Nanodromia Grootaert, 1994

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 : 112-113

Genus Nanodromia Grootaert, 1994

Nanodromia Grootaert, 1994: 142 .

Type-species: N. cryptica Grootaert, 1994 , by original designation.

Recognition

The genus Nanodromia can be distinguished from other genera of the Drapetini by the following combination of characters: postpedicel with dorsoapical extension, wing with Rs relatively short and originating closer to tip of R 1 than humeral crossvein, cells br and bm of subequal length, abdominal tergites lacking squamiform setae, intersegmental modifications present, two rod-shaped genitalic apodemes.

Diagnosis

Small flies with body length about 1.5 mm. Frons very broad, with sides divergent above. Eyes contiguous on face, lower ommatidia enlarged or ommatidia of subequal size. Two pairs of vertical bristles, but outer pair (sometimes both pairs) often hardly prominent. Ocellar tubercle with 2 pairs of bristles. Antenna with pedicel bearing long ventral subapical seta; postpedicel with dorsoapical extension; stylus arising dorsoapically, arista-like, long. Gena barely extended below eye. Palpus small, rounded, usually with short subapical seta. Thorax brown to black; sometimes modified ( N. narmkroi Grootaert & Shamshev ). Postpronotal bristle usually well prominent (except N. narmkroi ). Mesonotal bristles very prominent but sometimes acrostichals and dorsocentrals weakly differentiated. Anepisternum bare, rarely setose ( N. narmkroi ). Legs short; fore femur usually very thickened; mid legs usually with secondary sexual characters in male; hind tibia lacking prominent bristles. Wings usually normally developed or sometimes modified (non Oriental species); often with distinct pattern; Rs relatively short and originating closer to tip of R 1 than humeral crossvein; R 2+3 complete, meeting costa before middle of wing; R 4+5 and M 1+2 strongly divergent; A 1 absent; crossvein CuA 2 absent; crossvein bm-cu oblique; cells br and bm of subequal length; Halter with knob yellow to black. Abdomen with tergite 1 entirely pale; no squamiform setae; gland-like intersegmental structures present. Terminalia rotated 90° to right; epandrium completely divided; left epandrial lamella usually very narrow, separated from hypandrium, sometimes completely reduced ( N. narmkroi ); left surstylus undifferentiated from epandrial lamella, undivided, with unmodified setation; right epandrial lamella usually large, positioned ventrally; right surstylus present, slightly differentiated from epandrial lamella; cerci fused (sometimes incompletely), often bearing spines or papilla-like setae; hypandrium usually with 2 bristles on apical portion; phallus very short; two rod-shaped apodemes (i.e. ejaculatory and ventral apodemes) present. Female similar to male, but legs with unmodified structure and vestiture; terminalia short; tergite 8 fused laterally with sternite 8; sternite 8 without folded apex; cercus broad-ovate.

Remarks

The genus Nanodromia is known only from the Australasian (3 species from Papua New Guinea) and Oriental (6 species) regions ( Grootaert 1992; Grootaert & Shamshev 2003). Here Nanodromia is recorded for the first time from Singapore with three new species described below. There is an additional species with black legs known only from a single female ( Singapore, Sime forest 17 February 2006, forest, reg. 26034) that remains undescribed.

Nanodromia as its name indicates is a genus of very small flies, and hence identification is quite difficult. In addition many species resemble one another and leg colouration is sometimes variable. The position of the abdominal glands can be helpful in alcohol preserved specimens, but dissection of the male genitalia is often mandatory to confirm an unambiguous identification.

Key to species of Nanodromia from the Oriental Region

1. Scutum uniformly covered with hair-like setae (acrostichal and dorsocentral bristles undifferentiated)...................................................................................................................................2

– Acrostichal and dorsocentral bristles well differentiated in rows ( Thailand; Malaysia; Singapore).. .......................................................................................... N. narmkroi Grootaert & Shamshev, 2003

2. Legs uniformly yellow; mid femur with basal swelling ( Fig. 1 ) and mid tibia curved in dorsoventral plane ( Thailand)......................................... N. narmjeud Grootaert & Shamshev, 2003

– Legs with hind femur and (or) tibia brownish near middle (sometimes only faintly); mid femur slender or with basal swelling, but mid tibia always straight..........................................................3

3. Hind tibia unmodified. Gland-like structures present between tergites 4 and 5 and 5 and 6 ( Figs 176-177 )........................................................................................................................................4

– Hind tibia somewhat curved. Bladder-like structure opening between tergite 4 and 5 ( Fig. 175 ).....5

4. Mid femur with strong black bristle in anterior fourth; some curved spine-like ventral bristles near tip ( Thailand).................................................................... N. phukhao Grootaert & Shamshev, 2003

– Mid femur with yellow anterior preapical bristle only; without curved bristles ventrally ( Singapore) .................................................................................................................................... N. hutan sp. nov.

5. Hind tibia somewhat curved at tip; bearing squamiform setae on apical half ( Fig. 174 ) ( Thailand). ................................................................................................ N. taksin Grootaert & Shamshev, 2003

– Hind tibia only faintly twisted; lacking squamiform setae on apical half, but with single line of short spinules ( Fig. 173 ) ( Singapore)............................................................. N. spinulosa sp. nov.

Figures

Fig. 1. Singapore in the Oriental Region (after Grootaert, 2009). STMF = subtropical mixed forest; STD = subtropical desert and semidesert; TDFS = tropical dry forest and savannah; TWF = tropical wet forest. The Weber line is considered to form the southeast boundary of the Oriental Region.

Figs 172-177. Nanodromia, ♂. 172. N. hutan sp. nov., hind leg, anterior view. 173. N. hutan sp. nov., tip of hind tibia, dorsal view. 174. N. phukhao Grootaert & Shamshev, 2003, hind tibia, dorsal view. 175. N. narmjeud Grootaert & Shamshev, 2003, bladder-like gland between tergite 4 and 5, dorsal view. 176. N. narmkroi Grootaert & Shamshev, 2003, gland-like fields between tergites 4-5 and 5-6, dorsal view. 177. N. phukhao Grootaert & Shamshev, 2003, gland-like fields between tergites 4-5 and 5-6, dorsal view. (Figs 174-177 after Grootaert & Shamshev 2003).