United States. Both situations had clear water similar to situations described above and individuals collected from larger streams were found in areas with slowed water.

Dineutus discolor has an extensive range from the northern third of Florida up the Atlantic coast to Canada, and west to Iowa and Minnesota (Fig. 52D). The true extent of the western and southern boundaries of the range of D. discolor seems somewhat uncertain. Ochs (1949) lists a single specimen of D. discolor in his collection as having the label “Mexico, Durango”.

Kolmes (1983b; 1985) discussed the precopulatory behavior of D. discolor describing the interesting “Proleg-up” mate signaling used by females. Kolmes (1983a) also investigated aspects of prey capture within this species.

The larvae of D. discolor have been found under stones within streams with adult D. discolor at a depth of 20 cm to 60 cm in areas where water is flowing, but not so rapidly as to create breaks in its surface such as rapids (Brown and Hatch 1929). Hatch (1927) included D. discolor in a key to gyrinid larvae.

While several North American Dineutus specimens carry type designations by “RP Withington III”, these were never published thus do not consistute viable nomenclatural acts according to Article 11 of The Code (ICZN 1999). Among the material in the MNHN there are 4 other specimens designated by Withington III as paralectotypes, aside from the specimen here designated formally as the lectotype. Brinck also included a lectotype label on this specimen, but similarly, Brinck did not publish a written account of specimens he designated at the MNHN as lectotypes. The specimen selected here as the lectotype (Fig. 51B) has a locality label indicating the specimen is from the U.S. as well as a disc that allows the date and local to be checked in the MNHN’s registrar. Other specimens in the collection (including the unpublished paralectotypes designated by Withington) lack date indications. Therefore only the specimen with the date showing its collection prior to Aubé’s description, and being from the United States (as verified by the registrat at the MNHN) is safe to assume was a part of the original syntype series, and is here formally designated as the lectotype of D. discolor. Given the uncertainty of the other specimens suggested to be paralectotypes by Withington III, it is our opinion that these specimens should not be regarded as paralectotypes.

None given.

75

None examined, none available. The Thomas Say entomology collection is known to have suffered substantial damage with portions of his type collection having been destroyed (Mawdsley 1993). Mawdsley (1993) provided a list of the surviving type specimens, but none of Say’s gyrinid species appear to remain. The MCZ online type database lists the following specimen as being a “Neotype”: (♀, pinned) “340/ ♀/ A. [brown label, handwritten in black ink]// NEOTYPE/ Dineutus emarginatus/ Desig. R.P. Withington III/ 1999 [red label, handwritten in black ink, handwriting unknown]// Dineutus ♀/ emarginatus (Say)/ Det. 1998 1999/ RP Withington III [white label, typed black ink, except cross through 1998, 1999, and female symbol, handwritten in black ink]// emarginatus 5 [white label, handwritten in black ink, unknown handwriting]// MCZ TYPE/ 34947 [red label, MCZ TYPE typed in black ink, 34947 handwritten in black ink]//.” As with all other R.P. Withington III designations for North America Dineutus, they were never published and are invalid, thus this specimen has absolutely no type status. As there is no question as to the identity of Dineutus emarginatus Say, no “exceptional need” exists for the designation of a neotype as per Article 75.3 of The Code (ICZN 1999), and we refrain from designating a neotype.

U.S.A.:Alabama: Monroe Co., 10km W Bowles, 31°33.094'N, 86°59.956'W, 11.v.2006, leg. K.B. Miller (9 ex. MSBA); Connecticut: New London Co., Ledyard, pond, 1.vi.1995, leg. K.B. Miller (2 ex. MSBA); Florida: Alachua Co., 2.ii.1949, leg. S.B. Mansell, (1 ex. FSCA); same as previous except: 23.iii.1949, leg. B.W. Cooper (1 ex. FSCA); same as previous except: 8.iv.1949, leg. E.H. McConkey (1 ex. FSCA); same as previous except: 30.iv.1949, leg. O.S. Russell (1 ex. FSCA); same as previous except: 15.iv.1950, leg. J.T. Darlington, (2 ex. FSCA); Alachua Co., Hatchet Creek, 25.vii.1975, leg. J.B. Heppner (4 ex. FSCA); Alachua Co., Gainesville, 6 mi. SW, 12.iii.1975, leg. L.R. Davis Jr., Blacklight trap (2 ex. FSCA); Clay Co., Camp Blanding Training Site, INSECT SURVEY SITE 11, Sand Pine Scrub, 29°55.599'N, 81°59.914'W, 24.ix.1999, leg. M. & M. Minno, Light trap (1 ex. FSCA); Hernando Co., Weekiwachee Spring, 5.iii.1953, leg. W.C. Sloan (1 ex. FSCA); Highlands Co., Archbold Biol. Sta., 7.iv.1975, leg. L.L. Lampert, UVL (2 ex. FSCA); Highlands Co., Highlands Hammock State. Prk., 11.iv.1964, leg. J. Waters (2 ex. FSCA); Collier Co., Immokalee, 23-28.iii.1960, leg. A.F. Wilson, Blacklight trap (1 ex. FSCA); Liberty Co., Yellow Creek SE of Telogia, 7.x.1992, leg. F.N. Young, #3503 (5 ex. FSCA); Walton Co., Eglin AFB., Range Rd. 205, 4.5 mi W. Hwy-331, 16.vi.1995, leg. P.E. Skelley et al., MV & blacklight (1 ex. FSCA); Georgia: Okefenokee Swamp, 1.iv.1969, leg. T.E. Rogers (1 ex. FSCA); Bibb Co., Macon, 20.v.1969 (1 ex. FSCA); Lowndes Co., 6.v.1963, leg. E.I. Hazard (1 ex. FSCA); Louisiana: West Feliciana, St. Francisville, 17.vi.1955 (1 ex. FSCA); Maryland: Charles Co., Allen’s Fresh, 15.viii.1984, leg. C.L. Staines Jr. (1 ex. FSCA); Prince George’s Co., Blue Pond, 29.ix.1949, leg. H.L. Dozier (1 ex. FSCA); Prince George’s Co., Greenbelt, 4.ix.1954, leg. H.L. Dozier, still pond in woods (1 ex. FSCA); Mississippi: Hancock Co., Turtleskin Creek, 25.iv.1965, leg. R. Hepburn (2 ex. FSCA); New Jersey: Bergen Co., Dumont Woods, 9.iv.1931, leg. C.L. Ragot, (5 ex. FSCA); New York: Queens Co., Corona, Long Island, 16.iv.1927, leg. C.L. Ragot (1 ex. FSCA); North Carolina: Wake Co., Raleigh, Yates Pond, 12.ix.1970, leg. L.L. Lampert (14 ex. FSCA); Ohio: Fairfield Co., Barnebey Center, 31.vii.1978, leg. D. Streett, sweeping net (4 ex. MTEC); Oklahoma: Latimer Co., 3.vii.1987, leg. K.E.M. Galley, at black light (2 ex. FSCA); South Carolina: Aiken Co., Jackson, 4 mi NW at hwy 125 bridge, Holley Creek, 26.iii.1980, leg. D. Huggins, S. Hamilton, SEMC 1054963 (1 ex. KSEM); Texas: Kinney Co., 17m NW Bracktville, 30.x.1997, leg. J.E. Wappes, MV/UV (1 ex. FSCA); La Salle Co., vic. Los Angeles, 11.ix.1993, leg. J.E. Wappes, (1 ex. FSCA); No locality info: “Station”, 8.v.1901, “Hatch Ex.”, (1 ex. MTEC).

Male (Fig. 16C–D): Size: 8.6–11.0 mm. Body form elongate oval; elytral apices regularly broadly rounded, with serrations and irregularities absent apically, elytra with fine reticulation covering its entirety, striae very faintly present, most evident medially on elytral disc, lateral marginal depression of elytra broad, usually extending to lateral elytra apex; profemora with large triangular sub-apicoventral tooth; protibiae subsinuate; mesotarsal claws (Fig. 17C) with ventral margin straight; venter darkly colored, usually black to very dark brown, mesothoracic and metathoracic legs usually lighter in coloration, as well as apex of abdomen; Aedeagus (Fig. 17A, B, D) median lobe in dorsal view shorter than parameres, medially slightly constricted, acuminate in apical 1/5 producing a strong point, apex very shortly rounded, in lateral view median lobe weakly curved dorsally in apical half, ventrally median lobe with large rounded sperm-groove, parameres in dorsal view rounded laterally at apical 1/3, narrowly rounded apically.

Female (Fig. 16A–B): Size: 8.9–10.1 mm. Body form elongate oval; elytral apices regularly broadly rounded, with serrations and irregularities absent apically, apicolateral sinuation usually absent, rarely developed, elytra with fine reticulation covering most of its entirety, striae very faintly present, most evident medially on elytral disc, lateral marginal depression of elytra broad; profemora without sub-apicoventral tooth; protibiae club-shaped; venter darkly colored, usually black to very dark brown, mesothoracic and metathoracic legs usually lighter in coloration, as well as apex of abdomen.

Figure 16. 

Dineutus emarginatus. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus D ♂ ventral habitus. All scale bars ≈ 2 mm.

Figure 17. 

Dineutus emarginatus. A aedeagus dorsal view B aedeagus ventral view C ♂ mesotarsal claws D aedeagus lateral view. Scale bar for C ≈ 0.10 mm all others ≈ 1 mm.

Dineutus emarginatus is unique among all other species of North American Dineutus in being elongate oval in body shape, having the elytral apices broadly rounded, without serrations and/or irregularities present apically, males with profemora possessing a large triangular sub-apicoventral tooth, and the shape of the aedeagus (Fig. 17A). The species most similar to D. emarginatus are D. carolinus and D. solitarius. In general D. emarginatus can be distinguished from D. solitarius in being more elongate oval in body form, as opposed to being more regularly oval. This difference is especially evident in the pronotum. D. emarginatus has the lateral margin of the pronotum more straightly angled posteriorly to anteriorly, while in D. solitarius the pronotal lateral margin is more obtusely angled. The shape of the posterior margin of the pronotum differs between the two species, being more sinuate with the lateral portion of the posterior margin of the pronotum angled towards the posterolateral corners in D. emarginatus as compared to the posterior margin being much more straight and less sinuate in D. solitarius. Dineutus emarginatus in general also has a more evident lateral marginal depression of the elytra compared to D. solitarius.

