Moirainpa amazona Erwin, 1984.

Mentum without foveae; eyes reduced and pubescent, with a few large facets; labrum not covering mandibles; foretibia notched apicolaterally; elytron entire, with serrate humeral margin; ARG absent; body subdepressed, pubescent. ABL = 1.0 mm.

Known from várzea white water inundation forests of the upper to middle Amazon River drainage (Erwin 1984).

Blemus aenescens (LeConte, 1848).

Mentum without foveae; labrum bilobed, covering mandibles; head with single pair of supraorbital setae; elytra truncate; terminal abdominal ventrite of both male and female with four long setae, the lateral pair sickle-shaped. ABL = 1.2–3.0 mm.

Often abundant at lights, this speciose and underdescribed genus is known from southern North America to northern South America and the Caribbean (Erwin 1991, Erwin et al. 2002).

Lymnaeum indicum (Motschuslky, 1851).

Mentum without foveae; labrum bilobed, covering mandibles; head with two pairs of supraorbital setae; elytra slightly truncate; terminal abdominal ventrite of male with two long, straight setae, female with four long, straight setae; body densely to sparsely setose.

This Old World genus is adventive in Hawaii and the Caribbean (Erwin et al. 2002).

Costitachys inusitatus Erwin, 1974.

Mentum without foveae; foretibia with apicolateral notch; body subdepressed, flavotestaceous, shiny; head with single pair of supraorbital setae; basal protarsomere of male dilated, medially dentiform; head (3), pronotum (5), and elytron (8) with prominent longitudinal carinae; ABL = 1.7–2.6 mm.

Known from sandy riparian habitats throughout the Amazon basin, from the eastern Andes of Ecuador and Perú to the Atlantic coast of South America (Erwin 1974; Erwin and Kavanaugh 1999, 2007).

Tachyta picipes Kirby, 1837.

Elongate, subdepressed; mentum lacking foveae; dorsal surface (excluding Old World taxa) with coarse, isodiametric microsculpture; prosternum plurisetose; tarsal claws denticulate; basal two protarsomeres of male dilated, medially dentiform; ARG elongate, slightly hooked anteriorly, close and subparallel to lateral margin of elytron. ABL = 1.8–3.3 mm.

Widely distributed from the boreal Nearctic to Central America and the Caribbean, associated with fallen logs (Erwin 1975).

Tachyxysta howdenorum Boyd & Erwin, sp. n.

Pronotum with distinctly inflated basal section separated from pronotal disc by subsulcate transverse impression; basal section interrupted at midpoint by prominent, deep excavation opposite scutellum; overall form robust, convex.

Size. ABL = 2.4–2.5 mm; SBL = 2.5–2.7 mm; TW = 1.15–1.25 mm.

Form. Compact, robust, convex.

Color. Dorsally piceous, unicolorous (Fig. 2I); antennae and legs lighter, rufotestaceous except for darker basal half of coxae; dorsally glabrous and without microsculpture except for labrum.

Head. Two pairs of supraorbital setae within channeled longitudinal frontal furrows; frons not raised between furrows, often with subtle transverse wrinkles (Fig. 3I); mentum without foveae.

Prothorax. Base of pronotum (Fig. 3I) with deep lateral depression near posterior angle; posterior angle of pronotum raised, prominent; basal section of pronotum convex, interrupted by deep medial excavation opposite scutellum; male without dilated basal protarsomere(s); protibia notched apicolaterally (Fig. 2I); tarsal claws simple, not denticulate.

Pterothorax.Elytral margin reflexed; i1 entire, subsulcate or faintly impressed; i2–i7 not visible; i8 striatiopunctate from humerus to Eo5, apically subsulcate (Fig. 4I); recurrent groove elongate, slightly sinuate, subparallel to elytral margin, and recurved anteriorly (Fig. 5I); surface without spots; elytral ombilicate setae 2, 6, and 8 more than twice as long as next longest seta.

Genitalia. male aedeagus robust, elongate, with unequally sized, apically 3- or 4-setose parameres (Fig. 6E).

The Mexican specimens were collected near or in El Ocote Preserve; the Honduran specimen was collected in an area near Comayagua National Park. Based on collection data from a limited number of specimens, T. howdenorum may be restricted to higher altitudes.

Feminine. Derived from Tachys, the nominate genus of the subtribe Tachyina, and the Greek xustos (=“smooth/polished”), in reference to this species’ unmicrosculptured, glabrous dorsal surface and alluding to its general resemblance to some members of the subtribe Xystosomina, particularly those of the genus Erwiniana.

Holotype: male (UASM) with following label data: “MEXICO. Chiapas, / El Aguacero, 16 km / W Ocozocoautla / 680m 5.[?]13.VI.1990 / H. & A. Howden FIT”. Paratypes: 6 (2 male, 4 female) in CNC, FSCA, UASM, from type locality [1♀, UASM], “MEX.,Jnct.Rts. / 190&195,Chis. / VI-6-1969 / J.M.Campbell” [2♂, one with second label, “At Black / Light”, CNC], “HONDURAS / Comayagua Dept. / Rancho Chiquito / Km 64 / 29 May 1964 // Blanton, Broce, / & Woodruff Coll. / Light:UV, trap” [1♀, FSCA], “Jct.Hwys 190-195, / Chis.Mex.VI.6, / 1969 H.F.Howden” [2♀, UASM].

México: Chiapas: El Aguacero.

Size, form, color, head, prothorax, pterothorax, abdomen, genitalia, and distribution as in description of the genus.

