A review of the Neotropical genus Bidessodes Régimbart, 1895 including description of four new species (Coleoptera, Adephaga, Dytiscidae, Hydroporinae, Bidessini)

Abstract The Neotropical genus Bidessodes Régimbart, 1895 is reviewed. Four new species are described, Bidessodes chlorus Miller, sp. n., Bidessodes erythros Miller, sp. n., Bidessodes leukus Miller, sp. n., and Bidessodes melas Miller, sp. n., bringing the total number of species in the genus to 20. A key to species is provided. Important diagnostic features are illustrated and described and distributions of all species based on examined specimens and published records are provided. Recognition of the subgenera of Bidessodes is not justified, and the two names Hughbosdineus Spangler, 1981 syn. n. and Youngulus Spangler, 1981 syn. n., described at the genus rank, are placed in synonymy with Bidessodes.


Introduction
The Neotropical genus Bidessodes Régimbart, 1895 currently includes 16 described species (Nilsson 2016) distributed among three subgenera. Thirteen are in the nominal subgenus with two in B. (Hughbosdinius) Spangler, 1981 and one in B. (Youngulus) Spangler, 1981. Historically, a group of similar looking species of Bidessini in Australia were also placed in this genus, but these were transferred to Neobidessodes Hendrich and Balke thereafter restricting Bidessodes to the New World (Hendrich et al. 2009). Relationships of Bidessodes to other Bidessini genera are not yet clear. The New World Bidessodes were revised by Young (1986).
Within Bidessini, Bidessodes is very similar to Neobidessodes, but Bidessodes have a series of fine denticles along the posterior margins of abdominal ventrites III-V that are absent in Neobidessodes. Several species have conspicuous male dimorphisms, particularly in the meso-and metalegs, prosternum and prosternal process, and last abdominal ventrite. The male genitalia (both the median and lateral lobes) are usually strikingly complex, and the male median lobe is bilaterally symmetrical and deeply bifid.
The first Bidessodes species were described in Bidessus, but most were later described in Bidessodes. Three of these species were described in the genera Youngulus Spangler, 1981 andHughbosdineus Spangler, 1981, based especially on unusual modifications of males (Spangler 1981). These genera were soon placed as subgenera of Bidessodes by Young (1986).
The genus includes a mix of species some of which are relatively abundant and widespread, and others that are rare and restricted in distribution. They occur in shallow lentic and lotic (especially sandy forest stream) habitats.
The purpose of this research is to describe four new species discovered in northern South America as the result of focused collecting in the region. Most Bidessodes species are very distinctive, and new species are relatively easily recognized and diagnosed from others. Because a number of species were described since the last revision (Braga and Ferreira-Jr. 2009) and there have been nomenclatural changes Hendrich et al. 2009), the entire genus is briefly reviewed here.

Material and methods
Measurements. Measurements were made with an ocular scale on a Zeiss Discovery V8 dissecting microscope. The diagnostic range of measurements of structures was emphasized, so the largest and smallest specimens were preferentially measured. Measurements include: 1) total length (TL), 2) greatest width across elytra (EW), 3) greatest width of pronotum (PW), 4) greatest width of head (HW), and 5) distance between Elytra. The coloration of the elytra is variable between species with some nearly immaculate, others vaguely or indistinctly maculate and others more distinctly maculate or longitudinally striate.
Prosternum. The prosternum in some species is medially longitudinally carinate and setose in either just males (B. obscuripennis (Zimmermann, 1921)) or in both males and females (B. knischi (Zimmermann, 1921)). Most species have the prosternum and prosternal process not conspicuously modified. The prosternal process is somewhat variable in shape, however, with lateral margins curved to subparallel and the apex truncate to broadly rounded to pointed or acuminate. The process may be longitudinally grooved, slightly convex or flat.
Metasternum. There is a distinctive transverse impression across the metaventrite in B. knischi. Other species are unmodified.