Males of D. emarginatus have a much larger profemoral sub-apicoventral profemoral tooth than do those of D. solitarius, but the species can be unambiguously separated based on the aedeagus. Both species have the median lobe acuminate, however, the acumination differs between the two species. In D. emarginatus the apex of the median lobe is more rounded (Fig. 17A), with the acumination present as a strong point, whose apex is narrowly rounded. The apex of the median lobe of D. solitarius (Fig. 43A) is narrowed towards the acumination, with the acumination also evenly narrowed and highly pointed, with the apex of the acumination appearing sharp and narrow. In overall appearance the median lobe of D. emarginatus is more broad with a shallow medial constriction giving the basal and apical margins of the aedeagus a more sinuous feel, while in D. solitarius the median lobe is more parallel sided and slightly narrowed apically, becoming slightly broadened just before the acumination.

The females of D. emarginatus are primarily distinguished from females of D. solitarius by the general differences listed for separating the two species.

Dineutus emarginatus can be separated from D. carolinus by the differences listed in the differential diagnosis for D. carolinus.

(Fig. 53D). Most of the eastern half of the United States (Régimbart 1907; Young 1954; Wood 1962; Malcolm 1971; Folkerts 1978; Sanderson 1982).

Dineutus emarginatus can be found in both lotic and lentic habitats (Young 1954). In Florida D. emarginatus is often found at the mouths of slow moving streams or in lakes in regions where wave action is present (Young 1954). This species can also be found in swamp streams, small sand bottomed streams, and canals with running water (Young 1954). The first author has collected this species form a large man-made lake in the Ozarks of Arkansas, as well as in a large slow moving tributary of a mud-bottomed stream (see the discussion under D. amazonicus).

In the past D. emarginatus was divided into two subspecies by Ochs (1929), D. emarginatuss. str. and D. e. floridensis Ochs, 1929. Ochs (1929) based this subspecies on the smaller size of D. e. floridensis from that of the typical form and on the difference in the number of setigerous punctures of the profemora, as well as some minor differences in the body form and elytral shape. This subspecies was also stated to be restricted to peninsular Florida (Ochs 1929; Young 1954) with other populations outside of northern and central Florida being a part of the D. emarginatuss. str. subspecies. Cook et al. (2006) performed a morphometric analysis of several populations of D. emarginatus to assess the claims of a significant difference in size, as that being the main basis for the subspecies D. e. floridensis. Cook et al. (2006) were unable to discriminate between the two subspecies via a morphometric analysis and suggested the synonymy of D. e. floridensis. Ochs (1929) did also mention a difference in the setigerous punctures of the profemora, however as discussed elsewhere, this character is known to be variable.

In a study of gyrinid aggregations at East Texas Primitive Big Thicket by Realza et al. (2007), D. emarginatus was most commonly collected with D. carolinus and also with D. serrulatus analis, but to a lesser extant, but the authors observed that at a given locality both species compositions and proportions were subject to change.

New York.

45

Syntype (♂ pinned, aedeagus extruded) “N.Y./Acc. 4858/Lectotype/ hornii ♂type # 4 C.H.R./LECTOTYPE Dineutus horni Desig: R.P. Withington III 1998/ Dineutus hornii Roberts 1895 Det. L. Cook 2005” AMNH catalog no. 497.

U.S.A.:Iowa: Boone Co., Ledges State Park, 2.v.1955, leg. M.D. Hoffman (2 ex. FSCA); Indiana: Brown Co., nr. Crooked Creek, 1.x.1977, leg. F.N. Young (1 ex. FSCA); Posey Co., Hovey Lake, 17.viii.1965, leg. C.E. White, Blacklight trap (1 ex. FSCA); Massachusetts: Middlesex Co., Hopkinton, 9.v.1915 (1 ex. FSCA); Michigan: Berrien Co., Harbert Dunes, 17.vii.1956, leg. G.H. Nelson, under washup (1 ex. FSCA); Cheboygan Co., 29.vii.1928, leg. F.G. Batcher, (1 ex. KSEM); same as previous except: 25.vii1931, leg. H.B. Hungerford (1 ex. KSEM); Cheboygan Co., Douglas Lake, 29.vii.1927, leg. H.B. Hungerford (1 ex. KSEM); Cheboygan Co., Douglas Lake, Bessey Cr., 30.vi.1925, leg. H.B. Hungerford (1 ex. KSEM); New Hampshire: Carroll Co., “Summer” 1934, leg. N.H. Preble (4 ex. KSEM); New York: Broome Co., nr. Binghamton, 10.vii.1997, leg. K.B. Miller (8 ex. MSBA); Schuyler Co., Texas Hollow State Wildlife Area, 1.ix.1999, leg. K.B. Miller (2 ex. MSBA); Tompkins Co., Ringwood, 42°26'33"N, 76°21'47"W, 20.v.2000, leg. K.B. Miller (7 ex. MSBA); Saint Lawrence Co., Black Lake, 27.vii.1941, leg. E.J. Gerberg (1 ex. FSCA); Westchester Co., White Plains, 14.v.1922, leg. E.H.P. Squire (1 ex. FSCA); same as previous except: 30.v.1923 (1 ex. FSCA);

Putnam Co., Carmel, 2.viii.1923, leg. E.H.P. Squire (2 ex. FSCA); Pennsylvania: Sussex Co., Peck’s Pond, 41°16'55.4"N, 75°15'18"W, 414 m, 29.v.2007, leg. P.A. Lenhart, swimming in pond (2 ex. MSBA); South Carolina: Aiken Co., Jackson, 4 mi NW at hwy 125 bridge, Holley Creek, 25.iii.1980, leg. D. Huggins, S. Hamilton, SEMC 1054964 (1 ex. KSEM); Wisconsin: Richland Co., lower WI River, State Wildlife Area, 2 mi W of Lone Rock, 4.x.1997, leg. A. Ramsdale, on surface of lentic pond, near margin, day (6 ex. MTEC).

Male (Fig. 18C–D): Size: 9.9–10.9 mm. Body form narrowly oval; antennal flagellum short and thick, ultimate segment broad and round; elytral apices rounded, rarely angled toward suture, elytral striae faintly; profemora without sub-apicoventral tooth; protibiae wedge-shaped, with distolateral margin straight; mesotarsal claws (Fig. 19C) similar in size, venter darkly colored reddish brown to black, except epipleura lighter in color, yellow to orange; Aedeagus (Fig. 19A, B, D) median lobe in dorsal view mostly parallel sided, evenly narrowed in apical 1/3, apex strongly narrowed, flatly rounded, in lateral view apex of median lobe weakly curved dorsally; parameres in dorsal view laterally expanded in apical 1/4, nearly evenly rounded apically, in ventral view sperm grove narrow and parallel sided for most its length.

Female (Fig. 18A–B): Size: 10.3–11.3 mm. Body form narrowly oval; antennal flagellum short and thick, ultimate segment broad and round; elytral apices produced, angled towards sutural production, sutural angle produced into a point, apicolateral sinuation present, elytral striae faint basally and laterally, mainly evident apicomedially, becoming more evident apically and laterally; profemora without sub-apicoventral tooth; protibiae laterally weakly curved, distolateral margin weakly expanded; venter darkly colored, reddish brown to black, except epipleura lighter in color, yellow to orange.

Figure 18. 

Dineutus hornii. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus D ♂ ventral habitus. All scale bars ≈ 2 mm.

Figure 19. 

Dineutus hornii. A aedeagus dorsal view B aedeagus ventral view C ♂ mesotarsal claws D aedeagus lateral view. Scale bar for C ≈ 0.10 mm all others ≈ 1 mm.

Dineutus hornii can be distinguished from all other North American species of Dineutus in having the epipleura light yellow to orange, while still having a darkly colored venter (as opposed to similarly lightly colored as in D. discolor) (Fig. 18B, D), and the males by the form of the aedeagus (Fig. 19A). The species most similar to D. hornii are D. assimilis and D. nigrior especially the female forms. But both sexes differ from the following two species in having the epipleura (Fig. 19B, D) lightly colored yellow to orange relative to their darker venters, as well as having antennal flagella that are short and thick with the ultimate segment appearing broad and round. In both D. assimilis and D. nigrior the epipleura is similarly darkly colored like the rest of the venter, and in D. assimilis often accompanied with a metallic sheen. The ultimate segment of the antennal flagellum in both species differs in being angled as opposed to rounded as in D. hornii.

Males of Dineutus hornii can be readily distinguished from both D. assimilis and D. nigrior in having the elytral apices rounded (rarely angled towards the suture) and without the sutural angle produced to a point (Fig. 18C). The aedeagus (Fig. 19A) of D. hornii is more similar to D. nigrior (Fig. 32A), but can distinguished by the median lobe in dorsal view being more parallel sided, being evenly narrowed in the apical 1/3 (as opposed to apical 1/4), and having the apex of the median lobe flatly rounded at the tip. The median lobe also differs from D. nigrior in having the apex weakly curved dorsally in lateral view (Fig. 19D) as opposed to strongly curved in D. nigrior (Fig. 32D). The pararmeres of D. hornii differ from those of D. nigrior in being expanded laterally in the apical 1/4, and evenly rounded apically, and in lateral view being obtusely angled after the basal 1/3 as opposed to strongly angled.

Females of Dineutus hornii can be somewhat fairly easily distinguished from those of D. assimilis and D. nigrior in that the apices of the elytra are angled towards the suture (Fig. 18A) as opposed to being rounded towards the produced sutural angle. This character combined with the epipleural color and the antennal flagellum shape should readily distinguish females of D. hornii from both D. assimilis and D. nigrior.