The patronym howdenorum honors Henry and Anne Howden, collectors of the holotype. The Howdens collected several examples included in the type series of T. howdenorum two decades apart in different locations.

Despite its superficial resemblance to the genus Xystosomus, T. howdenorum possesses a combination of characters that support its placement among the Tachyina but discourage its membership in any previously described tachyine genus; T. howdenorum has an apicolaterally notched protibia and an apical recurrent groove reminiscent of Tachyta, but lacks the denticulate tarsal claws diagnostic for that genus (Erwin, 1975).

Elaphropus caraboides Motschulsky, 1862.

Mentum lacking foveae; claws simple; prosternum glabrous; elytron with 2 to 8 visible interneurs, complete or not, and variable in form; i8 impressed entirely or effaced at midpoint or visible only near apex; ARG short, straight or medially arcuate or if elongate and parallel to elytral margin, not recurved anteriorly.

Elaphrus quadrisignatus Duftschmidt, 1812.

i8 impressed from base to apex, subparallel to elytral margin, inserted anteriorly between Eo2 and Eo3; humeral series of elytral ombilicate setal insertions asymmetrically distributed, with Eo4 removed from closely grouped Eo1–3 such that d(3,4) > d(1,2) and d(3,4) > d(2,3); ARG short, straight to medially arcuate or elongate, straight, and parallel to elytral margin (E. yunax).

Old World, Australia; adventive in the Americas.

Bembidium incurvum Say, 1834.

i8 visible near base and apex, middle section effaced; humeral series of elytral ombilicate setal insertions asymmetrically distributed, with Eo4 removed from closely grouped Eo1–3 such that d(3,4) > d(1,2) and d(3,4) > d(2,3); ARG short, straight or medially arcuate.

North and Central America, the Caribbean islands.

Elaphropus marchantarius sp. n.

Mentum lacking foveae; elytron (Fig. 5F) with 8 micropunctulate interneurs; elytral humeral margin serrate; basal half of i8 (Fig. 4F) parallel to elytral margin, meeting or nearly reaching humeral series of setal insertions; humeral setae symmetrically distributed; apical half of i8 curvy, abruptly bent around Eo5+6 and Eo7; apical recurrent groove (Fig. 1E) rudimentary, continuous with i3.

Size. ABL = 2.25–2.8 mm; SBL = 2.35–2.9 mm; TW = 0.95–1.15 mm

Form. Elongate, parallel-sided, subdepressed.

Color. Uniformly yellow-brown to flavous.

Microsculpture. Head and anteromedial part of pronotum with coarse, scaly, isodiametric microsculpture; remainder of pronotum and elytron with linear, transverse microsculpture.

Head. Mentum without foveae.

Prothorax. Basal section of pronotum (Fig. 3F) triangular, rugose, with basal transverse impressions not well-defined; pronotum with dark, medial furrow that does not reach anterior margin; pronotal furrow with shallow basal excavation; convergent transverse impressions barely visible along anterior margin of pronotum; basal protarsomere of male with prominent medial dentiform expansion.

Pterothorax. Elytral margin serrate; humeral margin (Fig. 4F) with four symmetrically spaced setal insertions; elytron with 8 micropunctulate interneurs; i4–7 not reaching apex and i4–5 converging apically (Fig. 1E); basal half of i8 parallel to elytral margin, meeting or nearly reaching humeral series of setae; apical half of i8 deeply impressed, abruptly curved around Eo5+6 and Eo7 and somewhat deviated medially from elytral margin; ARG (Fig. 1E) rudimentary, continuous with i3.

Genitalia. Not examined.

Widely distributed in the Amazon basin. Known from several localities along the Rio Negro (S. Venezuela), Rio Solimões (S. Colombia and Pará, Brazil), and their confluence, and the Rio Xingu (NE Mato Grosso, Brazil).

Masculine. Greek noun, ammos (= “sand”), in reference to the habitat and coloration of the known species of this genus, and Tachys, the nominate genus of the subtribe Tachyina.

Though these beetles are tentatively placed within Elaphropus due to the afoveate mentum, their remarkable (though perhaps homoplasious) resemblance to the foveae-bearing species Meotachys (Scolistichus) riparius, calls into question the long-assumed taxonomic value and phylogenetic distribution of this character. These two species have similarly broad, pan-Amazonian, apparently overlapping distributions. Molecular data should help to clarify whether their shared morphologies are due to convergence of separate lineages or the loss or gain of foveae within a lineage.

Holotype: male (NMNH) with following label data: “BRAZIL/AM-(Rio Solimões) / Ilha de Marchantaria / 59°58'W 3°15'S;Várzea / J. Adis leg. 22 I 1982”. Paratypes: 8 (6 male, 2 female) in NMNH, ZSM from “BRAZIL/AM-(Rio Solimões) / Ilha de Marchantaria / 59°58'W 3°15'S;Várzea / J. Adis leg. 1.10.81” [1♂, NMNH], “BRAZIL/AM-(Rio Solimões) / Ilha de Marchantaria / 59°58'W 3°15'S;Várzea / J. Adis leg 20-2.[?] [handwritten] 1989A” // Lago Camaleão: light trap / 3.60 m above ground on / Macrolobium acaciifolium / leg. C Martius/A Rebello” [1♂, NMNH], handwritten label: “Jacareacanga / Para Brasie / XII-1968 / M. Alvarenga” [1♂, NMNH], “VENEZUELA, T.F.Amaz. / San Carlos de Rio / Negro, 23 Jan. 1985 / P. & P. Spangler, / R.Faitoute,W.Steiner” [1♂, NMNH], “LETICIA,Amazonas / Colombia 700 ft. / Feb.23-Mar.2/74 / H. & A. Howden” [2♂, UASM], “BRAZIL/AM-(Rio Solimões) / Ilha de Marchantaria / 59°58'W 3°15'S;Várzea / J. Adis leg. 22.XII 1981[?]” [1♀, NMNH], “Jacaré P.N.Xingu / M.Grosso- Bras. / XI.1961 / leg.M.Alvarenga” [1♀, ZSM].