Legs. The male pro-and mesotarsomeres are generally more or less broadly expanded than those of the female as occurs in most species of Dytiscidae. This is less evident in some species, especially B. subsignatus (Zimmermann, 1921). In some species, the male mesofemur is apically swollen or expanded. In several species, the base of the male mesotibia is distinctly bent (e.g. Fig. 66). A few species have the metatibia and metafemur expanded or otherwise modified in characteristic ways (e.g. Figs 50,81).
Male genitalia. The male genitalia hold the best set of diagnostic features for species identification. The median lobe in all species is bilaterally symmetrical but is highly species-specific in shape. The lateral lobes are bisegmented and bilaterally symmetrical, as are most Bidessini, and their shapes are highly species-specific, similar to the median lobe. Some are quite complex in shape.
Comments. The genera Hughbosdineus and Youngulus were proposed by Spangler (1981) and relegated to subgenera of Bidessodes by Young (1986). It seems clear, though, that the species were placed in their own genera based on unusual apomorphies rather than clear evidence of phylogenetic isolation. Although there has not been a phylogenetic analysis of the group, these two species appear to be well within the general character-based concept of Bidessodes. There is little justification for continued recognition of three subgenera in Bidessodes, so, Hughbosdineus Spangler, 1981 andYoungulus Spangler, 1981 are each placed as junior synonyms of Bidessodes Régimbart, 1895 (new synonymies).

Key to species of Bidessodes
The following key is modified from Young (1986) and Braga and Ferreira-Jr. (2009). Keys to Bidessodes have been historically based on male attributes. This key is similarly limited. Females of many species are extremely similar and cannot be easily distinguished without association with males. Much of the key requires dissection of male genitalia, and even with the key the best diagnostic method is to dissect male genitalia and compare with descriptions and images of them. Bidessodes fragilis is not keyed given ambiguity about its identity and character combination. Abdominal ventrite VI of male deeply impressed on each side, impression medially carinate; pro-and mesotarsomere I of male not laterally expanded, similar to female mesotarsomeres; male median lobe deeply bifid, with each branch with distinctive apical "hooks" in ventral aspect (Fig. 89); size small, length: 2.0 mm (Fig. 87); Brazil and Guyana (Fig. 103)  Diagnosis. This species does not have a carinate prosternum in either male or female. The prosternal process is longitudinally slightly convex and relatively narrow with the lateral margins distinctly convergent to a pointed apex. The male mesotibia is unmodified. The male metatrochanter and metafemur are unmodified (Fig. 5). The male abdominal ventrite VI is unmodified. The male median lobe in lateral aspect is very small basally with the apical portion abruptly bent and broadly expanded with the apex bilobed (Fig. 2). In ventral aspect the median lobe is very broad basally with the lateral margin concave and the apex broad with a deep, narrow medial emargination (Fig. 3). The basal segment of the lateral lobe is elongate and subsinuate (Fig. 4). The apical segment is elongate and obliquely T-shaped with the apical margin broadly emarginate (Fig. 4). Externally, B. chlorus is similar to many other species of Bidessodes with relatively unmodified ventral surfaces and legs in males or females. The main difference between this species and others is the male genitalia. The shape of the male median lobe and lateral lobes as described above (Figs 2-4) are unlike any other species in the genus. The very broad, angled apical section of the median lobe in lateral aspect ( Fig. 2) is particularly unique.
Coloration (Fig. 1). Head and pronotum yellow, posterior margin of pronotum medially brown. Elytron with base color brown to dark brown with diffuse, transverse pale regions anteriorly, medially and at apex (Fig. 1); surface not iridescent. Head appendages, legs and ventral surfaces yellow to yellow-orange.
Male genitalia. Median lobe in lateral aspect short and robust, basal portion small, apical portion robust, strongly angulate medially, apically broad and truncate (Fig. 2); median lobe in ventral aspect broad basally, medially constricted and expanded apically with lateral margins each broadly concave, medially deeply and narrowly emarginate, lateral branches apically rounded with small medially-directed point (Fig. 3); lateral lobe in lateral aspect irregular, basal portion elongate, curved and constricted medially along ventral margin, apical portion broad basally, apically broadly and obliquely Tshaped with lateral apices pointed and truncate apex shallowly and irregularly concave (Fig. 4).