(Fig. 52B). Extreme southeastern Canada from Saskatchewan to Nova Scotia (Majka 2008; Majka and Kenner 2009; Roughley 1991) and the eastern half of the United States as far south as Texas and northern Florida (Epler 2010; Ferkinhoff and Gunderson 1983; Folkerts 1978; Hilsenhoff 1990; Malcolm 1971; Roberts 1895; Sanderson 1982; Whiteman and Sites 2003; Wood 1962).

This species is primarily lentic and occasionally found in streams (Hilsenhoff 1990; Whiteman and Sites 2003). In Canada D. hornii inhabits boggy and semi-boggy lakes (Morrissette 1979). In the Missouri Prairie Region, Whiteman and Sites (2003) record this species in ponds with Brasneia.

The spelling of the specific epithet hornii is in some places spelled horni, but the discrepancy in spelling was clarified by Majka (2008), finding “horni” to be an incorrect subsequent spelling of hornii. The unambiguously correct spelling is Dineutus hornii (Majka, 2008).

Dineutus hornii forms rafts during the daytime consisting of hundreds to thousands of individuals, which may be composed of multiple species (Heinrich and Vogt 1980). At night some individuals disperse to forage, returning to larger rafts of beetles just before dawn, while others do not leave the larger rafts formed during the day (Heinrich and Vogt 1980), unlike the behavior observed by Fitzgerald (1987) for D. nigrior where the diurnal rafts of this species appeared to totally disperse by night. Heinrich and Vogt (1980) suggest that D. hornii is nocturnal as foraging behavior occurs at night, with the diurnal period spent quiescently in rafts. Brief life history is available in Istock (1966; 1967).

The larva of D. hornii was included in a key to gyrinid larvae by Hatch (1927) and the structure of the egg has been describe by Baker and Wai (1987).

This is a very unique Dineutus species, easily distinguished from all other New World Dineutus, by the elytral apices possessing a spine located between the sutural and apicolateral angles. Serrations and irregularities are also present, and the sutural angle is also produced into a short spine. The venter is usually more lightly colored from reddish to yellow.

This species is endemic to the Caribbean and represents a bit of a population genetics and Caribbean biogeography problem. The species is currently divided into four subspecies, with each island of the Greater Antilles having its own subpsieces, with the two most unique subspecies being found at opposite ends of the species distribution (Cuba and Puerto Rico). The two subspecies occupying the middle area of the range (Jamaica and the Dominican Republic) are less distinct and seem to form a gradient between the morphologies of the two subspecies at the opposite ends. The aedeagi of three of the subspecies are very similar with only that of D. l. portoricensis offering some significant differences. For these reasons we have decided to retain the classification proposed by Ochs (1924, 1926a, 1938) in treating the four forms as subspecies. Future genetic work may shed some light on these issues.

Dineutus longimanus can be distinguished from all other North American species of Dineutus in having the elytral apices spinose with serrations and irregularities present. The subspecies can be separated by the following key:

Cuba, Santiago de Cuba.

17

None examined.

CUBA:Holguín: Sierra de Nipe, 25km S Mayari, Pinares de Mayari, 650 m, 03.vii.1990, leg. M.A. Ivie (7 ex. WIBF); Sierra de Nipe, Rio Piloto, 4.ii.1967, leg. R. Bielawski & A. Riedel (1 ex. WIBF) same as previous except: 590 m, 07.vii.1990, leg. M.A. Ivie (7 ex. WIBF); Pinar del Rio: Sierra del Rosario, Rancho Mundito, 16.vi.1959, leg. M.W. Sanderson, C59-29 (1 ex. FSCA); Sierra del Rosario, ca. 15km S CincoPesos Rangel, 420 m, 29.vi.1990, leg. M.A. Ivie, (1 ex. WIBF).

Male (Fig. 20C–D). Size: 11.4–12.9 mm. Body form regularly elongate oval; elytral apices spinose, with sutural angle produce to a spine, and a second parasutural spine, with thorn-like serrations and irregularities present apically and apicolaterally, apicolateral sinuation mostly absent, elytra with reticulation strong laterally and apically, producing a bronzy appearance, medial disc with reticulation more weakly impressed and composed of smaller cells accompanied by very shallowly impressed punctation, striae mostly effaced by reticulation, if evident at all faintly apparent medially on disc, lateral marginal depression of elytra absent; profemora with very small sub-apicoventral tooth; protibiae club-shaped; mesotarsal claws (Fig. 21C) with ventral margin regularly rounded and evenly narrowed apically; metacoxae with numerous shallow punctures present over most their ventral face; venter lighter in color: reddish brown to reddish orange. Aedeagus (Fig. 21A, B, D) with median lobe in dorsal view shorter than parameres, nearly parallel sided, slightly wider basally and shallowly narrowed apicad, in apical 1/4 shallowly narrowed towards apex, apex regularly rounded, dorsally without narrow carina, ventrally sperm-groove narrow and parallel sided for most its length, apically briefly widened, in lateral view median lobe with dorsal margin shallowly sinuate in apical 1/3, apex broadly rounded; parameres in dorsal view with lateral margins not laterally expanded, parallel sided for most their length, and apically narrowly rounded.

Female (Fig. 20A–B). Size: 10.8–12.4 mm. Body form regularly elongate oval; elytral apices spinose, with sutural angle produce to a spine, and a second parasutural spine, with thorn-like serrations and irregularities present apically and apicolaterally, apicolateral sinuation mostly absent, elytra with reticulation strong laterally and apically, producing a bronzy appearance, medial disc with reticulation more weakly impressed and composed of smaller cells accompanied by very shallowly impressed punctation, striae mostly effaced by reticulation, if evident at all located medially on disc, lateral marginal depression of elytra absent; profemora without sub-apicoventral tooth; protibiae club-shaped; metacoxae with numerous shallow punctures present over most their ventral face; venter lighter in color: reddish brown to reddish orange.

Figure 20. 

Dineutus longimanus cubensis. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus D ♂ ventral habitus. All scale bars ≈ 2 mm.

Figure 21. 

Dineutus longimanus cubensis. A aedeagus dorsal view B aedeagus ventral view C ♂ mesotarsal claws D aedeagus lateral view. Scale bar for C ≈ 0.10 mm all others ≈ 1 mm.

Dineutus longimanus cubensis is unique among the other subspecies of D. longimanus in being smaller in size (10.8–12.9 mm) and having the metacoxae with numerous shallow punctures present and covering most of their surface. The subspecies most similar to D. l. cubensis is D. l. jamaicensis and can primarily be distinguished by the differences in dorsal punctation and the punctures of the metacoxae as provided by the indentification key.

(Fig. 55B). Cuba (Leng and Mutchler 1914a; Ochs 1924, 1926)

Lotic, according to Peck et al. (1998) this subspecies occurs in streams through out Cuba and is an accidental cave inhabitant. Cave records for this species include Cueva Jíbara 8, Santiago de Cuba Province and Cueva Caja de Aqua, Saneti Spiritus Province (Peck et al. 1998).

Information on the subspecies aside from its taxonomy has been scarce. Given what is currently known it appears that D. l. cubensis is only known from Cuba.

It is worth noting that the date of the description of D. l. cubensis is often given as 1926 (Ochs 1929, 1938) as the name was used earlier by Ochs (1926-1927). However, according to Article 12.1 of The Code (ICZN 1999) in order for the nomen to be available it must be accompanied by a description or definition and in 1926 the name was simply used with an asterix making it a nomen nudum at that time. The description of D. l. cubensis was not included until the final part of the work published in 1927 on page 192 (Ochs 1927a). Thus the true date for D. l. cubensis must be 1927 as that is when the nomen satisfied the criteria of The Code for availability.

Blue Mountains, Jamaica, near 4500 ft. MCZ Type No. 23058.

4

Holotype (♂, pinned) “Blue Mts./ nr 4500 ft./ Aug. 13-20 [white label, typed black ink]// Jamaica/ 1934/ Darlington [white label, typed black ink]// 23058/ M.C.Z./ HoloType/ jamaicus/ ochs [red label, 23058, Holo, and jamaicus Ochs, handwritten in black ink, rest typed black ink]// D. longimanus ssp. jamaicus/ Ochs/ 1937/ Type! [white label handwritten in black ink, handwriting appears to be Ochs’]// D. longimanus/ jamaicus/ Ochs/ 1937/ type no. 23058 [white label handwritten in black ink and type no. 23058 in pencil, handwriting appears to be Ochs’]//” deposited in the MCZ.

JAMAICA:St. Andrew Parish: Maryland, Mamme River, 1.viii.1985, leg. M. Barrett, in clear stream (3 ex. FSCA).

Male (Fig. 22C–D). Size: 12.1–13.3 mm. Body form regularly elongate oval; elytral apices spinose, with sutural angle produce to a spine, and a second parasutural spine, with thorn-like serrations and irregularities present apically and apicolaterally, apicolateral sinuation mostly absent, elytra with reticulation strong laterally and apically, producing a bronzy appearance, medial disc with reticulation very weakly impressed and composed of smaller irregularly more transversely shaped cells accompanied by very shallowly impressed punctation, striae mostly effaced by reticulation, if evident at all faintly apparent medially on disc, lateral marginal depression of elytra absent; profemora with very small sub-apicoventral tooth; protibiae club-shaped; mesotarsal claws (Fig. 23C) with ventral margin regularly rounded and evenly narrowed apically; metacoxae with a decent covering of shallow punctures over most their ventral face, laterally only present on posterior half; venter lightly colored: reddish brown to reddish orange. Aedeagus (Figs 23A, B, D) with median lobe in dorsal view shorter than parameres, parallel sided, in apical 1/4 shallowly narrowed towards apex, apex regularly rounded, dorsally without narrow carina, ventrally sperm-groove narrow and parallel sided for most its length, apically briefly widened, in lateral view median lobe with dorsal margin straight, apex broadly rounded; parameres in dorsal view with lateral margins not noticeably laterally expanded, but very weakly sinuate medially, apically narrowly rounded.