Brazil: Amazonas: Rio Solimões, Ilha de Marchantaria, 59°58'W 3°15'S.

Size, form, color, microsculpture, head, prothorax, mesothorax, and distribution as in description of the subgenus.

The specific epithet marchantarius is a toponym referring to Ilha de Marchantaria, the collection locality of the majority of type material, located near Manaus, Brazil.

Elaphropus acutifrons sp. n.

Mentum without foveae; head with prominent keel-like frontoclypeal carina; elytral interneurs punctate, incomplete in length, and reduced in number; i8 visible only in apical half, interrupted and reduced.

Size. ABL = 2.15–2.2 mm; SBL = 2.25–2.325; TW = 0.95–1.0 mm.

Form. (Fig. 2G) Oval, compact, somewhat dorsoventrally compressed.

Color. Dark reddish brown, glabrous with some small punctules.

Microsculpture. Apparently absent, but difficult to see due to specimen condition.

Head. Mentum without deep foveae but with very faint, shallow impressions at base; frons (Fig. 3G) without longitudinal furrows but with keel-like medial carina between deep lateral depressions at clypeus; margin above antennal insertion prominent, with deep sinuate groove extending to midpoint of eye; labrum coarsely microsculptured; gula densely pitted.

Prothorax. Pronotum (Fig. 3G) transversely cordiform with sinuate, somewhat reflexed margins; pronotum nearly twice as wide as long at widest point; basal section sculpted with deep longitudinal wrinkles; posterior angles prominent, square, upturned; transverse impression dividing basal section from pronotal disc punctate, interrupted medially by deep, narrow excavation; medial furrow emerging from basal excavation, not reaching anterior margin; anterior transverse impressions lightly impressed, medially convergent; prosternum sulcate, with pair of prominent longitudinal ovoid bumps; procoxae separated by broad, apically rounded prosternal process; protibial apicolateral notch (Fig. 2G) oblique, rounded, not abrupt as is typical across Elaphropus, not bearing spine.

Pterothorax. Mesepisternum neither foveate nor perforate; elytral interneurs 1–2 punctate, with second effaced near apex; i3 only very faintly impressed (Figs 2G, 5G); ARG very short, extending past Ed4; i8 (Fig. 4G) interrupted, partially impressed, just visible near (but not passing through) Eo5 and 6, and between Eo7 and 8; elytron with 9 ombilicate and 4 discal setae; humeral setal insertions widely spaced along basal third of elytral margin.

Genitalia. Not examined.

Known only from the type locality of Santarém, Pará, Brazil.

Masculine. From the Greek adjective ídios (=“self/peculiar”), in reference to its unique combination of characters, and Tachys, the nominate genus of the subtribe Tachyina.

Based on its afoveate mentum and apicolaterally notched protibiae, the only known species of Idiotachys is considered to be part of the greater Elaphropus complex. The overall proportions, reduced and punctate elytral strial interneurs, reduced 8th interneur, and arrangement of humeral elytral ombilicate setae diagnostic for the species described below preclude its placement in any existing Elaphropus subgenus.

These, along with unique external characters, support Idiotachys as a lineage distinct from either Tachyura or Barytachys, the two subgenera it most closely resembles.

Holotype: female (AMNH) with following label data: “Santarem”. Paratypes: 1 female in NMNH, from type locality.

Brazil: Pará, Santarém.

Form, size, color, head, prothorax, pterothorax, and distribution as in description of the subgenus.

Derived from the Latin acutus (=“sharp”) and frons (=“front”), in reference to this species’ distinctive raised frons.

Tachys comptus Andrewes, 1922

Mentum without paired foveae; antennae apically lighter than at base (Fig. 2H); dorsal surface glabrous, without microsculpture; pronotum (Fig. 3H) narrowed at base, with posterior angle approximately square or projecting slightly laterad and produced slightly anterior to base of pronotum; foretibia with apicolateral notch; elytron with two pale maculae; i8 inserted basally into deep pit between Eo2 and Eo3; i8 (if complete) distant from elytral margin at midpoint, or (if interrupted) (Fig. 4H) deeply impressed basally and apically; mesepisternum (Fig. 7A) with one or two deep pits; elytron with 4 or 5 discal setae (if 5, 2 basal setae positioned close together); only i1 and i8 visibly impressed; Eo4 distant from Eo3; ARG short, simple.

Southern Africa, South Asia, and South America.

