Mesoconius bicolor, Marshall, S. A., 2015

Marshall, S. A., 2015, Mesoconius Enderlein (Diptera, Micropezidae, Taeniapterinae) of Central America, Zootaxa 3914 (5), pp. 525-540 : 528-530

Mesoconius bicolor new species

Figs 1A–1 H

Description. Length (antenna to wing tip) 17–18 mm. Color: Abdomen orange except tip of female oviscape and posterolateral corners of T2–4; thorax orange to yellow on ventral third; head and thorax otherwise mostly black to blue–black except as follows: gena, extreme anteroventral corner of face and parafacial silvery pruinose, palpus orange–yellow, margin of frontal vitta silvery pruinose, scutum with a broad silvery longitudinal strip on each side, postsutural part of silver strip with a central dark oval patch. Fore tarsus white to yellow with white setae, hind tarsus white with mostly white setae on tarsomeres 1–4, dark setae ventrally on tarsomeres 3–4, mixed white and brown setae dorsally on tarsomere 5; fore femur orange basally, black distally; mid and hind femora orange with narrow, variably indistinct preapical and apical dark bands. Fore tibia black, mid tibia and hind tibia brown to yellow.

Head: Epicephalon and paracephalon shining, indistinctly striate, sharply contrasting with orbits and lower frons; frontal vitta velvety black, sharply constricted behind ocelli, then slightly expanded to a densely microtrichose area between postocellar bristles; widely separated from anterior margin of frons. Outer vertical bristle absent, inner vertical bristle strong, postocellar bristle strong. Fronto-orbital bristles (2) widely separated, upper fronto-orbital bristle very large, inserted on epicephalon well above orbital strip, lower fronto-orbital minute. Upper face bare, shining, strongly convex-carinate; parafacials, gena, and outer corner of face strongly silvery pruinose, subantennal areas shining black-brown. Palpus yellowish.

Thorax: Cervical sclerite with a vertical groove separating a microtrichose, subquadrate, indented posterior portion from a small bare anterior portion. Scutum with pruinose pattern of silvery areas as noted above, otherwise unevenly microsetulose with a central sparsely microsetulose strip flanked by scattered small acrostichal setulae; dorsocentral setulae sparse, not in distinct row; postpronotal lobe shining in contrast with microtrichose scutum, with some scattered small setulae, anterior margin forming a vertical, shining face, posterior margin rugose. Dorsocentral bristles strong, longer than scutellum (short in other species). Katatergite very prominent, with a tapered microtrichose apex. Vertical row of katepisternal bristles yellow. Coxae with anteroventral golden bristles.

Abdomen: Syntergite 1+2 very narrow basally, constriction between syntergites about half as wide as base of T3; length of T1+2 double length of T3.

Female abdomen: Pleuron pale. Oviscape reddish, dark at apex. Bursa copulatrix large, ventral receptacle elongate with a differentiated head. Single spermatheca small, slightly broader than duct; paired spermathecal duct similar in diameter to paired duct but longer and divided into a broad striate basal half and a narrower smooth distal half. Paired spermathecae elongate, distinctly striate, tapered basally, each duct beyond split with a subbasal elongate oval swelling and a distal section with an S–bend putting spermatheca at right angle to duct.

Male abdomen (described from photos of living flies and one male paratype with a damaged preabdomen): Tergite 5 unmodified. Sternite 5 lightly sclerotized, unmodified. Sternite 8 similar in size to epandrium. Epandrium with broad, sparsely setose posteroventral margin, cercus large and distinct. Hypandrium elongate, anterior plate narrow. Postgonites small and divergent (directed laterally), each with 2 equal small apical bristles. Basiphallus very small, frame-like; not extending beyond base of distiphallus. Basal part of distiphallus broadly tubular, gradually expanding to large phallic bulb forming a distinctive broad hood over base of distal part of distiphallus; distal part of distiphallus tapered and whip-like, apex broken on only available male. Ejaculatory apodeme very small, much smaller than epandrium and consisting largely of a swollen base and a narrow, parallel-sided apodeme.

Type material. Holotype (♀, INBC): COSTA RICA, Alajuela, San Ramon forest reserve, San Lorencito river, 5km N of Colonia Palmareña, 900 m. 13–18.vi.1993, I. Curso. Paratypes: COSTA RICA. Alajuela, San Ramon forest reserve, San Lorencito River, 900 m. 15.vi.1988, A. Solis (1 ♂, teneral, with ptilinum everted, INBC). Guanacaste, Z.P. Tenorio, Tierras Morenas, San Lorenzo River, 1050 m. viii.1994, Malaise, G. Rodriguez (1 ♀, INBC); Guanacaste, Pitilla station, 9km S Santa Cecilia, 700 m. x.1993, P.Ríos (1 ♀, INBC).

Additional locality (photo but no specimen, Fig. 1B ): COSTA RICA, Heredia, Rara Aves Nat. Res., 12km S Las Horquetas, 10˚17’00”N, 84˚02’50”W, 700 m. Feb 2005, S.A. Marshall (1♂, DEBU).

Etymology. The specific name of M. bicolor refers sharply bicolored body in which the thorax is orange below and dark above, and in which the dark upper thorax contrasts with the reddish abdomen.

Comments. Mesoconius bicolor is unusual amongst congeners for its occurrence at relatively low altitudes, ranging down to 700 m.

Figures

FIGURE 1 A – G Mesoconius bicolor. A, thorax – abdomen junction to show pointed katatergite; B, live male (Rara Aves, Costa Rica; not captured); C, male; D, male terminalia, lateral; E, spermatheca and associated structures, lateral; F, head; G, female; female thorax and abdomen.