Sexual dimorphism. Male pro-and mesotarsomeres I-III broader than in female with extensive ventral adhesive setae. Male and female otherwise similar.
Variation. Specimens vary in the extent and intensity of coloration on the elytral surface, though all specimens have some degree of maculation.
Etymology. This species is named chlorus, Greek for "pale green" after one of the four horsemen of the apocalypse.
Habitat. The type specimens were collected at a UV light. No other natural history information is known about this species. Diagnosis. This species does not have a carinate prosternum in either male or female. The prosternal process is broadly triangular, slightly convex and apically acuminate. The male mesotibia is unmodified. The male metatrochanter and metafemur are unmodified (Fig. 10) and the male last abdominal ventrite is unmodified. The male median lobe in lateral aspect is broadly lobate basally with the apical portion long, sublinear, moderately broad with somewhat undulate dorsal and ventral margins and of somewhat even width to a rounded apex (Fig. 7). In ventral aspect the median lobe is moderately broad and similar in width to the apex which is divided into two long rami separated by a narrow, deep medial emargination, with the apex of each ramus narrowed to a point (Fig. 8). The basal segment of the lateral lobe is elongate and irregularly shaped (Fig. 9). The apical segment is small with the apex characterized by an anteriorly directed spinous process on the dorsal margin (Fig. 9). Externally, B. erythros is similar to many other species of Bidessodes with relatively unmodified ventral surfaces and legs in males or females. The main difference between this species and others is the male genitalia as described above. The male median lobe and lateral lobes (Figs 7-9) are unlike any other species in the genus.
Coloration (Fig. 6). Head and pronotum yellow-orange, posterior margin of pronotum medially narrowly brown. Elytron with base color dark brown with weakly differentiated, diffuse, transverse pale fasciae anteriorly, medially and at apex, anterior and medial pale regions meeting in longitudinal areas medially (Fig. 6); surface not iridescent. Head appendages, legs and ventral surfaces yellow to yellow-orange.
Sculpture and structure (Fig. 6). Head with dorsal surface smooth and shiny, with extremely fine micropunctures, broadly dispersed. Pronotum (Fig. 6) smooth and shiny with broadly dispersed micropunctures; lateral margins broadly rounded, pronotum broadest medially, slightly constricted at posterior angles, somewhat less in width than greatest width of elytra; basal striae moderately well impressed, extending about 2/5 distance across pronotum. Elytron (Fig. 6) very broadly curved laterally; shiny, finely microreticulate across surface, distinctly punctate. Prosternal process basally broad and posteriorly slightly convergent to broadly pointed apex, lateral margins somewhat straight and convergent; surface approximately flat. Metaventrite process anteriorly produced with weak lateral carinae that do not extend posteriorly; surface of metaventrite smooth and shiny, not carinate or otherwise modified. Metacoxa with lateral portions shiny, not punctate; metacoxal lines elongate, subparallel, apically distinctly convergent; metatrochanter and metafemur relatively unmodified. Abdominal ventrites smooth, impunctate; ventrite VI smooth, evenly convex, apically broadly pointed.
Male genitalia. Median lobe in lateral aspect with elongate, oval basal part, apical portion nearly straight, robust, with lateral margins subparallel to rounded apex (Fig. 7); median lobe in ventral aspect broad, lateral margins weakly sinuate, similar in width throughout, apex bifid, each branch apically broadly pointed and slightly curved inward, emargination V-shaped (Fig. 8); lateral lobe in lateral aspect with basal segment elongate, subtriangular with distict apicoventral lobe at base of apical segment; apical segment short and small, apically with truncate and laterally toothed apex, with large, basally-directed tooth on dorsal margin (Fig. 9).
Sexual dimorphism. Male pro-and mesotarsomes I-III broader than in female and with extensive ventral adhesive setae. Otherwise males and females similar.
