Chersodromia obscura, Grootaert, Patrick, Cumming, Jeffrey & Shamshev, Igor, 2007

Grootaert, Patrick, Cumming, Jeffrey & Shamshev, Igor, 2007, Non-marine Chersodromia Walker from Southeast Asia and Papua New Guinea (Diptera, Empidoidea, Hybotidae), Zootaxa 1661, pp. 55-61 : 59

Chersodromia obscura sp. nov.

( Figs 10–12 )

Diagnosis. Occiput dark yellowish in ground-colour. One pair of distinct vertical bristles. No acrostichals. Hind tibia with only 3 long bristles in apical half.

Description. Male. Body length 1.3 mm, wing length 1.25 mm. Head dark yellowish in ground-colour, but face, genae, palpi and proboscis pale yellow; eyes contrastingly black. Frons broadly triangular; in front as wide as antennal pedicel, strongly widening towards ocellar triangle. Eyes touching on face, with ommatidia enlarged on lower half of eye. Anterior ocellars long, brown; posterior ocellars as long. One pair of shorter vertical bristles. Postoculars brown, uniserial. Gena broad. Occiput somewhat concave above neck. Antenna with scape and pedicel brownish, postpedicel paler; pedicel with 1 long brown bristle ventrally; postpedicel smaller than pedicel; style at least 4 times as long as pedicel and postpedicel combined. Palpus small, with 1 pale terminal bristle and some hairs.

Thorax largely yellow, with dark brown bristles and hairs. Scutum in anterior third with brown median vitta broadly connected near middle with broad brown area at each side, leaving sides of notopleura and prescutellar depression yellow; scutellum with brown margin; katepisternum (= sternopleuron) anteriorly and meron (= hypopleuron) with dark brown patch. Postpronotal lobe with 1 long inclinate bristle. Mesonotum with 1 short presutural supra-alar, 2 notopleurals, 1 postsutural supra-alar, 1 postalar and 2 scutellars (with 1 hair on each side); acrostichals lacking; 3 long dorsocentrals.

Wings faintly greyish tinged, with pale brown veins, vein R2+3 darker. Costal bristle rather short, brown. Vein Rs nearly as long as crossvein bm-cu. R2+3 very short, meeting costa before wing midway. Vein M turning up just before ending near wing tip. Crossvein bm-cu strongly oblique. Crossvein r-m beyond cell bm. No anal vein. Squama minute. Halter with dusky knob.

Legs almost entirely yellowish-white, fore and mid tibiae and tip of hind femora somewhat darkened. Fore femur thickened on basal three quarters; with row of short brown posteroventral bristles and 2 long ventral bristles near base. Fore tibia with 1 distinct ventral preapical bristle. Mid femur half as stout as fore femur, with 1 long pale ventral bristle at base and 1 strong brown, anterior preapical bristle. Mid tibia with some weakly sclerotised spiny-bristles in apical half and 1 long posteroventral preapical bristle. Hind femur stouter than mid femur, with 1 very long fine basal ventral bristle. Hind tibia with 3 long black bristles: 1 anterodorsal, 1 dorsal and 1 anterodorsal preapical bristle.

Abdomen and terminalia ( Figs 10–12 ) very similar to C. flavicaput sp. nov. However, cercus longer, upper lobe of left surstylus with stronger spines and phallus less coiled at tip than in C. flavicaput sp. nov.

Female. Body length 1.2 mm, wing length 1.1–1.2 mm. Segment 8 moderately long; cercus yellow, with several brown hairs. Otherwise as in male.

Material examined: Holotype male: THAILAND, Ranong (Ranong prov.), Wat tapotaram up river (river banks in bamboo forest), 5.IV.1996, sample n° 96025, leg. P. Grootaert.

Paratypes: same data as in holotype, 2 females. All preserved in alcohol in the collections of the R.B.I.N.S., Brussels.

Derivatio nominis: The name " obscura " alludes to the slightly darker head.

Distribution. Thailand.

Remarks. Chersodromia obscura sp. nov. differs from C. flavicaput sp. nov. in having only 3 long bristles on the hind tibia while the latter has 5 bristles. In addition C. obscura sp. nov. has a pair of distinct vertical bristles, no acrostichals, stronger male cerci, longer spines on left surstylus, and tip of phallus is less coiled.

Figures

FIGURES 10 – 12. Chersodromia obscura sp. nov. (Ranong, Thailand; holotype male). 10. right epandrial lamella. 11. cerci and right epandrial lamella. 12. left epandrial lamella and left cercus. Scale 0.1 mm. lc: left cercus; ls: left surstylus; ph: phallus.