Holotype: male (NMNH) with following label data: “PERU: LORETO / Pithecia 16May90 / 74°45'W 05°28'S / T.L. Erwin Coll. // At light on Launch / in evening after / sunset’. Paratypes: 12 (4 male, 8 female) in AMNH, CAS, CMNH, MZUSP, NMNH, from “PERU: LORETO 1km SW Boca / del Rio Samira Vigilante Post / No. 1 130m 31 Aug 1991 / 04°40.5'S 074°18.9'W // Treading margins of open / grassy marsh, no water / T.L. Erwin & M.G. Pogue / Lot 73” [1♂, NMNH], “Rio Cauaburi / AM, Brasil / 9.XII.1962 / J.Bechyné col.” [1♂, MZUSP], “COLOMBIA:Amazonas / Leticia, 15-VI-65 / P. R. Craig / and J. Robb” [1♂, CAS] , “PERU: MADRE DE DIOS / Pakitza, Rio Manu / 6&9Feb90 T.L. Erwin / 70°58'W 12°07'S // Treading and / quaking river edge / fine silt/sand, / sparse vegetation” [1♂, 1♀, NMNH], “PERU: MADRE DE DIOS / Pakitza, Varzea / 18&21Feb90 TL Erwin / 70°58'W 12°07'S // In leaf litter on / upper flood margin / of Cocha Chica / Tr. Pacal /57” [1♀, NMNH], “PERU: MADRE DE DIOS / Pakitza, quebrada / 06Feb90 T.L. Erwin / 70°58'W 12°07'S // Under leaves at / edge of stream / behind lab, silt” [1♀, NMNH], PERU: LORETO, San / Regis, Rio Maranon / 73°57'W 04°32'S / 04May90, dusk // river margin, at / light on Launch / T.L. Erwin Coll.” [1♀, NMNH], PERU: Madre de Dios / Rio Tambopata Res. / 30km (air) sw Pto. / Maldonato, 290m / 12°50'S 069°20'W // B.M. 1983-455 / N.E.Stork / 3.x.-15.xi.1983 / riverbank” [1♀, NMNH], “BRASIL:Barra do / Tapirape, Mato Grosso, / I:1-15:1966 / B.Malkin leg.” [1♀, CMNH], ARGENTINA,Tucuman: / 15 Km.N.Tucuman, / Rio Sali. / Dec.30,1971 833 / Lee Herman” [1♀, AMNH], handwritten: “Rep Arg / Tucuman / Ciudad 111-59” [1♀, NMNH].

Perú: Loreto, Pithecia, 74°45'W, 05°28'S.

Mentum without foveae; elytron smooth, with two pale maculae and 5 discal setae, Ed1–3 closely grouped in basal third (Fig. 2H); pronotum (Fig. 3H) narrowed at base; mesepisternum (Fig. 7A) with two deep pits; apical half of antennae (Fig. 2H) lighter than basal half.

Size. ABL = 2.0–2.4 mm; SBL = 2.4–2.7 mm; TW = 1.0–1.2 mm.

Form. (Fig. 2H) Convex, shiny, glabrous; pronotum distinctly narrowed at base.

Microsculpture. Absent except for isodiametrically microsculptured labrum.

Color. Glabrous, rufotestaceous to piceous; elytron with two pale maculae.

Head. Mentum without foveae; frons without longitudinal depressions; frontoclypeal suture with very short lateral subfoveate grooves extending posteriad; apical half of antennae abruptly lighter that basal half, nearly white in many specimens.

Prothorax. Pronotum (Fig. 3H) narrowed at base, margins sinuate; posterior angle approximately square; lateral margin of pronotum narrowly explanate, with flange about 2× wider at midpoint than at base or apex and bordered by lateral groove; lateral groove extending to posterior angle; shallow, transverse basal impressions reduced to a series of several small, shallow punctules; basal two protarsomeres of male dilated, medially dentiform.

Pterothorax. Mesepisternum (Fig. 7A) with two deep, circular pits; elytral interneur 8 (Fig. 4H) very deeply impressed from Eo2–4, completely effaced between Eo4 and Eo5, deeply impressed from Eo5 to apex; dorsal surface glabrous and without microsculpture; elytral margin smooth; elytra apically narrowed after Eo5+6; each elytron with two pale spots; i1 subsulcate, 2–7 only visible as subcuticular dots; elytron with 5 discal setae, Ed1–4 in basal ⅔, Ed5 near tip of ARG (Fig. 2H); humeral setal insertions (Fig. 4H) asymmetrically distributed, with 4th removed from 1–3; elytral ombilicate setae 2, 6, and 8 very long, 2–3× the length of the next longest ombilicate seta; ARG (Fig. 5H) short, shallow, extending just past Ed5.

Genitalia. Not examined.

Known from Perú, Brazil, and Argentina. Widespread and apparently abundant in—though not restricted to—riparian habitats.

Derived from the Latin occidens (=“west”), in reference to the New World precinctiveness of this species. This subgenus was previously only described from the Old World.

Trechus bisulcatus Nicolai, 1822

Large in size (> 4 mm); mentum bearing paired foveae; pronotum quadrate, with square to acute hind angles; base of elytra wider than pronotum; elytra round, convex, with width across elytra conspicuously greatest at midpoint; ARG elongate, straight, very close to and subparallel with lateral margin of elytron.

Palearctic—adventive in North America.

Tachys brevicornis Chaudoir, 1846

Very small (< 2 mm), mentum bearing paired foveae; pronotum convex, posterior angles squarely rounded or slightly obtuse; antennae short, submoniliform; i8 reduced, barely impressed, visible apically; ARG very short.

Old World and Australia, with a single species (P. laeva) in the Americas.

Liotachys antennatus Bates, 1871.

Overall form “ant-like”; antennae lighter apically than at base; pronotum pedunculate, slender at base and lacking produced hind angles; mentum bearing paired foveae; elytron smooth, with only i1 visible (subsulcate); i8 not visible; ARG short and arcuate.