Variation. Specimens are relatively consistent in color pattern and other features.
Etymology. This species is named erythros, Greek for "red" after one of the four horsemen of the apocalypse.
Distribution. This species is known only from central Guyana (Fig. 97).
Habitat. The type series was collected from a leaf litter area along the margins of a blackwater creek. Diagnosis. This species does not have a carinate prosternum in either male or female. The prosternal process is broad, broadly convex, with the lateral margins convergent to the rounded apex. The male mesotibia is unmodified. The male metatrochanter and metafemur are unmodified (Fig. 15) and the male abdominal ventrite VI is unmodified. The male median lobe in lateral aspect is very broad basally with the apical portion short and abruptly curved (Fig. 12). In ventral aspect the median lobe is very broad with undulate lateral margins and the apex broad and medially emarginate (Fig.  13). The basal segment of the lateral lobe is short and subquadrate with the proximate margin toothed (Fig. 14). The apical segment is elongate and T-shaped with the apical margin broadly curved and with a series of setae (Fig. 14). Externally, B. leukus is similar to many other species of Bidessodes with relatively unmodified ventral surfaces and legs in males or females. The main difference between this species and others is the unique male genitalia. The male median lobe and lateral lobes (Figs 12-14) are unlike any other species in the genus. In particular, the median lobe is very broad in ventral aspect (Fig. 12) and robust and strongly curved in lateral aspect (Fig. 13).
Coloration (Fig. 11). Head and pronotum yellow, posterior margin of pronotum medially narrowly brown. Elytron with base color brown with very weakly differentiated, diffuse, transverse pale regions anteriorly, medially and at apex (Fig. 11); surface not iridescent. Head appendages, legs and ventral surfaces yellow to yellow-orange.
Sculpture and structure (Fig. 11). Head with dorsal surface smooth and shiny, with extremely fine micropunctures. Pronotum (Fig. 11) smooth and shiny with few broadly dispersed micropunctures; lateral margins broadly rounded, pronotum broadest medially, slightly constricted at posterior angles, about same width as greatest width of elytra; basal striae moderately well impressed, extending to nearly 1/2 distance across pronotum. Elytron (Fig. 11) very broadly curved laterally; shiny, finely microreticulate across surface, impunctate. Prosternal process basally broad and posteriorly slightly convergent to broadly rounded apex, lateral margins broadly rounded; surface approximately flat. Metaventrite process anteriorly produced with weak lateral carinae that do not extend posteriorly; surface of metaventrite smooth and shiny, not carinate or otherwise modified. Metacoxa with lateral portions shiny, not punctate; metacoxal lines elongate, subparallel, apically distinctly convergent. Abdominal ventrites smooth, impunctate; ventrite VI smooth, evenly convex, apically broadly pointed.
Male genitalia. Median lobe in lateral aspect with basal portion broad and irregular, apical portion robust, short, abruptly curved at nearly right angle medially, apically narrowed to elongate pointed apex (Fig. 12); median lobe in ventral aspect very broad, apically with lateral margins broadly expanded into lobes laterally, apex bifid (Fig. 13); lateral lobe in lateral aspect irregular, basal portion broad and short, basally with lobes and teeth, apical portion elongate and T-shaped, apex broadly expanded laterally, apical margin curved (Fig. 14).
Sexual dimorphism. Females not examined, but male pro-and mesotarsomeres I-III laterally expanded with ventral adhesive setae, similar to other Bidessodes species that exhibit this dimorphism.
Variation. Only a single male specimen was examined.
Etymology. This species is named leukus, Greek for "white" after one of the four horsemen of the apocalypse.
