Pseudeurybata Hennig 1935

Marshall, S. A., 2016, Revision of the genus Pseudeurybata Hennig (Diptera, Micropezidae, Taeniapterinae), Zootaxa 4132 (2), pp. 254-268 : 255-256

Pseudeurybata Hennig 1935

Type (monotypy) Pseudeurybata stigmatica Hennig, 1935: 28 Pseudeurybata Hennig 1934: 72 (nomen nudum)

Diagnosis. Relatively large (11–17mm), reddish to dark brown flies; wing usually uniformly infuscated (with an apical spot in P. stigmatica ), head mostly orange with similarly textured and pigmented lower frontal vitta and lower orbital strip; anterior part of clypeus large with lower surface characteristically deflexed. Inner vertical, outer vertical, and postocellar setae usually well developed (postocellar seta absent in P. zeta ).

Description. Head. Dull orange in ground colour, ocellar triangle black or dark brown, epicephalon often shining or partly shining and darker than frontal vitta (shining brown in P. compeditis ), lower frontal vitta identical in colour and texture to orbital strips, upper frontal vitta (behind ocelli) usually distinct from epicephalon. Head chaetotaxy including inner and outer vertical setae, postocellar setae (absent in P. z e t a only), one upper frontoorbital setae and 1–2 lower fronto orbital setae. Ocelli closer to anterior margin of frons than to vertex. Arista bare or almost so (sometimes with minute setulae near base), arising dorsobasally, first aristomere swollen. Pedicel without long setae. Palpus narrow, parallel-sided. Face yellow, membranous; clypeus shining, convex, lower surface deflexed, usually bare but sometimes ( P. alces , P. compeditis , P. z e t a) with fine pale setulae. Gena with white pruinose strip under eye.

Thorax. Varying from slightly to conspicuously depressed anterior to suture, anterior margin of mesonotum vertical. Cervical sclerite large, subquadrate. Lower margin of proepisternum bicolored (dark above, pale below), with a marginal row of strong setae. Postpronotal lobe distinct, depressed, with some small setae on outer part and a dark ridge at anteroventral and sometimes posteroventral margin. Anepisternum and anterior part of katepisternum usually with sparse small dark setae. Two strong notopleural setae, one (presutural) dorsocentral seta, one prealar seta, one postalar seta. Acrostical setulae in a distinct dorsocentral row and indistinct medial rows. Scutellum with strong apical setae and small discal setulae. Katepisternum with 2 posterior vertical rows of setae, posteriormost row stronger and extending along posterior and posterodorsal surfaces of katepisternum. Outer surfaces of mid and hind tibia with a weak longitudinal groove on basal fifth to third. Apex of fore and hind tibia with a dense apicoventral comb of short, flattened golden setae. Tarsomere one on all legs slightly longer than tarsomeres 2–5 combined. Wing usually evenly infuscated, without clear areas (but wing of P. stigmatica clear with a dark apical spot); second costal sector very long, 4– 5 X third costal sector; distal part of anal cell forming an equilateral triangle, CuA2 distinctly proximal to crossvein bm. Costagium with uniformly small setae.

Abdomen. Slightly constricted at base, syntergite 1+2 slightly longer than tergite 3, tergites sclerotized and pigmented. Pleuron variable between species in color but often darkly pigmented on upper half only. Oviscape variable in dimensions and colour between species, but usually stout at base, abruptly narrowed and darkened distally. Bursa copulatrix broad, rugose dorsally, with a basally broad and distally small and nipple-like ventral receptacle ( Fig. 5 ). Female spermathecae and associated structures species-specific, usually with 2 spermathecal ducts arising independently from a short bursa copulatrix, the smaller one leading to a single small spermathecae and the larger one leading to small swelling before branching into paired spermathecae (bursa extended into a broad common duct only in P. z e t a). Male abdomen with syntergite 1+2 long (about 2.5X T3), at least upper part of pleuron of segment 2 forming a pleural sac (greatly extended in some specimens, usually darkly setulose above). Internal male genitalia with a short, broad distiphallus terminating in a very large phallic bulb (except in P. zeta , in which there is a short, sinuate distal distiphallus beyond the phallic bulb). Epandrium small, cercus well developed; genital fork of sternite 5 variable, arms straight or incurved with or without prominent basal processes or teeth, sometimes enlarged with arched or strongly arched arms with elongate basal processes.

Comments. The Central American species of Pseudeurybata form a cohesive group characterized by similarities of the male and female terminalia, chaetotaxy and the diagnostic deflexed clypeus. As discussed further below, the single South American species (P. z e t a new species) has the diagnostic deflexed clypeus but is otherwise an outlier that differs widely in several characters, including the structure of the female bursa copulatrix, the structure of the male distiphallus, and the chaetotaxy of the head.

With the exception of P. z e t a, most Pseudeurybata species are brown, with the head and thorax similar in color and with postocellar, inner vertical and outer vertical bristles present. Scipopus species are usually black with a red head, and other members of the Scipopus group usually lack either outer vertical or postocellar bristles. But the only external morphological character that reliably diagnoses all Pseudeurybata is the expanded and ventrally deflexed anterior clypeus. The height of the anterior face of the clypeus is at least 0.4X the length of the posterior arms, in contrast with related genera in which the face of the clypeus is relatively narrow, no more than 0.3X the length of the posterior arms.

Figures

FIGURES 1 – 7. Pseudeurybata alces. 1, female on foliage; 2, head and anterior thorax, dorsal view; 3, 4, female ovipositing in mossy log; 5, spermathecae and associated structures, lateral view; 6, apex of male abdomen, lateral view; 7, male terminalia, lateral view. Abbreviations: BDP—basal distiphallus, PB—phallic bulb, BC—bursa copulatrix, C—cercus, PD—paired spermathecal duct, VR—ventral receptacle.