Amazon basin.

Tachysbembix sirena Erwin, 2004.

Mentum bearing paired foveae; anterior tibia with apicolateral notch; dorsal surface dull, with coarse, granulate microsculpture; head and eyes large; head and pronotum subequal in greatest width; pronotum round, subcordiform; pronotal hind angles tiny, laterally produced; i8 slightly bent around Eo5–6; ARG elongate, anterior hook laterally remote from 4^th discal seta. ABL = 3.3–3.9 mm.

Known from shoreline habitats along the Pacific coast of Costa Rica (Erwin 2004) and undescribed species from México to Colombia (Erwin in prep).

Tachys scutellaris Stephens, 1828.

Mentum bearing paired foveae; protibia with apicolateral notch; dorsal surface typically with isodiametric microsculpture; pronotum subquadrate; i8 not markedly diverted around Eo5–6 (Fig. 1B); ARG elongate, hooked anteriorly into or effaced laterad of Ed4 (Fig. 1D).

Typically halophilic (Erwin et al. 2002), cosmopolitan.

Tachys austinicus Casey, 1918.

Mentum bearing paired foveae; protibia with apicolateral notch; dorsal surface typically with transverse linear microsculpture and slight iridescence; pronotum subquadrate; i8 conspicuously bent around Eo5–6 (Fig. 1A); ARG elongate, anteriorly hooked around Ed4 (Fig. 1C) (Erwin et al. 2002).

Diverse habitats, cosmopolitan.

Polyderidius rapoporti Jeannel, 1962 by original designation.

Mentum with paired, circular foveae; head with three pairs of supraorbital setae (Fig. 3B), antennae submoniliform; elytral apices rounded/truncate (Fig. 2B), apical recurrent groove hooked anteriorly (Fig. 4B). Many species have reduced eyes and some are brachypterous.

Size. ABL = 1.0–1.2 mm; SBL = 1.1–1.3 mm; TW = 0.45–0.5 mm.

Form. Minute, delicate, dorsolaterally compressed.

Color. (Fig. 2B) Uniformly flavous, flavous with darker head, or uniformly testaceous.

Microsculpture. Varied, from coarse/scaly/isodiametric to fine/linear/transverse.

Head. Head with three pairs of supraorbital setae (Fig. 3B); mentum with paired circular or oval-shaped foveae, or with pair of shallow impressions; eyes reduced in most members; antennae submoniliform and densely setose; subapical labial palpomere conspicuously large and bulbous.

Prothorax. (Fig. 3B) Basal section of pronotum triangular; posterior angles of pronotum bluntly square to rounded and slightly obtuse; procoxae narrowly separated by apically pointed prosternal process; male without dilated basal protarsomere(s).

Pterothorax. Elytral interneurs (if visible) punctate to striatiopunctate and very faintly impressed; i1 often entire, striatiopunctate; no trace of i8; apical recurrent groove (Fig. 4B) thin, well-impressed, and hooked anteriorly; elytral apex (Fig. 2B) rounded and truncate; flight wing with fringed margin, or reduced to a minute pad.

Abdomen. Terminal ventrite with two (male) or four (female) elongated setae.

Genitalia. See Jeannel 1962.

Known from across South and Central America, México, the southeast United States (Alabama, Mississippi), Hawaii, and islands of the Caribbean (Puerto Rico, Cuba) with the greatest species diversity in the Amazon basin (Adis et al. 1986).

Stigmatachys uvea sp. n.

Mentum bifoveate; antennae submoniliform; eyes reduced; labial subulate palpomere absent or reduced; lateral margin of pronotum sinuate; elytral humerus rounded; elytral interneurs punctate and reduced in number, with punctures becoming irregular near apex; abdominal sclerites densely and irregularly punctate.

Size. ABL = 1.2 mm; SBL = 1.35 mm; TW = 0.6 mm.

Form. (Fig. 2A) Minute, compact, convex.

Color. Reddish brown, with lighter appendages.

Microsculpture. Mostly absent, with local patches of isodiametric microsculpture at base of head and around eyes.

Head. (Fig. 3A) Antennae submoniliform; mentum with shallow foveae; head with two pairs of supraorbital setae; eyes reduced, each with about 12 large facets; frontoclypeal suture with small lateral subfoveate depressions; frons without longitudinal depressions; margin above antennal insertion prominent, with longitudinal bead; small dark puncture between gular sutures; labial palps very small, with subulate palpomere reduced or absent.

Prothorax. (Fig. 3A) Pronotum markedly cordiform; posterior lateral margin slightly crenulate; basal section triangular and shallowly pitted/sculptured; basal transverse impressions and medial furrow sulcate, meeting at a point to form triangular basal section; prosternal process very narrow.

Pterothorax. Mesepisternum without pits or foveae; humeral angles obliquely rounded; elytra oval, convex, each elytron (Fig. 5A) with 9 ombilicate and 4 discal setae and 6 visible punctate interneurs, with punctures scattered near apex; lateral channel lined with evenly spaced punctures; i8 not visible (Fig. 4A); elytral margin serrate; elytral disc with a few short, fine setae between i4 and margin; ARG (Figs 4A, 5A) short and deeply engraved, slightly curved medially near apex, directed toward i3.

Abdomen. Ventrites densely punctate and moderately setose.

Genitalia. Not examined.

Known only from the type locality in Loreto, Perú.