Habitat. The type was collected from slow areas along a sandy forest stream with extensive leaf pack. Diagnosis. This species does not have a carinate prosternum in either male or female. The prosternal process is longitudinally slightly convex and relatively narrow with the lateral margins distinctly convergent to a pointed apex. The male mesotibia is unmodified. The male metatrochanter and metafemur are unmodified (Fig. 20) and the male last abdominal ventrite is unmodified. The male median lobe in lateral aspect is very small basally with the apical portion long, slender and evenly curved to a narrowly rounded apex (Fig. 17). In ventral aspect the median lobe is slender basally with the lateral margins expanded apically, divided into two long, slender curved rami that bend medially apically (Fig. 18). The basal segment of the lateral lobe is broadly obliquely triangular (Fig. 19). The apical segment is broad and obliquely subrectangular with the apex obliquely subtruncate (Fig. 19). Externally, B. melas is similar to many other species of Bidessodes with relatively unmodified ventral surfaces and legs in males or females. The main difference between this species and others is the male genitalia. The slender, elongate, longitudinally emarginate male median lobe and broad and uniquely shaped lateral lobes (Figs 17-19) are unlike any other species in the genus. This is also one of the smallest species in the genus.
Male genitalia. Median lobe in lateral aspect with small basal portion, apical portion elongate, slender, broadly and evenly curved to narrowly rounded apex (Fig. 17); median lobe in ventral aspect deeply bifid into two elongate, slender rami, apically pointed and with apices curved towards each other apically (Fig. 18); lateral lobe in lateral aspect very robust, basal and apical portions similar in length and width, apical portion broad, apically truncate and toothed (Fig. 19).
Sexual dimorphism. Male pro-and mesotarsomeres I-III broader than in female with extensive ventral adhesive setae. Male and female otherwise similar.
Variation. Specimens vary in the intensity and extent of elytral maculae which are not strongly evident in any specimens.
Etymology. This species is named melas, Greek for "black" after one of the four horsemen of the apocalypse.
Distribution. This species is known only from southwestern Venezuela (Fig. 98).
Habitat. The type series was collected from leaf pack in slow areas along a sandy forest stream. Young, 1986 Figs 21-25, 99 Bidessodes (Bidessodes) acharistus Young, 1986:217;Biström, 1988:7;Nilsson, 2016:98. Diagnosis. This species does not have a carinate prosternum in either male or female. The prosternal process is flat and parallel-sided with the apex broadly acuminate. The male mesotibia is basally bent. The male metatrochanter and metafemur are broad, the metafemur is apically truncate with a distinct denticle along the ventral margin near the apex of the metatrochanter (Fig. 25). The male abdominal ventrite VI is apically slightly impressed medially. The male median lobe in lateral aspect is moderately broad basally with an elongate, broadly curved, slender apical portion that is medially somewhat expanded (Fig. 22). In ventral aspect the median lobe is slender and deeply bifid with each ramus sinuate and subapically expanded and ending in a single pointed process (Fig. 23). The basal segment of the lateral lobe is short and oblique (Fig. 24). The apical segment is very broad and has a broad dorsal expansion apically (Fig. 24). Specimens are relatively immaculate (Fig. 21).

Bidessodes acharistus
Distribution. Known from few localities in Brazil and Bolivia (Fig. 99). Young, 1986 Figs 26-30, 99 Bidessodes (Bidessodes) charaxinus Young, 1986: 213;Biström, 1988: 7;Nilsson, 2016: 98. Diagnosis. This species does not have a carinate prosternum in either male or female. The prosternal process is impressed longitudinally. The lateral margins are slightly convergent apically to the broadly pointed apex. The male mesotibia is elongate, curved, not basally bent. The male metatrochanter and metafemur are not noticeably modified (Fig. 30). The male abdominal ventrite VI is apically somewhat impressed. The male median lobe in lateral aspect is broad with a broad elongate basal region and an apical region that is broad basally and abruptly tapered to an elongate slender apex with a distinct subapical pointed process representing the apicomedial portion of each ramus (Fig. 27). In ventral aspect the median lobe is complex and deeply bifid with each ramus elongate, broad and apically terminating in two sharply pointed processes, and also with a medial terminal lobe between each lateral ramus (Fig. 28). The basal segment of the lateral lobe is small, irregular, and transverse (Fig. 29). The apical segment is broad and complex, terminating in a broad, transverse structure (Fig. 29). Specimens are relatively large and maculate (Fig. 26). Distribution. Known from northern South America (Venezuela, Suriname, Guyana, French Guiana) south into Brazil (Fig. 99).

