Diochus antennalis CAMERON, 1922

Irmler, Ulrich, 2017, A review of the Neotropical genus Diochus ERICHSON, 1840 (Coleoptera: Staphylinidae: Staphylininae), Beiträge Zur Entomologie = Contributions to Entomology 67 (1), pp. 1-62 : 9-10

Diochus antennalis CAMERON, 1922

Figs 11A–C , 38H , 42A

Diochus antennalis CAMERON, 1922: 116

Type material examined: Syntypes: Grenada: 2 males, 2 females, Balthazar (Windward side), leg. H.H. Smith , #135, #72, #40, #339; 1 female, Mount Gay East (Leeward side), W.I., leg. H.H. Smith , #241; 1 female, Chantilly Est. (Windward side), W.I., leg. H.H. Smith , # 211. The male #135 was selected as lectotype ( BMNH) .

Additional material examined: Grenada: 2 males, Chantilly Est. (Windward side), W.I., leg. H.H. Smith , #10,

#339 ( NMW); Costa Rica: Guanacaste Prov., Nicoya Peninsula, Rd. Playa Grande> Matapalo (10°20.30'– 21.14'N, 85°48.46'–50.43'W), 10–80 m elev., forest remnants, meadows, fincas, collected by car net, male, 15.12.2013, leg. Schülke & Grünberg ( UIC) ; Heredia Prov., 3 km S Puerto Viejo , OTS La Selva, 100 m elev., male, Oct. 1992, leg. P. Hanson ( KNHM) ; Columbia: Vichada , PNN El Tuparro Cerro Tomás (5°21'N, 67°51'W), 140 m elev., malaise trap, 8.– 18.8.2000, leg. W. Villalba #M513 ( KNHM) ; Guyana: Kurupukari (4°40'N, 58°40'W), Malaise trap / flight intercept trap, male, Sept.-Nov. 1992 ( BMNH) ; Bolivia: Santa Cruz Dept., Saavedra, Agr. Exp. Sta. , blacklight trap, male, 28.12.1959, leg. R.B. Cumming ( FMNH) .

Diagnosis: The parameres of D. antennalis resemble those of the D. schaumii-group, because they are slightly widened at apex. However, the endophallus with the funnel-like widened basal inner duct and the presence of an apical inner duct show that it belongs to the D. inornatus-group. It is one of the smallest species of the group known so far. Only D. tricolor is similarily small. It can be differentiated from that species by the unicoloured yellow colouration and the different shape of the paramere. In contrast to D. tricolor , D. antennalis has a weak microsculpture on the vertex.

Description: Length: 3.1 mm. Colouration: light brown; head and abdominal segments III–VI slightly darker; legs and antennae yellow, except penultimate antennomeres indistinctly darker.

Head 0.44 mm long, 0.32 mm wide; eyes not prominent; small; EL: HL = 0.22; temples 2.5 times as long as eyes; temples divergent to posterior angles; PW: EW = 1.25; posterior angles shortly rounded; posterior margin slightly concave; setiferous punctation moderately dense and deep; clypeus irregularly punctate; vertex with moderately wide impunctate midline; adjacent to midline with row of five punctures, divergent to anterior edge of eyes; between central row and eyes with irregular supraocular punctation; temples more densely punctate; transversely or diagonally striate microsculpture extremely weak; surface shiny.

Antennae slightly longer than head and half of pronotum combined; first antennomere thicker and longer than following antennomeres; second and third antennomere conical; approximately twice as long as at their apical width; length of following antennomeres decreasing; fourth slightly longer than wide; approximately 1.5 times as wide as long; all antennomeres pubescent and with apical setae.

Pronotum 0.51 mm long, 0.41 mm wide; widest near middle; sides approximately parallel; anterior margin convergent to small neck; slightly convergent to shortly rounded posterior margin; posterior margin slightly convex; lateral margin fine; in dorsal aspect, visible in posterior third; setiferous punctation sparse; transverse row of four punctures divergent posteriad; in posterior half two pairs of punctures; close to anterior angles another puncture and several setiferous punctures along lateral margin; without microsculpture, but with sparse irregular micro-punctures; surface polished.

Elytra 0.51 mm long, 0.53 mm wide; sides divergent to posterior angles; shoulders obtuse; posterior angles nearly rectangular; posterior margin slightly triangularly emarginate; setiferous punctation in irregular rows of five to six punctures; inner row adjacent to suture line; two additional lateral rows in equal distance; several punctures along lateral margin; irregular coriaceous ground sculpture weak; surface less shiny than head and pronotum.

Abdomen densely pubescent.

Aedeagus with thick seminal vesical, sligtly longer than half of central lobe, basal inner duct with funnel-like apical widened forceps; apical inner duct filamentous; with one coil; paramere slender; slightly widened at apex to triangular transparent plate; at apex with three long setae; base of shaft with four sensillae.

Spermatheca 0.30 mm long, 0.25 mm wide; bursa copulatrix in central position to coiled duct; coiled duct with numerous regular coils.

Figures

Figs 42: Fore-bodies of Diochus antennalis (A), D. tricolor (B), D. amazonensis (C), D. hermani (D), D. plaumanni (E), D. hibbsi (F), D. newtoni (G), D. novus (H); scale bar: 0.5 mm.

Figs 10–13: Diochus inornatus-group: of D. vicinus (10), D. antennalis (11), D. novus (12), D. tricolor (13); aedeagus (A),

Fig. 38: Spermathecae of Diochus longicornis-group: D. longicornis (A), D. tarsalis (B), D. ashei (C), D. guianensis (D), D. unicolor (E); Diochus inornatus-group: D. inornatus (F), D. hanagarthi (G), D. antennalis (lateral aspect H), D. hermani (I), D. hibbsi (J), D. newtoni (K), D. novus (L); scale bar: 0.1 mm.