Masculine. Derived from the Greek noun stigma (=“mark” or “puncture”), in reference to the coarsely punctate elytra of the lone representative of this genus, and Tachys, the nominate genus of the subtribe Tachyina.

Holotype: female (NMNH) with following label data: “PERU: Dept. Loreto / Campamento San Jacinto / 2°18.75'S, 75°51.77'W / 6 July 1993, 175-215 m / Richard Leschen #39 / ex. rainforest berlese”. Paratypes: none.

Perú: Loreto: Campamento San Jacinto, 2°18.75'S, 75°51.77'W, 175–215m.

Size, form, color, microsculpture, head, prothorax, pterothorax, abdomen, and distribution as in description of the genus.

Derived from the Latin noun uvea (=“grape”), referring to the ovate shape of the elytra of the holotype in dorsal view.

Tachys rufotestacea Hayward, 1900.

Mentum with paired circular foveae; posterior angles of pronotum square to slightly acute (Fig. 3C); elytral interneurs striatiopunctate to micropunctulate, number visible varied; elytral margin partially to entirely serrate; i8 effaced anteriad of Eo5, separated from elytral margin by Eo5–8 (Fig. 4C); apical recurrent groove slightly arcuate, moderately impressed (Fig. 5C); elytral apex with raised plicate interval between i8 and ARG.

Size. ABL = 1.5–2.4 mm; SBL = 1.6–2.5 mm; TW = 0.6–1.0 mm.

Form. Small to minute, compact to elongate and subdepressed.

Color. Flavotestaceous to rufotestaceous.

Microsculpture. Varied; head and pronotum usually with isodiametric microsculpture; elytra with linear/transverse microsculpture or (rarely) glabrous.

Head. Mentum bifoveate; head with two pairs of supraorbital setae.

Prothorax. (Fig. 3C) Pronotum with prominent, square to slightly acute posterior angles; basal section of pronotum triangular, with straight or curved transverse impressions meeting at base of median furrow; basal protarsomere of male dilated, medially dentiform.

Pterothorax. (Fig. 5C) Elytron with one or more striatiopunctate to micropunctulate interneurs; Eo1 at sharpest point of humeral angle; i8 (Fig. 4C) effaced anteriad of Eo5, medially curved and moderately impressed near apex, separated from margin by Eo5–8; elytral margin partially to entirely serrate, serrations inconspicuous to prominent and individually setigerous; apical recurrent groove slightly arcuate, moderately impressed, continuous with or directed toward i3; elytral apex with raised interval between i8 and ARG.

Genitalia. (Based on male genitalia dissected and examined from single individuals of four different species) Male (Fig. 6B, C, F): overall form varied, median lobe with comb-like internal sclerites; both right and left parameres wedge-shaped, stout at base; left paramere large and broad with dark, sclerotized basal hook and 5 apical setae; right paramere smaller, with 4 or 5 apical setae. Female genitalia not examined.

Known from North, Central, and Amazonian South America.

Feminine. Greek adjective nothos (=“false/spurious”), in reference to this diverse and New World-restricted group’s misleading taxonomic history, and deris (=“fight” (Bousquet 2012)), from the name Polyderis. Members of this genus were previously classified within Polyderis based on a lack of useful and distinctive characters owing to their diminutive size; species of Nothoderis are restricted to the New World and are morphologically distinct from Polyderis (an old world genus with one species, P. laeva, widely distributed in North America).

Species of Nothoderis are united by the shape of the pronotum, course of the eighth elytral interneur, features of male genitalia, form of the elytral apical recurrent groove, and preliminary molecular evidence. Male genitalia of Polyderis laeva were also examined and illustrated, and differ notably from all examples of Nothoderis in the form of the internal sclerite(s) and parameres (Fig. 6D). Polyderis laeva remains the sole new world representative of Polyderis s.str. based on external morphology; in addition, preliminary molecular evidence suggests that P. laeva belongs to a lineage phylogenetically distinct from that of N. rufotestacea and other representatives of Nothoderis. Rather, members of this gen. n. are affiliated with the Meotachys/Pericompsus complex (Maddison et al. in prep.).

Tachys ampicollis Bates, 1882.

Subdepressed to dorsally convex; testaceous to rufous; mentum bearing paired circular foveae; foretibia notched apicolaterally; basal protarsomere of male dilated, medially dentiform; mesepisternum with or without small fovea; elytral strial interneurs varied in form, punctate to striatiopunctate; i8 apically curvy, diverted medially at Eo5–6 and Eo7; ARG short and arcuate or rudimentary and continuous with i3. ABL = 1.2–4.6 mm.

Meotachys species occupy diverse habitats and are described from México to southern Brazil (Erwin 1974, 1991).

Meotachys riparius sp. n.

Pronotum and elytra with fine, linear, transverse microsculpture; pronotum quadrate; mesepisternum without fovea(e); elytron with smooth margin and 8 micropunctulate interneurs, 4–7 not extended to apex; apical recurrent groove rudimentary, continuous with i3.

Size. ABL = 2.3–2.35; SBL = 2.475–2.55; TW = 1.05–1.075 mm.

Form. Elongate, subdepressed.

Color. (Fig. 2D) Dark rufous to piceous or bicolored, with head and pronotum lighter.

Microsculpture. Microsculpture of anterior part of head coarse, scaly, isodiametric; pronotal and elytral microsculpture transverse, linear; elytral surface with slight iridescence.

Head. Mentum bifoveate; frontoclypeal suture very faint, with shallow lateral impressions.

