Chersodromia sylvicola, Grootaert & Shamshev, 2012

Grootaert, Patrick & Shamshev, Igor V., 2012, The fast-running flies (Diptera, Hybotidae, Tachydromiinae) of Singapore and adjacent regions, European Journal of Taxonomy 5, pp. 1-162 : 29-31

Chersodromia sylvicola sp. nov.

Figs 44-51

Diagnosis

Occiput pale yellowish; 1 pair of strong verticals longer than ocellars; antennal stylus apical, postpedicel fusiform; hind tibia with 4 bristles on apical half.

Description

Male LENGTH. Body 1.2 mm; wing 0.98 mm.

HEAD. Entirely pale-yellowish in ground-colour, almost white, including frons, occiput, ocellar tubercle, face, gena, palpus and proboscis; eyes and ocelli contrastingly black; with pale yellowish setation. Frons broadly triangular, above antennae as wide as pedicel. Eyes contiguous on face; ommatidia enlarged anteriorly and on lower half of eye. Anterior and posterior pair of ocellars long (as long as basal antennal segments combined). One pair of strong verticals, slightly longer than ocellars. Gena narrow. Occiput concave above neck, pale yellowish. Antenna ( Fig. 44 ) yellow, stylus brown; pedicel with long seta ventrally; postpedicel fusiform, as long as pedicel; stylus apical, about 2.5 times as long as basal segments combined. Palpus small, white, with subapical seta and some additional setulae; small round sensory pit present.

THORAX. Pale yellow in ground-colour; mesonotum and pleura uniformly yellowish without colour pattern; with yellowish setation. Postpronotal lobe with 1 long inclinate bristle. Mesonotum with 1 short presutural supra-alar, 2 notopleurals, 2-3 minute postsutural supra-alars, 1 postalar and 2 apical scutellars (shorter than base of scutellum); acrostichals inconspicuous, 4 pairs almost on one line; 3 long dorsocentrals and 1 short prescutellar.

LEGS. Uniformly pale yellow. Fore femur thickened on basal 3/4; with row of pale posteroventral bristles and 2 long ventral bristles near base. Fore tibia with distinct ventral preapical bristle. Mid femur half as stout as fore femur, with strong brown, anterior preapical bristle. Mid tibia with some spinule-like

setae on apical half and 1 long posteroventral subapical bristle. Hind femur slightly stouter than mid femur, with 1 very long thin ventral bristle near base. Hind tibia ( Fig. 51 ) with 4 long yellowish bristles somewhat longer than width of tibia, with 1 anterodorsal, 2 dorsal and 1 short ventral subapical bristles.

WING. ( Fig. 45 ) Normally developed, faintly yellowish grey tinged, with pale veins. Costal bristle rather short, pale brown. Vein Rs rather long, nearly 1.5 times as long as crossvein bm-cu. R 2+3 short, about 2.0 times as long as distal portion of R1 (between Rs and meeting point with costa), meeting costa before middle of wing. R 4+5 and M 1+2 straight and parallel near wing tip. Crossvein bm-cu strongly oblique. Crossveins r-m and bm-cu separated. Cell br somewhat shorter than cell bm. Anal vein absent. Calypter minute, brown, with 2 brown cilia. Halter with white knob.

ABDOMEN. White, with pale short setation; tergite 1 weakly sclerotised, following tergites normally sclerotised; no intersegmental gland-like structures and squamiform setae. Terminalia ( Figs 48-50 ) elongate. Cerci rather stout, with unmodified setation. Epandrium completely divided. Right epandrial lamella with unmodified setation. Right surstylus bilobed ( Fig. 48 ). Left epandrial lamella fused with hypandrium, with unmodified setation. Left surstylus not prominent. Phallus short, tubiform, ending in fine tip. One rod-shaped apodeme present.

Female

Unknown.

Material examined

Holotype ♂

SINGAPORE: Nee Soon, 8 July 2005, Mal. 2 (reg. 25206, leg. P.G.; in ZRC).

Etymology

The name refers to its occurrence in the forest.

Distribution

Singapore.

Habitat and seasonal occurrence

Forest, single record from beginning of July.

Remarks

Although Chersodromia sylvicola sp. nov. is also a yellow species that we consider belonging to the C.

flavicaput group, it is quite distinct from the three other known yellow species ( C. bulohensis sp. nov., C. flavicaput and C. obscura ) that resemble one another very much. The main difference from the latter three species is the presence of one pair of long vertical bristles, only one rod-shaped genitalic apodeme and the absence of a faint colour pattern (darker vitta) on the scutum.

Figures

Figs 44-51. Chersodromia sylvicola sp. nov., ♂. 44. antenna, lateral view. 45. wing, dorsal view. 46. head, lateral view. 47. head, frontal view. 48. right epandrial lamella, lateral view. 49. epandrium with cerci, dorsal view. 50. left surstylus, lateral view. 51. hind tibia, anterior view.