Female (Fig. 22A–B). Size: 12.05 mm. Body form regularly elongate oval; elytral apices spinose, with sutural angle produce to a spine, and a second parasutural spine, with thorn-like serrations and irregularities present apically and apicolaterally, apicolateral sinuation mostly absent, elytra with reticulation strong laterally and apically, producing a bronzy appearance, medial disc with reticulation very weakly impressed and composed of smaller irregularly more transversely shaped cells accompanied by very shallowly impressed punctation, striae mostly effaced by reticulation, if evident at all faintly apparent medially on disc, lateral marginal depression of elytra absent; protibiae club-shaped; profemora without sub-apicoventral tooth; metacoxae with a decent covering of shallow punctures over most their ventral face, laterally only present on posterior half; venter lightly colored: reddish brown to reddish orange.

Figure 22. 

Dineutus longimanus jamaicensis. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus D ♂ ventral habitus. All scale bars ≈ 2 mm.

Figure 23. 

Dineutus longimanus jamaicensis. A aedeagus dorsal view B aedeagus ventral view C ♂ mesotarsal claws D aedeagus lateral view. Scale bar for C ≈ 0.10 mm all others ≈ 1 mm.

Dineutus longimanus jamaicensis is unique among the other subspecies of D. longimanus in being larger in size (12.05–13.3 mm) and elongate oval in shape without apicolateral sinuation, and having the metacoxae with numerous shallow punctures covering most of their surface. The subspecies most similar to D. l. jamaicensis is D. l. cubensis and can be distinguished by the differences in dorsal punctation and metacoxal punctation provided in the key.

(Fig. 55B). Jamaica (Leng and Mutchler 1914b; Ochs 1938)

Specimen label data indicate this is a lotic subspecies, with specimens collected from the Mammee river in St. Andrew, Jamaica (FSCA).

Similar to D. l. cubensis not much is known about D. l. jamaicensis aside from its taxonomy. It is currently only known from Jamaica.

Saint-Domingue (= Hispaniola).

25

Gyrinus longimanus Olivier, 1795: lectotype, here designated: (♂ pinned) “MUSEUM PARIS/ I. St. Domingue/ COLL. BOSC 1828 [beige label, typed black ink, except I. St. Domingue handwritten in black ink, handwriting unknown]// G. longimanus/ I. St. Domingue Oliv. [beige label with black border, handwritten in black ink, handwriting appears to be Olivier’s]// TYPE [red label, typed black ink]// LECTOTYPUS/ P. Brinck designavit 1955. [white label, typed black ink]// TYPE [red label, typed black ink]// LECTOTYPE [red label, typed black ink]//” deposited in the MNHN.

DOMINICAN REPUBLIC:Pedernales Prov.: W of Pedernales, on rd to border with Haiti, 18.154° ‘-71.582°, 13.v.2010, leg. G.J. Svenson, sweeping in dry for. & sec. veg. (17 ex. MSBA); N of Pedernales, La Aguita, 18°09.172'N, 71°44.786'W, 188 m, 21.vii.1999, leg. M.A. Ivie, Guerrero, & Dominici (5 ex. WIBF); 1 km N of Banano, Rio Mulitos, 18°09.258'N, 71°45.384'W, 290 m, 17.vi.2005, leg. G. Nearns, (2 ex. FSCA).

Male (Fig. 24C–D). Size: 12.3–13.9 mm. Body form regularly elongate oval, elytra laterally slightly broadened after basal half; elytral apices spinose, with sutural angle produce to a spine, and a second parasutural spine, with small thorn-like serrations and irregularities present apically but greatly reduced apicolaterally, apicolateral sinuation present and shallow, elytra with reticulation strong laterally and apically, producing a bronzy appearance, medial disc with reticulation more weakly impressed and composed of smaller transversely ovoid cells accompanied by shallowly impressed punctation, striae mostly effaced by reticulation, if evident at all faintly apparent medially on disc, lateral marginal depression of elytra shallow; profemora with very small sub-apicoventral tooth; protibiae club-shaped; mesotarsal claws (Fig. 25C) with ventral margin with a well developed denticle; metacoxae with a sparse covering of very shallow punctures over most their ventral face, laterally only present on posterior margin; venter lightly colored: reddish orange to orangey yellow. Aedeagus (Fig. 25A, B, D) with median lobe in dorsal view shorter than parameres, nearly parallel sided, broader basally and weakly narrowed apicad, in apical 1/4 shallowly narrowed towards apex, apex regularly rounded, dorsally without narrow carina, ventrally sperm-groove narrow and parallel sided, in lateral view median lobe with dorsal margin straight, apex angularly rounded; parameres in dorsal view with lateral margins very weakly laterally expanded in apical 1/2, apically broadly rounded.

Female (Fig. 24A–B). Size: 12.3–13.7 mm. Body form regularly elongate oval; elytral apices spinose, with sutural angle produce to a spine, and a second parasutural spine, with small thorn-like serrations and irregularities present apically but greatly reduced apicolaterally, apicolateral sinuation present and shallow, elytra with reticulation strong laterally and apically, producing a bronzy appearance, medial disc with reticulation more weakly impressed and composed of smaller transversely ovoid cells accompanied by very shallowly impressed punctation, striae mostly effaced by reticulation, if evident at all faintly apparent medially on disc, lateral marginal depression of elytra absent; protibiae club-shaped; profemora without sub-apicoventral tooth; metacoxae with a sparse covering of very shallow punctures over most their ventral face, laterally only present on posterior margin; venter lightly colored: reddish orange to orangey yellow.

Figure 24. 

Dineutus longimanus longimanus. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus D ♂ ventral habitus. All scale bars ≈ 2 mm.

Figure 25. 

Dineutus longimanus longimanus. A aedeagus dorsal view B aedeagus ventral view C ♂ mesotarsal claws D aedeagus lateral view. Scale bar for C ≈ 0.10 mm all others ≈ 1 mm.

Dineutus longimanus longimanus is unique among other subspecies of Dineutus longimanus in being elongate oval and broadened posteriorly in the male after basal half of elytra, and having the metacoxae with sparse but present punctation. The subspecies most similar to D. l. longimanus is D. l. portoricensis but can be distinguished from D. l. portoricensis in being smaller in size (12.3–13.9 mm) and the aedeagus lacking a dorsal carina.

(Fig. 55B). Haiti, Dominican Republic, (Leng and Mutchler 1914a; Ochs 1938; Wood 1962)

Lotic species collected in streams throughout the Dominican Republic (M. Fikáček pers. comm.).

Similar to other species not much is known about this species aside from its taxonomy. The extant of range of this and other subspecies of D. longimanus may be obscured due to imprecise identification of subspecies.

Olivier (1795) in his original description of G. longimanus states it is found in St. Domingue and was described from the cabinet of M. Bosc. A single specimen in the MNHN general collection has a label indicating both the aforementioned locality and being from Bosc’s collection, as well as a label in the handwriting of Olivier with the I.D. of G. longimanus, therefore this specimen (Fig. 51E) is here designated as the lectotype for D. longimanus longimanus.

Puerto Rico, Aibonito.

27

Holotype (♂, pinned, aedeagus pointed to specimen) “Aibonito, P. R., June 1-3, 1915/Amer.Mus.Nat.Hist., Dept. Invert. Zool. No. 28073/HOLOTYPE/Dineutus longimanus Oliv. subsp. portoricensis Ochs 1924, Typus ♂” AMNH type catalogue No. 434.

PUERTO RICO: “Hwy-31, Km. 15.4 nr. PasoSecoJct.”, 122 m, 1.viii.1963, leg. P.J. Spangler, (4 ex. WIBF); Germán: Río Cain, at PR361, 1 rd. mi. N jct. PR396, N of San Germán, 18°07.062'N, 67°01.518'W, 103 m, 14.v.2009, leg. C.B. Barr, EMEC 654754, 654755, 654757 (3 ex. EMEC); Lares: Río Camuy, E off PR134 1.2 rd.mi. N jct. PR111, NE of Lares, 18°18.204'N, 66°49.445'W, 278 m, 16.v.2009, leg. W.D. Shepard, EMEC 654756, 654758, 654759, 654760 (4 ex. EMEC); Maunabo: Río Guayanés, at PR181 just S jct. PR182, N Patillas, 18°03.397'N, 65°59.004'W, 422 m, 9.v.2009, leg. C.B. Barr, EMEC 654749-654753 (5 ex. EMEC); San Patillas: trib. Río Grande de Patillas at PR184, Bosque Carite Charco Azul Rec. Center, 18°05.460'N, 66°02.150'W, 597 m, 10.v.2009, leg. C.B. Barr, EMEC 654746-654748 (3 ex. EMEC); Uatado: trib. Río Caonillas E off PR 612, 2.3 rd. mi. N jct. PR140, NE of Utuado, S Lago dos Bocas, 18°18.177'N, 66°38.708'W, 99 m, 17.v.2009, leg. C.B. Barr, EMEC 654738-654745 (8 ex. EMEC).

Male (Fig. 26C–D). Size: 12.3–14.5 mm. Body form regularly elongate oval, elytra laterally slightly broadened after basal half; elytral apices spinose, with sutural angle produce to a spine, and a second parasutural spine, with small thorn-like serrations and irregularities present apically but greatly reduced apicolaterally, apicolateral sinuation present and shallow, elytra with reticulation strong laterally and apically, producing a bronzy appearance, medial disc with reticulation more weakly impressed and composed of smaller transversely ovoid cells along with very shallow punctation, striae mostly effaced by reticulation, if evident at all faintly apparent medially on disc, lateral marginal depression of elytra present and accompanied with a green sheen; profemora with very small sub-apicoventral tooth; protibiae club-shaped; mesotarsal claws (Fig. 27C) with ventral margin with a weak denticle; metacoxae with a sparse covering of very shallow punctures that are almost indistinguishable over most their ventral face, laterally only present on posterior margin; venter lightly colored: reddish orange to yellow-orange. Aedeagus (Fig. 27A, B, D) with median lobe in dorsal view just shorter than parameres, broadest basally, becoming narrowed apicad after basal 1/3, then angularly narrowed again in apical 1/3 toward apex, apex narrowly rounded, dorsally with narrow carina, ventrally sperm-groove narrow and parallel sided, in lateral view median lobe with dorsal margin straight, slightly angled ventrally toward apex, apex broadly rounded; parameres in dorsal view with lateral margins not noticeably laterally expanded, apically broadly rounded.