Prothorax. (Fig. 3D) Pronotum quadrate; basal section triangular, posterior margin with short rugae; basal transverse impressions well-defined, punctate, interrupted by shallow basal excavation; thin medial furrow emerging from basal excavation not reaching anterior margin of pronotum; anterior convergent impressions short, thin, effaced medially; basal protarsomere of male with prominent dentiform medial expansion.

Pterothorax. Elytral margins smooth; elytron (Fig. 5D) with 8 micropunctulate interneurs; i4–7 not reaching apex; i8 (Fig. 4D) curvy and deeply impressed in apical half, abruptly bent around Eo5+6 and Eo7; ARG (see Fig. 1E) rudimentary, continuous with i3; elytral apex with raised interval between i8 and ARG.

Genitalia. Not examined.

Known from localities across the Amazon basin, from the upper Rio Negro system to the Rio Napo in Ecuador and northeastern Perú, and the lower Solimões River near Manaus.

Masculine. From the Greek skolios (=“crooked”), and stíchos (=“line”/“row”), in reference to the diagnostic curved 8^th interneur.

Holotype: male (UASM) with following label data: “LETICIA, Amazonas / Colombia 700 ft. / Feb.23-Mar.2/74 / H. & A. Howden”. Paratypes: 5 (1 male, 4 female) in NMNH, UASM, from same locality as holotype [1♀, UASM], “BRASIL Amazonas / Rio Demiti, ca. / 0°37'N 66°48'W / below “Highland / Camp” varzea for. / Sept. 11, 1978 // BRASIL EXP. / 1978 / G.E.& K.E. Ball / Collectors” [1♂, UASM], “BRASIL Amazonas / Rio Demiti, near / Little Homestead / 0°35'N 66°41'W / varzea for. Loc. 1 / Sept. 4, 1978 // BRASIL EXP. / 1978 / G.E.& K.E. Ball / Collectors” [1♀, UASM], BRASIL/AM-(Rio Solimões) / Ilha de Marchantaria / 59°58'W 3°15'S;Várzea / J. Adis leg 13-17.5 [handwritten] 1991 // Lago Camaleão: light trap / 3.60 m above ground on / Macrolobium acaciifolium / leg. C Martius/A Rebello” [1♀, NMNH], “ECUADOR Napo Prov. / Laguna Jatuncocha / 20 km s Nuevo Roca- / fuerte on Rio Yasuni / sweep, 8.II.1986 / A.T. Finnamore” [1♀, UASM].

Colombia: Amazonas: Leticia, 700 ft.

Form, color, head, prothorax, mesothorax, and abdomen as in description of the subgenus.

Derived from Latin ripa (=“river bank/edge”), in reference to the riparian habitats throughout the Amazon basin from which this species is known.

Meotachys ballorum sp. n.

Mentum bifoveate, antennae long and slender, pronotal margins sinuate, mesepisternum with single small, deep, reniform pit (Fig. 7B), i1 deeply impressed at base, apical recurrent groove (Fig. 5E) short, faintly impressed.

Size. ABL = 2.7–3.3 mm; SBL = 2.8–3.4 mm; TW = 1.2–1.5 mm.

Form. (Fig. 2E) Elongate, elytra subdepressed to convex.

Color. Matte and dark brown to piceous or glabrous and dark red-brown.

Microsculpture. Varied.

Head. Mentum bifoveate; antennae long, about 2/3 ABL; frons (Fig. 3E) with shallow lateral depressions at clypeus extending posteriad; margin above antennal insertion with shallow groove/channel.

Prothorax. Pronotum (Fig. 3E) transversely quadrate or narrowed near base, with base and apex about equal in width, but greatest width about 1.5× as wide as narrowest width; lateral margin of pronotum markedly sinuate; anterior convergent impressions boldly impressed, not reaching medial furrow; basal transverse impressions deeply punctate, interrupted by small but deep medial excavation; basal section of pronotum opposite scutellum smooth, inflated; thin, medial furrow emerging from basal excavation not meeting anterior margin of pronotum; prosternum smooth, not sulcate.

Pterothorax. Mesepisternum with single, small, reniform pit/fovea, with opening directed slightly posteriad (Fig. 7B); elytron (Fig. 5E) with 3–6 striate interneurs; i1 complete (reaching apex), subsulcate, originating near apex of scutellum, deeply impressed at base; i3–7 incomplete or absent, i3 abruptly bent around Ed2 and Ed3; i5 (either visible as strial interneur or shallow depression) originating at tip of elytral basal margin and clearly separating elytral disc from humeral region; i8 (Fig. 4E) basally effaced and separated from margin by Eo5–8; apical recurrent groove simple, short, faintly impressed.

Known from the type locality in Ecuador, as well as 4 localities along the Rio Negro, northern Amazonas, Brazil, and southern Perú.

Masculine. From the Greek hyle (=“wood/forest”, “matter/substance”), in reference to the association of species of this genus with Amazonian inundation forest habitats and the unique suite of characters uniting the two species, and Tachys, the nominate genus of the subtribe Tachyina.