Bidessodes demarcoi Braga and Ferreira-Jr., 2009 Figs 31-34, 100
Bidessodes (Bidessodes) demarcoi Braga and Ferreira-Jr., 2009: 46;Nilsson, 2016: 98. Diagnosis. Bidessodes demarcoi does not have a carinate prosternum in males or females. The prosternal process is relatively flat, the lateral margins are slightly convergent to the broadly pointed apex. The male mesotibia is unmodified. The male metatrochanter and metafemur are not modified. The male abdominal ventrite VI is sulcate apically. The male median lobe in lateral aspect is broad and broadly curved throughout its length to a sinuate, apically truncate apical region (Fig. 32). In ventral aspect the median lobe is moderately broad with each lateral margin straight, apically slightly divergent and rounded with medial shallow emargination (Fig. 33). The lateral lobe in lateral aspect is extremely broad with a broadly rounded basal portion and the apical portion smaller, but broadly rounded (Fig. 34). Specimens are maculate on the elytra (Fig. 31).
In ventral aspect it is broad and laterally broadly sinuate with the apex shallowly emarginate with each ramus short and sharply pointed (Fig. 37). The basal segment of the lateral lobe is small and transverse (Fig. 38). The apical segment is formed as a slender stalk basally with a very large, transverse apical lobe that is abruptly curved on the ventral apex (Fig. 39). Specimens are elongate slender with maculate elytra (Fig. 35). Discussion. Sharp (1882) mentioned that this species, "… will no doubt form a distinct genus." That eventually proved to be the case as B. elongatus became the type of Bidessodes.
Distribution. The type locality for this species is somewhat ambiguous. The specimens were evidently collected by Champion, but the localities, "Paso Antonio" and "Tortola" are not easily identified today. In a letter from Champion (http://jameschampion.com/diary-2012/thursday-14th-june-2012-letter-13th-march-1881/) he mentions the "Rio Michotoya," which is more easily located, and the star on the map included here reflects that locality (Fig. 101). Known from Guatemala and Costa Rica (Fig. 101). Young, 1986 Figs 41-45, 102 Bidessodes (Bidessodes) evanidus Young, 1986: 212;Biström, 1988: 7;Nilsson, 2016: 98. Diagnosis. This species does not have a carinate prosternum in either male or female. The prosternal process is flat, the lateral margins are slightly convergent to the apically rounded apex. The male mesotibia is unmodified. The male metafemur and metatrochanter are not noticeably modified (Fig. 45). The male abdominal ventrite VI is apically and laterally somewhat impressed. The male median lobe is basally broad, but apically very slender with an apical broad, denticulate expansion (Fig. 42). In ventral aspect it is deeply bifid with each branch slender and apically irregular, and sharply angulate (Fig. 43). The basal segment of the lateral lobe is moderately small and elongate triangular. The apical segment is broad and extremely irregular with a prominent apical, finger-like lobe (Fig. 44). Specimens are elongate oval with the elytra longitudinally vittate (Fig. 41);

Bidessodes fragilis Régimbart, 1900
Discussion. The holotype is a female (Young 1986). Young (1986) was unable to identify this species, but thought it close to B. semistriatus and B. knischi, but also thought B. acharistus may represent the species.
Distribution. Only known from the type locality in Paraguay (Fig. 103).