Female (Fig. 26A–B). Size: 11.2–13.4 mm. Body form regularly elongate oval; elytral apices spinose, with sutural angle produce to a spine, and a second parasutural spine, with small thorn-like serrations and irregularities present apically but greatly reduced apicolaterally, apicolateral sinuation present and shallow, elytra with reticulation strong laterally and apically, producing a bronzy appearance, medial disc with reticulation more weakly impressed and composed of smaller transversely ovoid sculpticells along with very shallowly impressed punctation, striae mostly effaced by reticulation, if evident at all faintly apparent medially on disc, lateral marginal depression of elytra present and accompanied with a green sheen; profemora without sub-apicoventral tooth; protibiae club-shaped; metacoxae with a sparse covering of very shallow punctures that are almost indistinguishable over most their ventral face, laterally only present on posterior margin; venter lightly colored: reddish orange to yellow-orange.

Figure 26. 

Dineutus longimanus portoricensis. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus D ♂ ventral habitus. All scale bars ≈ 2 mm.

Figure 27. 

Dineutus longimanus portoricensis. A aedeagus dorsal view B aedeagus ventral view C ♂ mesotarsal claws D aedeagus lateral view. Scale bar for C ≈ 0.10 mm all others ≈ 1 mm.

Dineutus longimanus portoricensis can easily be distinguished from other subspecies of D. longimanus in being large in size (11.2–14.5 mm), elytral margin with a lateral green sheen, and most distinctly in the form of the aedeagus. The species most similar to D. l. portoricensis is D. l. longimanus but can easily be distinguished from it in being larger in size with the lateral marginal depression having a green sheen, and having the aedeagus with a dorsal carina.

(Fig. 55B). Puerto Rico (Leng and Mutchler 1914b; Ochs 1924).

Few specimens included habitat information. One that did, mentions a roadside stream (WIBF). Historical records also indicate this is a lotic subspecies (Ochs 1924).

Not much is known about this species aside from its taxonomy, and similar to D. l. longimanus the true extant of its range is obscured due to imprecise identification of the subspecies.

Mexico.

44

Holotype (♂ with aedeagus dissected onto card point): “10393” [white label] // “Mexico Schl.” [green label, handwritten in ink, handwriting unknown] // “Hist.-Coll. (Coleoptera)/ Nr. 10393/ Dineutes spec./ Mexico, Schl./ Zool. Mus. Berlin” [green label] // “Din. truncatus/ Sharp/ determ. Ahlwarth” [white label, part handwritten, determination portion typed]// “subspecies/ mexicanus/ Type! Ochs 1924”, [white label, appears to be hand written by Ochs (Horn and Kahle, 1990)]// “subsp. * / mexicanus/ Ochs/ Mexico.” [green label, hand written again by Ochs]// “HOLOTYPUS/ Dineutes truncatus/ ssp. mexicanus Ochs, 1925/ labelled by MNHUB 2012” [red label, typed]// deposited in the ZMHB. Paratypes: (♀ specimen missing left protarsus): “10393” [white label]// “Hits.-Coll. (Coleoptera)/ Nr. 10393/ Dineutes spec./ Mexico, Schl./ Zool. Mus. Berlin” [green label]// “? PARATYPUS/ Dineutes truncatus/ ssp. mexicanus Ochs, 1925/ labelled by MNHUB 2012” [red label]//; (♀ specimen): “4” [white label, handwritten]// “85373” [white label, handwritten]// “Mochtlan/ Guerrero/ Baron” [white label, handwritten]// “Coll./ Harford”, white label “B.C.A. Col. I. 2./ Dineutes/ truncatus,/ Sharp.” [white label, handwritten except for determination]// “Din. truncatus/ Sharp/ determ. Ahlwarth” [red label]// “PARATYPUS/ Dineutes truncatus/ ssp. mexicanus Ochs, 1925/ labelled by MNHUB 2012” [red label]//; (♂ specimen): “Mexico/ J.Flohr G.” [white label]// “94618” [white label, handwritten]// “Hist.-Coll. (Coleoptera)/ Nr. 94618/ Dineutes truncatus Sharp/ Mixco, Juquila, Coll. Flohr/ Zool. Mus. Berlin/” [green label]// “truncatus/ Sh” [white label]// “? PARATYPUS/ Dineutes truncatus/ ssp. mexicanus Ochs, 1925/ labelled by MNHUB 2012” [red label]//; (A single right elytron, glued to card, specimen of unknown sex) “94618” [white label, handwritten]// “Mexico/ J.Flohr G.” [white label, handwritten]// “Hist.-Coll. (Coleoptera)/ Nr. 94618/ Dineutes truncatus Sharp/ Mexico, Juquila, Coll. Flohr/ Zool. Mus. Berlin” [green label]// “? PARATYPUS/ Dineutes truncatus/ ssp. mexicanus Ochs, 1925/ labelled by MNHUB 2012” [red label]//; (♂ specimen headless): “Juquila/ 15” [white label, handwritten]//, “94618” [white label, handwritten]// “Mexico, J.Flohr G.” [green label]// “Hist.-Coll. (Coleoptera)/ Nr. 94618/ Dineutes truncatus Sharp/ Mexico, Juguila, Coll. Flohr/ Zool. Mus. Berlin” [green label]// “PARATYPUS/ Dineutes truncatus/ ssp. mexicanus Ochs, 1925/ labelled by MNHUB 2012” [red label]// (6: ZMHB).

EL SALVADOR: Los Chorros Park, 16.vii.1961 (1 ex. UCRC); Chalatenango: San Jose del Sacare, 15.iii.1927, leg. R.A. Stirton (2 ex. KSEM); Tamanique: 1000 m, 8.xii.1972, leg. S. & L. Steinhauser (5 ex. FSCA); same as previous except: 3.vii.1972, leg. S. & L. Steinhauser (4 ex. FSCA). GUATEMALA:Zacapa: Sierra de los Minas, “El Naranjo”, S slope below San Lorenzo Mine, 15.07329 -89.68481, 1600-1700m, 21-24.v.2010, leg. P. Skelley, oak forest at light (1 ex. FSCA). HONDURAS: “nr Progreso”, Mico Quemado Mts, 6.xii.1958, leg. J.G. Matthysse, (2 ex. MSBA). MEXICO:Guerrero: Malinaltepec, Aserradero, 1500m, 2.xi.2000, leg. F. Pacheco, 24-8 (1 ex. IEXA); México: Villa Guerrero, Porfirio Díaz, Las Puentes, 14.iv.1990, leg. R. Arce, 7-4 (1 ex. IEXA); Michoacán: Chinicuila, Sierra de Coalcomán, La Nuez, Cañada El Colorín, , 15.ix.2003, leg. R. Novelo (2 ex. IEXA); same as previous except:16.ii.2005, leg. Gómex y Novelo, (2 ex. IEXA); Nayarit: 7mi N. Tetitlan, 14.vi.1962, leg. D.H. Janzen, EMEC 204752; 204756; 204853; 204856; 204866; 204894 (6 ex. EMEC); 8 mi SE San Blas, 27.vi.1967, leg. A.R. Hardy, (2 ex. UCRC); Oaxaca: San Juan Bautista Cuicatlán, Río La Concepción, 2.iv.1989 (4 ex. IEXA); km 84 carr 175 Oaxaca-Tuxtepec, 13.vi.1992, leg. R. Novelo (1 ex. IEXA); San José Independencia, Cerro el Vidrio, 1900 m, 25.v.2004, leg. G. Nogueira, (1 ex. IEXA); Veracruz: 6.vii.1965, leg. G.N. Ross, (2 ex. FSCA).

Male (Fig. 28C–D): Size: 14.5–16.8 mm. Body form regularly oval; elytral apices truncate, lateral corner of truncation distinctly angled, serration reduced to small pointed bumps and/or irregularities, apicolateral margin often faintly sinuate, elytral striae visible anteromedially near suture, disappearing laterally and prior to elytral apices, dense microreticulation covering much of elytra and pronotum; ulimate protarsomere (Fig. 30A) less than ca. 2× as long as wide; protibiae club-shaped; profemora with small acute sub-apicoventral tooth; mesotarsal claw (Fig. 29C) with ventral margin with weak denticle; venter darkly colored, usually black to dark reddish brown, mesothoracic and metathoracic legs usually lighter in coloration, as well as apex of abdomen; Aedeagus (Fig. 29A, B, D) with median lobe in dorsal view weakly constricted medially, being roundly expanded in apical 1/3, acuminate in apical 1/5, with apex broadly rounded, in lateral view, apex of median lobe broadly rounded, ventrally median lobe with parallel sided sperm-groove basally, being shortly expanded and rounded apically, parameres very weakly laterally expanded in apical 1/2.

Female (Fig. 28A–B): Size: 13.9–15.9 mm. Body form regularly elongate oval; elytral apices truncate, lateral corner of truncation distinctly angled, serration reduced to small pointed bumps and/or irregularities, apicolateral margin often faintly sinuate, elytral striae often indistinct, visible upon close examination, dense microreticulation covering entirety of elytra and pronotum, giving elytra and the pronotum a polished metal feel; ulimate protarsomere less than ca. 2× as long as wide; protibiae club-shaped; profemora without sub-apicoventral tooth; venter darkly colored, usually black to dark reddish brown, mesothoracic and metathoracic legs usually lighter in coloration, as well as apex of abdomen.

Figure 28. 

Dineutus mexicanus. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus D ♂ ventral habitus. All scale bars ≈ 2 mm.

