Drapetis Meigen, 1822

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 : 53-54

Genus Drapetis Meigen, 1822

Drapetis Meigen, 1822: 91 . Type-species: D. exilis Meigen, 1822 , by monotypy.

Caecula Gistl, 1848 : IX. An unnecessary new name for Drapetis . Type-species: Drapetis exilis Meigen, 1822 , automatic.

Arbicola Gistl, 1848: 152 . An unnecessary new name for Drapetis . Type-species: Drapetis exilis Meigen, 1822 , automatic.

Recognition

The genus Drapetis can be distinguished from other genera of the Drapetini by the following combination of the characters: head close-set upon thorax, gena very narrow, antennae upturned, postpedicel more or less rounded ventrally; wing with Rs long, abdominal tergites with squamiform setae, intersegmental modifications present.

Diagnosis

Small (about 1.5 mm) shining black robust flies. Head closely set upon thorax. Frons with sides divergent above. Eyes contiguous on face. One pair of vertical bristles. Ocellar tubercle with 2 pairs of bristles. Antennae upturned, pedicel with circlet of subequally short setae; postpedicel usually short and rather ovate with lower margin convex; stylus arising apically, arista-like, long. Gena linear. Palpus small, with short subapical seta; lacking sensory pit. Thorax largely shining, anepisternum with small hairs or bristles at least in upper posterior corner or bare. Postpronotal bristle not prominent. Mesonotal bristles very prominent but acrostichals and dorsocentrals undifferentiated; no setae between mid and hind coxae. Legs short, robust, lacking prominent bristles. Wings normally developed; finely infuscate; Rs long, originating before midway of R 1; R 1 meeting costa at middle of wing; R 2+3 complete, meeting costa beyond middle of wing; R 4+5 and M 1+2 more or less parallel near wing margin; A 1 present as fold; crossvein CuA 2 absent; crossvein bm-cu somewhat oblique or transverse; cell br shorter than cell bm. Abdomen with some tergites modified or unmodified; squamiform setae present; gland-like intersegmental structures absent. Terminalia with epandrium completely divided; left epandrial lamella fused to hypandrium; left surstylus differentiated from epandrial lamella, divided; right surstylus differentiated from epandrial lamella; cerci separated; hypoproct unmodified; hypandrium setose subapically or bare; phallus short; usually two rod-shaped apodemes (i.e. ejaculatory and ventral apodemes) present. Female similar to male; terminalia elongate; tergite 8 separated from sternite 8; cercus elongate ovate.

Remarks

Currently, Drapetis includes about 80 species worldwide, with 18 species known from the Oriental Region. In contrast to its sister genus Elaphropeza , Drapetis is not common in Singapore. Locally, however, representatives of this genus can be very abundant and several species coexist. This is particularly true for the mangrove at Chek Jawa where wrack mainly composed of decomposing green algae is washed onto the shoreline and wild boars dig in the sand. At this site we found three species of Drapetis together in large numbers. They were active on sand that was disturbed by the wild boars and that was enriched with pieces of decomposed wrack. Four of the five species of Drapetis that we recorded in Singapore are mangrove species. Drapetis hutan sp. nov. is the single record of a species occurring in rain forest. This would suggest that Drapetis having a mainly Palaearctic distribution, radiated and thrived in mangroves in Southeast Asia and was less successful in rain forests.

Key to species of Drapetis from Singapore

1. Postpedicel ventrally rounded with dorsoapical stylus ( Fig. 105 ), at most 1.5 times as long as wide. Palpus and proboscis brownish yellow. Halter yellow. Hind femur brownish in apical 2/3, otherwise legs yellow............................................................................................ D. mandai sp. nov.

– Postpedicel elongate, almost conical, 2.5-3.0 times as long as wide with nearly apical stylus ( Fig. 93 ). Different combination of characters...........................................................................................2

2. Palpus white (at most yellowish).........................................................................................................3

– Palpus black..........................................................................................................................................4

3. Labrum brown. Hind femur swollen, with row of long pale brown anteroventral bristles on apical quarter........................................................................................................................ D. laut sp. nov.

– Labrum white. Hind femur slender, with only 2-3 dark subapical anteroventral bristles............. .................................................................................................................................. D. bakau sp. nov.

4. Halter pale. Hind femur yellow in male; hind tibia weakly curved and as long as hind femur, hind tarsomere 1 with 2-3 black ventral spinules at base......................................... D. pantai sp. nov.

– Halter with dark brown knob. Hind femur completely black; hind tibia strongly curved and much shorter than femur; hind tarsomere 1 without ventral spinules at base.................. D. hutan sp. nov.

Figures

Figs 105-107. Drapetis pantai sp. nov., ♂ terminalia. 105. right surstylus, dorsal view. 106. epandrium and cerci, dorsal view. 107. left surstylus, lateral view.

Figs 92-93. Hind leg of Drapetis, ♂, anterior view. 92. D. pantai sp. nov. 93. D. bakau sp. nov.