Bidessodes franki (Spangler, 1981) Figs 46-50, 98 Youngulus franki Spangler, 1981:71. Bidessodes (Youngulus) franki, Young, 1986: 209;Biström, 1988: 7;Nilsson, 2016: 98. Diagnosis. Males and females do not have a medially modified prosternum. The prosternal process is flat, the lateral margins are convergent to the broadly pointed apex. The male mesotibia is unmodified. Bidessodes franki are unique in having males with an extremely broad metatrochanter and metafemur with a distinctive fringe of setae along their posterior margins (Fig. 50). The male abdominal ventrite VI is apically distinctly impressed, and broadly impressed laterally. The male genitalia are distinctive with the median lobe in ventral aspect deeply bifid with each branch unforked and tapered to a point (Fig. 47). In lateral aspect the median lobe is medially very broad and apically strongly tapered and straight to a sharp apex (Fig. 48). The lateral lobe has a reduced basal segment and the apical segment large and irregularly margined with a distinctive lobe on the apicodorsal margin that is directed basally (Fig. 49). Specimens are robust, relatively large and have maculate elytra (Fig. 46).

Distribution.
Found across northern South America from central Colombia to southern Suriname (Fig. 98). Braga and Ferreira-Jr., 2009 Figs 51-54, 104 Bidessodes (Bidessodes) hamadae Braga and Ferreira-Jr., 2009: 46;Nilsson, 2016: 98. Diagnosis. Specimens do not have modified prosternum. The prosternal process is flat with the lateral margins somewhat convex and the apex acuminate. The male mesotibia is bent basally. The metafemur and metatrochanter are unmodified. The male abdominal ventrite VI is impressed and sulcate apically. The male median lobe in lateral aspect is basally elongate with an elongate dorsally-directed flange, the apical portion is elongate, medially slightly expanded but nearly straight with the apex slightly hooked dorsally (Fig. 52). In ventral aspect the median lobe is broad with the lateral rami moderately broad, divergent basally, apically obliquely truncate with medial shallow emargination between the apices (Fig. 53). The lateral lobe has the apical segment irregular, broad and apically truncate. The basal portion is elongate Y-shaped (Fig. 54). Specimens are elongate-slender and relatively immaculate with an indistinct apical pale spot (Fig. 51).

Bidessodes hamadae
Discussion. Only females were examined for this study and the figures of the male genitalia (Figs 52-54) are redrawn from Braga and Ferreira-Jr. (2009).

Bidessodes hygrobius Young, 1986
Figs 55-60, 100 Bidessodes (Bidessodes) hygrobius Young, 1986: 216;Biström, 1988: 7;Nilsson, 2016: 98. Diagnosis. This species does not have a carinate prosternum in either male or female. The prosternal process is longitudinally approximately flat, the lateral margins are subparallel, the apex is pointed. The male mesotibia and the male metafemur and metatrochanter are not noticeably modified (Fig. 60). The male abdominal ventrite VI is unmodified. The male median lobe is robust in lateral aspect, abruptly curved, apically pointed with a distinct ventral expanded angulation and a subapical projecting lobe with the apex elongate pointed (Fig. 56). In ventral aspect it is similarly robust with sinuate lateral margins (Fig. 57). The basal segment of the lateral lobe is small and irregular (Fig. 58). The apical segment is extremely irregular with a prominent transverse apical lobe which is hooked on the ventral apex (Fig. 59). Specimens are robust with maculate elytra (Fig. 55). Distribution. Known from lowland Venezuela and French Guiana (Fig. 100). Bidessodes (Bidessodes) jucundus Young, 1986: 209;Biström, 1988: 7;Nilsson, 2016: 98. Diagnosis. This species does not have a carinate prosternum in either male or female. The prosternal process is longitudinally slightly impressed, the lateral margins are convergent to the pointed apex. The male mesotibia is basally abruptly curved (Fig. 66). The male metafemur is moderately broad and has a distinct denticle along the ventral margin apically and another near the apex of the trochanter (Fig. 65). Unlike other species, the lateral pronotal margins are not strongly curved (Fig. 61). The male abdominal ventrite VI is unmodified. The male median lobe is deeply bifurcate with each branch narrow and apically broadly expanded and spatulate in ventral aspect (Fig. 63).
In lateral aspect the median lobe is narrow and abruptly and evenly curved (Fig. 62).