Figure 29. 

Dineutus mexicanus. A aedeagus dorsal view B aedeagus ventral view C ♂ mesotarsal claws D aedeagus lateral view. Scale bar for C ≈ 0.10 mm all others ≈ 1 mm.

Figure 30. 

♂ protarsus of A D. mexicanus B D. sp. from nr. Tapanatepec, Oaxaca, Mexico C D. truncatus. Scale bar ≈ 1 mm.

Dineutus mexicanus is unique among all other North American Dineutus in having truncate elytra, with the lateral angle distinct, apicolateral sinuation weakly present, blunt serrations and irregularities present apically, males with a small acute profemoral sub-apicoventral tooth, and in the form of the aedeagus (Fig. 29A). The species most similar to D. mexicanus is D. truncatus (of which it used to be considered a subspecies of). The elytral truncature of D. mexicanus differs in form having the apicolateral margin of the eyltra weakly sinuate, the lateral angle distinct, and the striae being more evident than those of D. truncatus, especially in the males. There are also differences in body form discussed in the differential diagnosis section of D. truncatus.

Males of Dineutus mexicanus can further be separated from D. truncatus by the form of the protarsi (Fig. 30A), the mesotarsal claw shape, and the form of the aedeagus. See the differential diagnosis under D. truncatus for details.

For females see the differential diagnosis section for D. truncatus.

(Fig. 54D). From Mexico to El Salvador (Arce-Pérez and Roughley 1999; Ochs 1949).

Unknown. Most specimens observed for this study were old, collected during the late 1950’s to the early 1970’s containing only locality data and lacking habitat data. A single specimen from Guatamela was collected in 2010 with the habitat data given as “oak forest at light” (FSCA).

The elevation of D. mexicanus to full species status was based on the noticeable and significant differences between the aedeagi of D. truncatus and D. mexicanus as well as the external characters discussed in the differential diagnosis section for D. truncatus. These external characters include the protarsi, mesotarsal claws, and the elytral truncature, all found to be reliable indicators of species boundaries in North American Dineutus. The holotype (Fig. 51F) has been examined for this study allowing the characters of D. mexicanus to be unambiguously known and the species status elevation to be embedded securely in accordance with differences found in the type.

The extent of the range of D. mexicanus is currently unclear, due to the unclear identity of historical D. truncatus records. For the current study the eastern most record of D. mexicanus is from the Mico Quemado mountains near Progresso, Yoro, Hondoras (KSEM). Régimbart (1882) mentions a variety of D. truncatus from Honduras, which Ochs (1949) now appears correct in that this record actually refers to D. mexicanus. Specimens of D. mexicanus for this study were also found in El Salvador, from several localities representing the southern-most confirmed record of D. mexicanus. The western-most records for D. mexicanus from this study are from Nayarit, Mexico, 8 miles southeast of San Blas. Confirmed specimens of D. mexicanus are recorded from numerous records between these east and west localities including Guatemala, and the Mexican states of Veracruz, Oaxaca, and Guerrero. It is unclear how far north the range of D. mexicanus extends in Central America and the Isthmus of Tehuanatepec. Based on the limited range data (Fig. 54D), it appears that D. mexicanus may be a mountain endemic, following the Sierra de Madre de Chiapas through Chiapas, Mexico, Guatemala, and into El Salvador and Honduras, going northwest to southeast through its range. Therefore, D. mexicanus may indeed be absent from the Northern Guatemala, Belize, and the Mexican states of Quintana Roo, Yucatan, Campeche, and Tabasco. In the west Dineutus mexicanus records again overlap with mountain ranges, being found in western Oaxaca in the Sierra Madre del Sur, going northwest along the western portion of the Trans-Mexican Volcanic Belt and into the Sierra Madre Occidental, as far north as Nayarit. Ochs (1949) lists a record for Tamaulipas, Mexico near Victoria, possibly for the Sierra Madre Oriental.

USA, Vermont.

34

Syntype (♂ pinned, aedeagus extruded) “Bengtn. Co., Vt./Acc.4858/ LECTOTYPE/ nigrior ♂ type # 1 C.H.R./LECTOTYPE Dineutus nigrior Desig: R.P. Withington III 1998/ Dineutus nigrior Roberts 1895 Det : L. Cook 2005” AMNH type catalogue no. 498.

U.S.A.:Delaware: Sussex Co., Milsboro, 13.v.1973, leg. T.E. Rogers (1 ex. FSCA); Florida: Alachua Co., Gainesville, 27.vi.1961, leg. R.F. Bussey (1 ex. FSCA); Liberty Co., Torreya State Park, 25.v.1981, leg. J.R. Watts, at U.V. (1 ex. FSCA); Indiana: Crawford Co., Grantsburg, 18.vii.1965, leg. D. Eckert, Blacklight trap (1 ex. FSCA); Maryland: Prince George’s Co., College Park, 16.vi.1948, leg. B.K. Detler, in pond (1 ex. FSCA); Prince George’s CO., Blue Pond, 29.ix.1949, leg. H.L. Dozier, (1 ex. FSCA); Massachusetts: Suffolk Co, Forest Hills, 18.iv.1919 (1 ex. FSCA); Michigan: Allegan Co., State Game Area, 17.vii.1986, leg. J.A. Shuey (1 ex. MTEC); Cheboygan Co., Douglas Lake, 30.vii.1927, leg. H.B. Hungerford (1 ex. KSEM); same as previous except: “Mud L”, 31.vii.1923 (1 ex. KSEM); Washtenaw Co., “118 8h”, 24.iv.1921, leg. M.H. Hatch (1 ex. FSCA); Minnesota: Clearwater Co., Elk Springs, Itasca State Park, 12.viii.1965, leg. J.S. Nordin, attracted to U.V. (2 ex. FSCA); same as previous except: 7.vii.1965 (1 ex. FSCA); Morner Co., nr. Grand Meadow, roadside park, 18.viii.1965, leg. R.H. Arnett, in dammed pond (2 ex. FSCA); Missouri: Wayne Co., 3.2 mi WSW of Patterson Co. Rd. 332, deciduous Ozark forest and old field flora, 4.vii.1988, leg. H.M. Webber, at U.V. light (1 ex. FSCA); New Jersey: Cumberland Co., “Dividing Ck. Hansey Creek Rd.”, edge of salt marshes, 30.ix.1989, leg. D. Schloeitzer, at UV light (1 ex. FSCA); New York: Schuyler Co., Texas Hollow State Wildlife Area, 1.ix.1999, leg. K.B. Miller (1 ex. MSBA); Westchester Co., White Plains, 5.ix.1922, leg. E.H.P. Squire (1 ex. FSCA); same as previous except: 3.viii.1923 (2 ex. FSCA); same as previous except: 19.v.1923 (1 ex. FSCA); same as previous except: 30.v.1923 (1 ex. FSCA); same as previous except: 10.iii.1923 (1 ex. FSCA); same as previous except: 18.x.1924 (2 ex. FSCA); same as previous except: 12.iv.1925 (1 ex. FSCA); same as previous except: 19.v.1925 (1 ex. FSCA); Westchester Co., Montrose, 4.vii.1932, leg. C.L. Ragot (1 ex. FSCA); Pennsylvania: Sullivan Co., Picketts Glen St. Pk., 5.vii.1960, leg. G.W. Byers (2 ex. KSEM); Virginia: Giles Co., Mt. Lake Biol. Stat., 30.vi.1968, leg. H. Greenbaum (1 ex. FSCA); Wisconsin: Douglas Co., State Hunting Grounds, “T44N.R12W.Sec.11”, 23.vi.1999, leg. A Ramsdale, black light in barrens (1 ex. MTEC).

Male (Fig. 31C–D): Size: 11.1–11.7 mm. Body form narrowly oval; elytral apices with sutural angle produced into a point, elytral striae faint basally becoming more evident apically and laterally; profemora without a sub-apicoventral tooth; protibiae wedge-shaped, with distolateral margin produced; mesotarsal claws markedly asymmetrical (Fig. 32C), anterior mesotarsal claw larger than posterior claw, venter darkly colored, reddish brown to black with mesothoracic and metathoracic legs lighter in color; Aedeagus (Fig. 32A, B, D) median lobe in dorsal view narrowed in apical 1/4, shortly rounded apically, in lateral view apex of median lobe strongly curved dorsally, parameres strongly curved in lateral view after basal 1/3.

Female (Fig. 31A–B): Size: 11.6–11.7 mm. Body form narrowly oval; elytral apices produced and rounded, with sutural angle produced into a point, apicolateral sinuation strong, elytral striae faint basally, becoming more evident apically and laterally; profemora without sub-apicoventral tooth; protibiae laterally weakly curved, distolateral margin weakly expanded; venter darkly colored, reddish brown to black venter darkly colored, reddish brown to black with mesothoracic and metathoracic legs lighter in color.

Figure 31. 

Dineutus nigrior. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus D ♂ ventral habitus. All scale bars ≈ 2 mm.

Figure 32. 

Dineutus nigrior. A aedeagus dorsal view B aedeagus ventral view C ♂ mesotarsal claws D aedeagus lateral view. Scale bar for C ≈ 0.10 mm all others ≈ 1 mm.

This species is unique among all other species of North American Dineutus in the extremely large size and assymetrical nature of the male mesotarsal claws (Fig. 32C) and the form of male aedeagus (Fig. 32A, B, D). The species most similar to Dineutus nigrior are Dineutus assimilis and Dineutus hornii, of the two the former most closely resembles D. nigrior especially the female members of the species. Females of all three species very closely resemble one another and require careful consideration for identification. Males of the species can be fairly readily distinguished externally, and aedeagal dissections can indisputably separate males of the species.

