Gymnochiromyia Hendel, 1933

Ebejer, M. J., 2008, New species of Gymnochiromyia Hendel, 1933 (Diptera: Schizophora: Chyromyidae) from Southern Africa, African Invertebrates 49 (1), pp. 77-77 : 81-83

Genus Gymnochiromyia Hendel, 1933

Gymnochiromyia Hendel, 1933: 43 .

Type species: Peletohila minima Becker, 1904

(= Antophilina flavella Zetterstedt, 1848 ), by designation of Hendel.

Diagnosis: The following combination of characters not previously noted by earlier workers separates Gymnochiromyia with greater confidence from other genera in the family. The ocp is flat or concave when viewed from above. This character is shared with other genera including Aphaniosoma , but not Chyromya . The disc of the ocp is entirely or largely bare, quite unlike Chyromya which is strongly setose. Only Aphaniosoma has an intrahumeral seta or setula and this is usually incurved. Gymnochiromyia usually has no pra and no posterior ia; these are present separately or together in some other genera. Gymnochiromyia has oval eyes with the longest axis positioned horizontally or only slightly obliquely ( Chyromya has round eyes; Aphaniosoma and undescribed genera have very obliquely placed oval eyes). The frons in most species of Gymnochiromyia protrudes above the antennae so that it is clearly visible in profile, often markedly so and thus, in most species, the head is longer above than it is below. In Aphaniosoma , an apicoventral seta on the mid tibia is always clearly longer than the diameter of the tibia at apex. This seta may be present in Somatiosoma and a closely related undescribed genus, but it does not exceed the diameter of the tibia and is generally less conspicuous. It is absent in Chyromya and Gymnochiromyia . There are only two exceptions to this combination of character states. In the species treated below, G. pretoriella and G. maculipennis have a weak pra (in the latter species it is only present in the holotype). None of the Palaearctic species of Gymnochiromyia has a pra. In all other respects these two species fit in Gymnochiromyia .

Description:

Head ( Fig. 6 ): Predominantly yellow, fr protruding beyond anterior eye margin, sides converging towards antennae; gena wide with rounded lower margin, vibrissal angle poorly differentiated; face depressed, poorly sclerotised, except for a narrow median line, carina never properly developed although this sclerotised median line may give the impression in some specimens that a shallow carina exists; ocp flat to concave when viewed from above, in profile usually barely visible behind eye margin, on lower part, behind gena with a distinct pale seta directed downwards; chaetotaxy: 3 welldeveloped orb, anterior inclinate; 1 strong vti and 1 strong vte, oc divergent, pvt distinct and convergent or crossed; fr, across middle, often with very fine pale setulae, short setulae also on post oc margin, but none on disc of ocp; gena finely, but distinctly setulose; 2 to 3 short vibrissal setulae. Antenna with round third segment, first and second segments short, latter with seta dorsally; arista 3-segmented, usually bare, sometimes very short pubescent.

Thorax: Ground colour predominantly yellow; msn with or without stripes; mtn often dark; pleura sometimes with brown on stpl and hypl; chaetotaxy: 1–2 hu, 1 psthu, 0+1 to 1+4 dc, acrs in 4–8 rows with a strong prescut pair, 1 sa and 1 pa, 2 ntpl, ia and pra usually absent, if a posterior ia present this is always shorter than prescutellar acrs; 1 mspl at middle of hind margin and 1 stpl at upper posterior corner, pteropleurals absent.

Wing ( Fig. 1 ): Hyaline (pigmented patch in one species), uniformly microtrichose except for basal half of subcostal cell; costa broken at weakly sclerotised humeral crossvein and at R 1; subcosta merges with R 1 just before this reaches costa; veins R 4+5 and M 1+2 parallel to wing margin or very slightly convergent; costa ends almost exactly at end of vein R 4+5; costal setulae very short and of uniform length, sometimes a few setulae are longer than others at base of wing along anterior edge just before R 1 merges with costa; mixed in randomly amongst the pale costal setulae are darker and thicker setulae appearing as minute spines, reminiscent of the costa of Heleomyzidae ; 6–12 dark setulae set at intervals along dorsal aspect of costa between R 1 and apex of R 2+3.

Legs: Yellow and short setulose except front femur where longer posterodorsal and posteroventral setae may be present; mid tibia never with long apicoventral seta; claws black in apical half or more, pulvilli normal.

Abdomen: Predominantly yellow in most species; sparse short setulose on all segments; tergites well sclerotised; st from poorly sclerotised to wholly membraneous and very thinly and microscopically setulose.

Male postabdomen: tg 6 distinct from ep, but narrower than tg 5 and ventral margin may be narrowed almost to a point; pregenital st not modified; prg always distinct and most often distinctly setulose, fused to hypandrium or joined to it by a short membrane, never with an intermediate sclerite; psg and bac scl not always discernible, but in those species where these structures have been identified, they are small and simple when compared to other genera; ej apd often sclerotised and tubule to basiphallus sometimes visible; distiphallus usually large and of complicated structure, mostly membranous, but with several sclerotised plates; cercus always small, narrowly separated and finely setulose; surstylus usually separated from ep.

Female postabdomen: Segment 8 with only st sclerotised and in most species this is divided into two lateral plates; subanal plate (sap) present, small, poorly sclerotised and often with very fine setulae on minute papillae; supra-anal plate not developed; 2 small (0.04–0.07 mm) spermathecae dark coloured (grey, brown or black) lying deep to lateral aspect of tg 6 or 7; spermathecal ducts not sclerotised or pigmented.

Length: ♂ and ♀1.2 –2.2 mm; wing 1.2–2.0 mm.

Figures

Figs 5, 6. G. capensis sp. n.: (5) male hypopygium, lateral view; (6) head, lateral view. Scale bars = 0.2 mm.

Fig. 1. Gymnochiromyia maculiventris sp. n., wing. Scale bar = 1 mm.