Corononcodes dimorpha, Barraclough, 2001

Barraclough, D. A., 2001, A review of the South African species of Corononcodes Speiser (Diptera: Acroceridae), African Invertebrates 42, pp. 95-104 : 99-102

Corononcodes dimorpha sp. n.

( Figs 1–2 , 4–5 )

Etymology: Named for the sexual dimorphism in wing colour.

Holotype male: SOUTH AFRICA: Northern Cape: ‘ SOUTH AFRICA / Garies [30 ° 33'S: 17 ° 59'E] / Sept. 1970 / H. Townes’; ‘ HOLOTYPE male / Corononcodes / dimorpha sp. n. / Det. D. Barraclough, 2001’. In NMSA; in good condition.

Description: Based on male holotype and female paratype (same data as holotype).

Male:

Measurements (in mm): Total length, excluding antennae [7.2]; wing, from extreme base [4.9].

Head ( Fig. 1 ): Eyes and occiput blackish; occiput visible in dorsal view. Eye with pile covering full extent in profile (although absent antero-medially); pile on eye and occiput pale brown. Ocellar tubercle height one-fifth head-height; pile elongate, white; 3 ocelli, all yellow-brown, median ocellus about one-fifth size of lateral ocellus; ocellar tubercle variously rugose with 2 sublateral vertical ridges on anterior half, middle section not raised, paired and dorsally directed posterior projections in dorsal view. Scape and pedicel mainly dark brown; scape haired dorsally; pedicel a little longer than half length of scape, with short dorsal hairs; pile on scape and pedicel less than half length of that on eye, occiput and ocellar tubercle. Flagellum smoothly rounded apically; partly yellow-brown, otherwise dark brown (mostly dorsally); length about 1.3–1.4 times height of eye. Epistomal region reduced, slightly protruding anteriorly. Gena moderately developed in profile, depth at most two-thirds length of scape. Proboscidial covering dark brown; buccal cavity brown.

Thorax: Dark brown to black, pleura slightly paler. Pile white or pale yellow; absent below anepisternum, anepimeron and katatergite, also absent from entire anterior margin of anepisternum, extreme lateral corners of scutellum and from lower half of proepisternum; pile length almost reaching 2.0 times as long as on head. Pro- and metathoracic spiracles yellow. Haltere medium brown.

Legs: Coxae mainly medium to dark brown, pile white and slightly shorter than head pile, pile sparse on posterior surfaces of fore and mid coxae and largely absent on posterior surface of hind coxa. Trochanters mainly yellow-brown, pile white or yellow and shorter than coxal pile, very sparse on fore and mid trochanters and present on anterior surface of hind trochanter. Femora mainly yellow but brown anteroventrally, pile white and half to two-thirds as long as head pile, sparse to absent on posterior surfaces. Tibiae yellow, pile white, shorter and sparser than femoral pile; spurs weakly developed, comprising row of 7–10 tooth-like projections with one better developed than others, hind spur less than half length of scape. Tarsi yellow, pile shorter than tibial pile, but slightly longer dorsally at apex of each segment, pile markedly elongate dorsally at apex of fifth segment with length here almost reaching that of head pile. Claws dark brown to black; pulvilli yellow to yellow-brown.

Wing ( Fig. 4 ): Membrane hyaline. Veins mostly medium to dark brown, but subcosta mainly yellow-brown to brown. Vein M 3 incomplete, not originating from basal crossvein. Vein R 4+5 not reaching wing margin. Upper calypter entirely white pruinose. Lower calypter entirely hyaline; pile short, along outer margin.

Abdomen: Widest at TII. Mainly dark brown. Pile white, shorter than thoracic pile, more profuse on sternites, here sometimes appearing yellow.

Female:

Measurements (in mm): Total length, excluding antennae [7.3]; wing, from extreme base [6.1].

Head ( Fig. 2 ): Ocellar tubercle height one-quarter head height; pile yellow, absent posteriorly in profile; middle section conspicuously raised above lateral regions, height almost twice lateral margins. Flagellum entirely dark brown to black; length about 0.8– 0.9 times height of eye.

Legs: Fore coxa mainly yellow-brown. Pile present on anterior surface of each trochanter. Tibiae pale to medium brown. Spur comprising row of 7–8 tooth-like projections. Tarsi yellow-brown, pile at apex of fifth segment with length about two-thirds that of head pile.

Wing ( Fig. 5 ): Longer and more slender than in male. Membrane brownish infuscated. Upper calypter entirely brown pruinose.

Abdomen: Widest at TIII or TIV. Pile yellow to brown.

Discussion:A notable character of this species is the sexual dimorphism in wing colour, the membrane being entirely hyaline in the male and brownish infuscated in the female. The female also has the middle section of the ocellar tubercle more conspicuously elevated than in the male.As in C. homalostemma the flagellum is shorter in the female. It is the only South African Corononcodes species to have vein M 3 obviously incomplete and not attached to the basal crossvein.

Corononcodes dimorpha has been collected only at Garies, in Upland Succulent Karoo, near the west coast of the Northern Cape. The type series was kindly donated to the Natal Museum by Dr H. Geertsema of the University of Stellenbosch .

Figures

Figs 1–3. Corononcodes species, head profiles, showing details of all vestiture (note eye pile). 1. C. dimorpha sp. n., male. 2. C. dimorpha sp. n., female. 3. C. manningi sp. n., male.

Figs 4–6. Corononcodes species, wing, showing shape and venation. 4. C. dimorpha sp. n., male. 5. C. dimorpha sp. n., female (note: anal region folded upwards). 6. C. manningi sp. n., male.