In general males of D. nigrior can be distinguished from members of D. assimilis and D. hornii by size. Dineutus nigrior males are larger (Size: 11.1–11.7 mm) than males of both D. assimilis and D. hornii. Dineutus nigrior males differ from males of D. hornii in having the sutural angle of the elytral apices produced into a point, and the venter of D. nigrior is much more darkly colored than that of D. hornii, with the epipleura being similarly colored as the thoracic ventrites. Males of D. nigrior can be distinguished from both D. assimilis and D. hornii in having the mesotarsal claws markedly asymmetrical (Fig. 32C) with the anterior tarsal claw being larger than the posterior claw, while in both D. assimilis (Fig. 9C) and in D. hornii (Fig. 19C) the mesotarsal claws are similar in size. The distolateral margin of the protibiae in D. nigrior is produced while in D. assimilis and D. hornii the margin is straight or nearly so. The aedeagus of D. nigrior (Fig. 32A) is most similar to D. hornii (Fig. 19A) but can be distinguished from D. hornii in having the apex of the median lobe strongly curved dorsally in lateral view (Fig. 32D).

The females of D. nigrior are also generally larger (Size: 11.6–11.7 mm) than those of D. assimilis and D. hornii, but unlike the case in the males, females of each of these three species have the sutural angles of the elytra produced into a point. However, the shape of the apices differs between them. In females of D. nigrior the apices of the elytra are regularly rounded, and this situation is most different from D. hornii where the apices are generally angled towards the sutural production. Dineutus nigrior females can be separated from both D. assimilis and from D. hornii in having the distolateral protibial margin produced, similar to the condition in males, but more weakly expanded.

(Fig. 52C). Extreme southeastern Canada from Manitoba to Nova Scotia (Majka 2008; Majka and Kenner 2009; Roughley 1991) and most of the eastern half of the United States as far south as northern Florida (Epler 2010; Folkerts 1978; Gordon and Post 1965; Hilsenhoff 1990; Malcolm 1971; Régimbart 1907; Roberts 1895; Sanderson 1982; Whiteman and Sites 2003; Wood 1962).

Primarily lentic species, found only infrequently in streams (Roberts 1895; Hilsenhoff 1990). In Canada, D. nigrior prefers semi-boggy lakes (Morrissette 1979). In the Missouri Prairie Region, Whiteman and Sites (2003) found this species associated with the plant taxa Brasneia and Lespedeza.

Fitzgerald (1987) described the social system of Dineutus nigrior in detail and Fairn et al. (2008) studied the effects of parasitism by larval water mites of the genus Eylais Latreille, 1796 on adults of Dineutus nigrior. Evidence for sexual selection within this species has also been investigated (Fairn et al. 2007a; Fairn et al. 2007b). Brief life history information is available in Istock (1966; 1967).

Key to the larvae of D. nigrior provided by Hatch (1927).

USA, Texas.

17

Syntype (♂ pinned) “Tex./Acc. 4858/Type productus, ♂type # 2, C.H.R./Dineutus productus Roberts 1895 Det: L. Cook 2005” AMNH type Catologue 496.

U.S.A.:Kansas: Bourbon Co., Ft. Scott, ca. 2 mi NE, Marmaton River, “T25S R25Esec 20 NW 1/4”, 4.viii.1976, leg. S. Hamilton, T. Oldham, SEMC 10549560 (1 ex. KSEM); Elk Co., Elk River at Elk Falls, 37.374416 -96.184123, 278m, 22.vi.2014, leg. C. Maier, C. Faris, S. Baca, G.Gustafson, GTG062214B (5 ex. GTGC), Elk River S. of Longton, 37.36960 -96.078735, 262m, 22.vi.2014, leg. C. Maier, C. Faris, S. Baca, G.Gustafson, GTG062214A (6 ex. GTGC); Greenwood Co., Lapland, 4mi S Fall River, east branch, 13.ix.1974, leg. D. Huggins, SEMC 1054959 (1 ex. KSEM); Lyon Co., Lyon Co.-Greenwood Co. line, Verdigiris River, “T21S R10E sec 36 SE 1/4”, 16.vii.1976, leg. S. Hamilton, SEMC 1054955, SEMC 1054957 (2 ex. KSEM); Morris Co., Council Grove Lake, outflows and groves, 13.vi.1974, leg. T. Edmonds, SEMC 1054958 (1 ex. KSEM); Texas: “Sequin”, 26.vi.1938, leg. D.W. Craik (2 ex. KSEM).

Male (Fig. 33C, D): Size: 9.5–9.6 mm. Body form narrowly elongate oval; elytral apices rounded with sutural angle produced to a point, apicolateral sinuation weakly present, irregularities present apically near sutural production, elytral apices strongly deflexed, reticulation of pronotal and elytral discs strongly impressed, producing a bronzy appearance; elytral striae faintly evident, most evident on the subapicomedial portion of the elytral disc; profemora with a very small sub-apicoventral tooth, accompanied by a series of denticles extending proximad, associated with each posterior setigerous puncture of the profemora; protibiae subsinuate; mesotarsal claws (Fig. 34C) long and of similar size, with ventral margin straight; venter darkly colored, usually black to very dark bronzy-brown, with the tibiae and tarsi of mesothoracic and metathoracic legs usually lighter in coloration, as well as apex of abdomen; Aedeagus (Fig. 34A, B, D) median lobe in dorsal view noticeably shorter than parameres, weakly constricted just apicad to middle, acuminate in apical ca. 1/5, apex of acumination flatly rounded, in lateral view median lobe roundly curved dorsally, in dorsal view parameres sinuate laterally after basal 1/3, in apical 1/3 laterally expanded, apically strongly rounded.

Female (Fig. 33A, B): Size: 9.5–9.9 mm. Body form narrowly elongate oval; elytral apices angled towards very strong sutural production, apicolateral sinuation strongly present and with plica, irregularities present apically near sutural production, elytral apices strongly deflexed, reticulation of pronotal and elytral discs strongly impressed, producing a bronzy appearance; elytral striae faintly evident, most evident on the subapicomedial portion of the elytral disc; profemora without sub-apicoventral tooth; protibiae club shaped, with lateral margin round, weakly expanded apicaly; venter darkly colored, usually black to very dark bronzy-brown, with the tibiae and tarsi of mesothoracic and metathoracic legs usually lighter in coloration, as well as apex of abdomen.

Figure 33. 

Dineutus productus. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus. D ♂ ventral habitus All scale bars ≈ 2 mm.

Figure 34. 

Dineutus productus. A aedeagus dorsal view B aedeagus ventral view C ♂ mesotarsal claws D aedeagus lateral view. Scale bar for C ≈ 0.10 mm all others ≈ 1 mm.

Dineutus productus can be distinguished from all other North American Dineutus in males having the profemora with a small sub-apicoventral tooth, accompanied by a series of denticles that extend proximad, with each denticle being associated with a posterior setigerous puncture of the profemora, elongate mesotarsal claws of equal size, with straight ventral margins (Fig. 34C), and in the form of the aedeagus (Fig. 34A). The species most similar to D. productus is D. serrulatus analis. The nominal subspecies of D. serrulatus serrulatus should not be confused with D. productus in that it has a restricted range in Florida, and its elytral apices would not easy be confused with those of D. productus, being regularly rounded, with a strong apicolateral sinuation in both sexes and the dorsum being polished black in appearance. Dineutus serrulatus analis on the other hand tends to be variable in the appearance of the elytra (Fig. 37A, C), with some members having the sutural angle produced and the dorsum with strong microreticulation giving the elytra and pronotum a polished bronzed appearance, similar in both respects to D. productus.

Dineutus productus can generally be separated from D. serrulatus analis in having a more elongate narrow body form (Fig. 33A, C), and being smaller in size. Dineutus productus is much more narrowly attenuated anteriorly, compared to D. s. analis, which is broader in body form and larger in size. The ventral coloration of D. productus is most often black to very dark brownish red, and frequently accompanied by a bronzy metallic sheen, while the venter of D. s. analis is most often red in color, rarely appearing black and often lacking any metallic sheen. When more darkly colored D. s. analis is much more red in hue, compared to when D. productus is more lightly colored, having a more brownish hue. A few specimens of D. s. analis examined from southeast Kansas had their venters truly black (KSEM) and for these specimens differences between the male secondary sexual characters as well as differences in the elytra allowed for unambiguous identification. The serration of the elytral apices differs between these two species. In D. productus the apices of the elytra only have irregularities present, at most having round bumps that resemble highly reduced serration, while in D. s. analis the serration is present as distinct and fine points.

The males of D. productus can easily be distinguished from those of D. s. analis in that the profemoral sub-apicoventral tooth is small and accompanied by a series of denticles that extend proximad, with each denticle being associated with a posterior setigerous puncture of the profemora, in D. s. analis there is a profemoral sub-apicoventral tooth as normal, but no accompanying series of denticles. This character appears unique to D. productus among all of the North American Dineutus species. The mesotarsal claws also differ greatly between these two species. Dineutus productus males have the mesotarsal claws elongate with their ventral margins straight (Fig. 34C) and lacking a denticle, while in D. s. analis the mesotarsal claws are small, with their ventral margins curved and possessing a denticle (38F). The aedeagus is by far the most definite way to separate the two species. The aedeagus of D. productus (Fig. 34A) has the median lobe shorter than the parameres, and strongly acuminate apically, with the parameres being sinuate after the basal 1/3 and laterally expanded in the apical 1/3, with the apices rounded. In D. s. analis the median lobe (Fig. 38A, D, H) is as long as the parameres, parallel sided for most its length, having only the apical 1/4 narrowed, with the parameres being parallel sided for most of their length, being only weakly expanded in the apical 1/3 and often obliquely truncate, or obliquely flatly rounded.

Females of D. productus (Fig. 33A) can be distinguished from those of D. s. analis in having a much greater apicolateral sinuation of the elytra, the sinuation is so deep that a plica is formed, and the elytral apices have a much steeper angle towards the sutural production than in D. s. analis females (Fig. 37A), which have a much more shallow apicolateral sinuation and more rounded elytral apices. As mentioned earlier the elytra of D. productus have irregularities present apically, but not fine serration, as seen in D. s. analis.