Holotype: male (UASM) with following label data: “BRASIL Amazonas / Rio Negro Cucui / varzea forest / Sept. 17, 1978 // BRASIL EXP. / 1978 / G.E.& K.E. Ball / Collectors”. Paratypes: 5 (2 male, 3 female) in UASM, ZSM from the type locality [1♂, UASM], “Brasilien / Tapurucuara am / Rio Negro/Amazonas / 7 11.1963 / C. Lindemann” [1♂, 1♀, ZSM], “BRASIL Amazonas / Rio Demiti, ca. / 0°53'N 66°57'W / “La Laguna” / Varzea forest / Sept. 13, 1978 // BRASIL EXP. / 1978 / G.E.& K.E. Ball / Collectors” [1♀, UASM], BRASIL Amazonas / ca. 10 km. n.e. / São Gabriel da / Cachoeira, stream / margin, forest / Sept. 20, 1978 // BRASIL EXP. / 1978 / G.E.& K.E. Ball / Collectors” [1♀, UASM].

Brazil: Amazonas, Rio Negro Cucui.

Head and abdomen as in description of the genus.

Size. ABL = 3.2–3.3 mm; SBL = 3.3–3.4 mm; TW = 1.4–1.5 mm.

Form. (Fig. 2E) Large, elongate, subdepressed.

Color. Uniformly dark brown and slightly iridescent.

Microsculpture. Pronotum and elytron with very fine, linear, transverse microsculpture; head with coarse, isodiametric microsculpture.

Prothorax. Pronotum (Fig. 3E) transversely quadrate, wider than long.

Pterothorax. Elytra broad and parallel-sided, narrowed beginning at apical third, 5–6 visible strial interneurs, first two complete (Fig. 2E); i5 originating at tip of elytral basal margin and separating basal elytral disc from humeral region; otherwise as in description of the genus.

Genitalia. Male (Fig. 6A): median lobe elongate, with slender brush-shaped internal sclerite; left and right parameres both broad and paddle-shaped apically, each with 5 long apical setae; right paramere smaller. Female: not examined.

Known from Brazil, Ecuador, and Colombia.

Patronym in honor of George and Kay Ball, who collected the major part of the type series on their 1978 expedition to Brazil.

The habitat of this species was mistakenly regarded as várzea. In fact the specimens were collected in igapó forest (Ball, personal communication, 2016)

Holotype: male (NMNH) with following label data: “PERU: MADRE DE DIOS / Rio Manu, BIOLAT Biol. Sta. / Pakitza, 356m, 16 Oct. 1989 / 11°56°47'S 071°17°00'W / T.L. Erwin Trocha Pacal /21”. Paratypes: 1 female, in NMNH, from “PERU: MADRE DE DIOS / Rio Manu, BIOLAT Biol. Sta. / Pakitza, 356m, 25 June 1993 / 11°56°47'S 071°17°00'W / T.L. Erwin & F. Pfuno // Treading red-colored leaf litter / at edge of lake shore in sunny / area Tr. Gallareta Lot 524’.

Perú: Madre de Dios: Rio Manu, BIOLAT Biol. Sta., Pakitza, 11°56°47'S 071°17°00'W, 356m.

Head and abdomen as in description of the genus.

Size. ABL = 2.7–2.85 mm; SBL = 2.8–2.9 mm; TW = 1.2–1.3 mm.

Form. Head and prothorax slender, elytra rounded and convex.

Color. Uniformly rufotestaceous, shiny.

Microsculpture. Head, pronotum and elytron smooth, glabrous.

Prothorax. Pronotum subequal in length and width.

Pterothorax. Elytra somewhat round and convex, each with 2–3 visible strial interneurs, only i1 completely impressed; i5 position without visible stria, but with gently sloping “shelf” which originates at tip of elytral basal margin and separates basal elytral disc from humeral region.

Genitalia. Not examined.

Known only from the type locality in the Madre de Dios region of southeastern Perú.

Latin rubrum (=“red/crimson”), in reference to the deep red-brown color of this species.

Note: The holotype will be deposited in UNMSM and is currently held in trust until the completion of studies at NMNH.

Bembidium ephippiatum Say, 1834.

Mentum with paired foveae; pronotum with continuous, punctate transverse impression; basal transverse impression arcuate or lobed, forming crescent-shaped or bilobed basal section; elytron either with one to two conspicuous subhumeral fovea(e) along i8 in basal fourth or with 8 entirely punctate interneurs; elytra with or without color pattern. ABL = 1.72–3.72 mm. (Erwin 1974a; Erwin et al. 2002).

Australia and the Americas.

Bembidium ephippiatum Say, 1834.

Typically elongate, subcylindrical in form; pronotum quadrate to narrowed in basal fourth; elytral i8 with a deep fovea at or just anterior to midpoint of elytron and two smaller, subhumeral foveae of variable size; elytral interneurs punctate to striatiopunctate; elytra usually testaceous with darker markings resembling ink blotches. ABL = 1.88–3.72 mm. (Erwin 1974a; Erwin et al. 2002).

Species of this subgenus are numerous and described from across the New World between the temperate mid-latitudes of North and South America and some of the Caribbean islands.

Trechus brasiliensis Sahlberg, 1844.

Broad and robust, depressed to subcylindrical in form; pronotum quadrate, subequal in width at base and apex; elytra usually unicolorous; elytral interneurs punctate; i8 subsulcate and not bearing fovea(e) at or near middle of elytron; i8 with or without subhumeral fovea: if present, then fovea shallow and bearing seta or small, perforate, and located at basal fourth near seta Eo4; if i8 lacking posthumeral foveae, elytron with 8 entirely punctate interneurs. ABL = 1.84–3.04 mm. (Erwin 1974a; Erwin et al. 2002).

Species of this subgenus are restricted to the New World, described from México south to Argentina and some of the Caribbean islands.