The basal segment of the lateral lobe is very slender and small, and the apical segment is large and broadly round (Fig. 64). Distribution. The species is known from Brazil and Bolivia (Fig. 103). Young (1986) mentioned a potential specimen from Panama, but this seems unlikely. (Zimmermann, 1921) Figs 67-71, 104

Bidessodes knischi
Bidessus (Bidessodes) knischi Zimmermann, 1921: 198;Blackwelder, 1944: 76. Bidessodes knischi, Young, 19691986: 209. Hughbosdinius leechi Spangler, 1981synonymy by Young 1986: 206. Bidessodes (Hughbosdinius) knischi, Young, 1986: 209;Biström, 1988: 7;Nilsson, 2016: 98. Diagnosis. This species differs from all other species in having the base of the prosternal process distinctly carinate to tectiform in both sexes. In males the ridge anteriorly is flattened and distinctly setose with those setae anteriorly distinctly forked. This species and B. obscuripennis each have the prosternal process basally carinate, at least in males, but they are otherwise rather different. In B. obscuripennis, only males are carinate. The prosternal process is flat and broad, the lateral margins are slightly convergent to the broadly rounded apex. Males of B. knischi have the metaventrite with a prominent transverse groove. The male mesotibia is unmodified. The male metafemur is very broad and rounded (Fig. 71). The male abdominal ventrite VI is distinctly impressed apically. The male genitalia are distinctive. The median lobe in ventral aspect is apically bifid with each branch obliquely bifurcated (Fig. 69). In lateral aspect the median lobe is broadly curved and apically sharply pointed with a distinct expansion along the ventral margin corresponding with the lateral branch of each bifurcation (Fig. 68). The lateral lobe is extremely broad with the apical segment very large and broadly triangular (Fig. 70). Specimens are large and robust with maculate elytra (Fig. 67). Distribution. The types were collected from Mato Grosso, Brazil with other specimens collected from lowland areas of South America from Venezuela and Guyana south to Bolivia (Fig. 104).

Bidessodes nessimiani Braga and Ferreira-Jr., 2009
Figs 72-76, 102 Bidessodes (Bidessodes) nessimiani Braga and Ferreira-Jr., 2009: 44;Nilsson 2016: 98. Diagnosis. This species lacks modifications to the prosternum and male metathoracic legs. The prosternal process is approximately parallel sided with the apex rounded. The male mesotibia is bent basally. The male metafemur and metatrochanter are unmodified (Fig. 76). The male abdominal ventrite VI is unmodified. The male median lobe in lateral aspect is basally small and subtriangular with the apical portion slender, sublinear, medially and apically recurved (Fig. 73). In ventral aspect the median lobe is broad with the lateral rami extremely slender, apically slender and pointed obliquely with medial broad emargination (Fig. 74). The lateral lobe in lateral aspect is long and complex. The apical portion is broad, apically truncate and variously and broadly lobed on dorsal and ventral margins. The basal portion is slender and elongate sub-triangular (Fig. 75). Specimens are broad with maculate elytra (Fig. 72).
Distribution. Known from north-central Brazil (Fig. 102). ( Diagnosis. The species differs from others in having the prosternal process anteriorly carinate with distinctive setae in males. Females have the prosternal process unmodified. This species and B. knischi each have the prosternal process basally carinate, at least in males, but they are otherwise rather different. The prosternal process is narrow, flat, with the lateral margins slightly convergent to the pointed apex. The metaventrite is not transversely grooved. The male mesotibia is unmodified. The metatrochanter in males is exceptionally large, distinctly offset and prominent apically (Fig. 81). The male abdominal ventrite VI is apically broadly impressed. The male genitalia are also distinctive. In lateral aspect the median lobe is slender and apically abruptly curved (Fig. 78). In ventral aspect the median lobe is deeply bifid, each branch ending in a bifurcation. The medial branch of each bifurcation is sinuate and apically pointed, the lateral branch is broad and apically subtruncate (Fig. 79). The lateral lobe has the apical segment extremely broad and irregularly margined (Fig. 80). Specimens are robust with complex maculae on the elytra (Fig. 77). Distribution. Known from Guyana and western Brazil (Fig. 100).