(Fig. 54A). Central and south-central United States (Roberts 1895), into northeastern Mexico (Ochs 1949). As this species is so rarely collected, we list here the states and counties where it has been collected and the identification is not in question: USA:Kansas: Bourbon Co., Elk Co, Greenwood Co., Lyon Co., Morris Co. (this study); Texas: Bosque Co. [Clifton] (Ochs 1929), Brazos Co. [College Station] (Wood 1962), Comal Co. (Wood 1962), Dallas Co. [Dallas County](Ochs 1929), Dimmit Co. (Wood 1962), Karnes Co. [Kenedy](Wood 1962), Neuces Co. [Corpus Christi](Wood 1962); Mexico: Nuevo Leon: Granja Rodriguez on the borders of the Rio Salado alt. 195m (Ochs 1949).

Lotic species, the Kansas Biological Survey field notes (available at the KSEM) indicate the species was collected from slow moving, cool, mud bottomed streams, that were fairly wide. Gustafson et al. (2014) describe the habitat where D. productus was recently collected in detail, accompanied by photos of the habitats. The species has also been taken at light traps placed at water level in the vicinity of rapids, on the borders of the Rio Salado, in Nuevo Leon, Mexico (Ochs 1949).

Dineutus productus appears to be an uncommonly collected species and the reason for this is not exactly clear. Most species found in the United States are uncommon due to a narrow range of endemism (e.g. D. robertsi and D. angustus), but material examined in this study, as well as records from the literature, suggest the range of this species is not as narrow as the previously mentioned species. Dineutus productus was originally described from Texas by Roberts (1895), and most records of this species come from this state (Régimbart 1907; Ochs 1929; Wood 1962). Young (1954) claimed to have specimens from the panhandle of Florida, but Epler (2010) re-examined specimens in the FSCA identified by Young as D. productus, finding them to belong to other species. Hatch (1925a) claimed to have collected the species from the Sangamon River near Decatur, Illinois. Ochs (1949) however, questioned the Illinois record as well as Régimbart’s (1907) from the Carolinas, stating all specimens identified as D. productus from outside of Texas actually belonged to other species upon his examination. In the same paper Ochs (1949) extended the species range southward in to Neuvo Leon, Mexico.

Material examined for this study from Kansas (KSEM, GTGC), was undoubtedly Dineutus productus, confirming that the range of D. productus extends at least that far northward. This adds credence to Hatch’s (1925a) record from Illinois. Furthermore, comparing images of the Sangamon River available online to those provided by Gustafson et al. (2014), they appear to be the same habitat. The first author was unable to locate Régimbart’s specimen of D. productus within the MNHN, in order to confirm Régimbart’s 1907 record, but D. productus was not listed as a species of Dineutus found in North and South Carolina by Sanderson (1982). Given this and the inability to locate the specimen of Régimbart’s from the Carolinas in his collection at the MNHN, we do not treat Régimbart’s 1907 record as a part of the species range. Ochs’ diagnosis of D. productus (1949) matchs our own, therefore we accept his record for the species from Nuevo Leon, Mexico as representing the southern-most extreme for the range. As mentioned above, given the new Kansas records for the species and the habitat photos of the Sangamon River available online, we accept Hatch’s (1925a) record from Illinois, as the northern-most extreme for the species’ range.

Most works treating D. productus only mentioned having examined a few specimens (i.e. small series at most, usually 4 specimens for most studies [Roberts 1895; Régimbart 1907; Ochs 1929, 1949; Young 1954]). Recent collecting revealed that the species could be collected, albeit with much difficulty, which may explain this species rarity in collections (Gustafson et al. 2014). Hopefully accurate information on indentifying this species, as well as modern information of habitat and distribution, will help this species become better known.

U.S.A., Georgia: “West Branch War Woman Creek, Rabun Co., Ga., in the mountains, at an elevation of about 2,000 feet.”.

59

Not examined, but specimens collected from the type locality.

U.S.A.:Georgia: Clayton Co., Warwoman Wldf Mgmt A, Tuckaluge Cr., 34.90155°N 83.30015°W, 533 m, 11.vii.2012, leg. K.B. Miller, KBM11071201 (31 ex. MSBA); Warwoman Cr., 34.89843°N 83.27512°W, 11.vii.2012, leg. K.B. Miller, KBM11071202 (8 ex. MSBA); Cleveland Co., Chattahoochee R., 34.72111°N, 83.74807°W, 12.vii.2012, leg. K.B. Miller, KBM12071202 (11 ex. MSBA); South Carolina: Moutain Rest Co., Sumter Ntl. For., 34.85292°N 83.14336°W, 12.vii.2012, leg. K.B. Miller, KBM11071203 (9 ex. MSBA).

Male (Fig. 35C–D): Size: 12.1–15.5 mm. Body form elongate broadly oval; antennal flagellum narrow and parallel sided, ultimate segment elongate and pointed apically; elytral apices regularly rounded, serration absent, elytra entirely bronzy, elytral striae faint but fairly distinct, 8^th elytral stria with large shallow punctures present; profemora without sub-apicoventral tooth; protibiae club-shaped; anterior mesotarsal claw (Fig. 36C) with strong denticle; venter lightly colored yellow to light orange in coloration; Aedeagus (Fig. 36A, B, D) medial lobe in dorsal view flatly rounded apically, in ventral view sperm-groove triangular, narrowed posteriorly and anteriorly, in lateral view median lobe thick and flat, parameres strongly arced in apical 1/3.

Female (Fig. 35A–B): Size: 13.6–15.1 mm. Body form elongate broadly oval; antennal club narrow and parallel sided, ultimate segment elongate and pointed apically; elytral apices regularly rounded, serration absent, elytra entirely bronzy, elytral striae faint but fairly distinct, 8^th elytral stria with punctures present; profemora without sub-apicoventral tooth; protibiae club-shaped; venter pale yellow in coloration.

Figure 35. 

Dineutus robertsi. A ♀ dorsal habitus B ♀ ventral habitus C ♂ dorsal habitus D ♂ ventral habitus. All scale bars ≈ 2 mm.

Figure 36. 

Dineutus robertsi. A aedeagus dorsal view B aedeagus ventral view C ♂ mesotarsal claws D aedeagus lateral view. Scale bar for C ≈ 0.10 mm all others ≈ 1 mm.

This species is easily distinguished from all other North American species of Dineutus by its large size, profemora lacking a sub-apicoventral tooth, entirely bronzy elytra, and broadly oval body shape with a pale yellow venter. Other North American species with pale venters are much more attenuated in body shape (e.g. Dineutus discolor, Dineutus longimanus).

The species most similar to Dineutus robertsi is D. ciliatus. Dineutus robertsi differs from D. ciliatus in having the antennal club narrow and parallel sided, with the ultimate segment elongate and pointed apically, as opposed to having the flagellum being thicker and rounder with the ultimate segment rounded. Dineutus robertsi also has the 8^th elytral stria with punctures evident laterally as opposed to having them absent or indistinct as in D. ciliatus. The males of D. robertsi can further be distinguished from D. ciliatus in having the anterior mesotarsal claw (Fig. 36C) with a strong denticle. The aedeagus of D. robertsi (Fig. 36A) has the median lobe in dorsal view flatly rounded apically with the apex lacking an apicomedial papilla, as compared to D. ciliatus (Fig. 13A) in which an apicomedial papilla is present. In ventral view (Fig. 36B), the sperm-groove of the median lob is triangular, narrowed posteriorly and anteriorly, as opposed to that of D. ciliatus (13B) which is broader and more parallel sided. In lateral view the median lobe of D. robertsi (Fig. 36D) is thick and flat, not dorsally curved as is the case in D. ciliatus (Fig. 13D). The parameres also differ in being strongly arced in apical 1/3, those of D. ciliatus are weakly arced.

(Fig. 53B). Known from the Appalachian mountains of northeastern Georgia, and southwestern North and South Carolina in the United States (Leng 1911; Sanderson 1982; Wood 1962).

Lotic species, frequenting mountainous streams with rocky bottoms. The second author collected many specimens from moderately high gradient, rocky streams in higher elevation mountainous regions in the southern Appalachians. Specimens were common in pools and margins of the streams. They were not found at lower elevations or on larger rivers where they were replaced by D. discolor and D. ciliatus.

Dineutus robertsi is highly endemic to the Appalachians of northeastern Georgia and southwestertn North and South Carolina (Fig. 53B). For this reason D. robertsi has been infrequently collected and is poorly represented in collections. Once in the range of this species however, it can be regularly collected on mountain streams, and in large numbers. The full extent of the range of D. robertsi is still in question. Further sampling of the Appalachians would be greatly beneficial for determining the extent of the range of this highly endemic species.

Overall this species can be diagnosed in having elytral apices that are serrulate and with apicolateral sinuation present in both sexes, red colored venters, males with a profemoral sub-apicoventral tooth, and in the form of the male aedeagus. A key to the subspecies is provided and each subspecies is treated individually.

This species is wide-ranging, highly variable among populations (Fig. 39), and has been divided into two subspecies: D. serrulatus serrulatus and D. s. analis (Wood 1968). Of these subspecies D. serrulatus serrulatus is more consistent in its characters, while those of D. s. analis are much more variable causing difficulties in separating the two. Dineutus serrulatus analis was originally described as a separate species by Régimbart in 1882, but was relegated to a subspecies of D. serrulatus LeConte by Wood (1968). Recent papers have again treated D. analis as a separate valid species (e.g. Ciegler et al 2003; Realzola et al. 2007). For this study the authors found no single discrete character that could reliably separate the taxa. Although dorsal coloration can usually be used to separate the two subspecies, populations from northern Florida where the two subspecies meet, show intermediate dorsal coloration, being medially polished black, but laterally bronzy green. Furthermore the aedeagi, of the two subspecies are very similar, with only minor differences that appear variable across the entire range of this species. Another useful character for delimiting similar species, the mesotarsal claws, are also similar showing only minor variation. For these reasons we continue to follow Wood (1968) in treating these two taxa as subspecies.