Stilpon taksin, Shamshev & Grootaert, 2004

Shamshev, Igor V. & Grootaert, Patrick, 2004, A Review Of The Genus Stilpon Loew, 1859 (Empidoidea: Hybotidae) From The Oriental Region, Raffles Bulletin of Zoology 52 (2), pp. 315-346 : 327-328

Stilpon taksin , new species

( Figs. 36-39 )

Material examined. – Holotype - male, THAILAND: Songkhla province, Ban Di Luang , beach forest, sample n 97148, 30.Oct.1997, coll. P. Grootaert (coll. RBINS).

Paratypes – 1 male, 1 female, same data as in holotype ( RBINS) .

Diagnosis. – Species with yellow thorax, most similar to S. nhamyaaw . Differs primarily from its by indistinct pattern of wing and setose left cercus of male terminalia.

Description. – Male. Head black in ground-colour, with minute ocellars and hardly prominent inner verticals. Antenna yellow. Postpedicel nearly 2.0 times longer than wide. Style about 5 times longer than postpedicel. Palpus pale.

Thorax almost wholly yellow. Scutum with 2 indistinct brownish spots near postalar calli, entirely tomentose. Postpronotal bristle hardly prominent. Dorsocentrals in multiple rows, complete posteriorly. Acrostichals 2-serial, complete posteriorly.

Legs with colour pattern: hind femur with brownish tinge in apical 3/4, otherwise legs yellow. Mid coxa with 2 brown bristles on outer side. Hind trochanter lacking spinules. Mid femur ( Fig. 36 ) slender, with 4 long yellow bristles in basal 1/2. Hind femur (viewed laterally) more or less evenly thickened, with row of anterodorsal bristles (5-6 subapical longer) and some prominent anterior and dorsal bristles in apical part. Fore tibia with ordinary setulae. Mid tibia lacking ventral spinules. Hind tibia with some longer ventral setulae, posterior apical comb unmodified.

Wing normally developed, covered with uniform microtrichia; with indistinct pattern, more or less evenly infuscate. Costal vein with short setulae along anterior margin. Vein R2+3 about 1.5 times longer than Rs. Distance between apices of R2+3 and R4+5 about 2 times longer than distance between apices of R1 and R2+3. R4+5 and M almost parallel and evenly arcuate in apical part. Halter with elongate, black knob and pale stem.

Abdomen lacking gland-like structures. Segments 1-2 largely pale yellow, remainder segments yellowish brown and stronger sclerotized. Segment 8 with 2 very long and several shorter bristles.

Hypopygium ( Fig. 37 ) brown, rather small. Hypandrium with 2 long bristles in apical part. Epandrium completely divided. Left epandrial lamella small, fused to hypandrium, lacking bristles in apical part. Left surstylus with upper lobe ( Fig. 38 ) divided; lower part slender, lacking surstylar comb, upper part subglobular, with 1 short bristle. Right surstylus ( Fig. 39 ) fairly large, rather elongate oval, with rounded apex, lacking spines. Left cercus unbranched, slender, short, lacking spines, with several bristles of different length in basal part. Right cercus consisting of two lobes, lacking spines; right lobe hardly prominent, with several marginal bristles of different length; left lobe short, broad, rounded at apex. Phallus short.

Female. In most respects identical to male. Terminalia shortened. Segment 8 normally sclerotized. Proximal margin of sternite 8 without 2 anteriorly directed rods. Apex of sternite 8 hinged and partially separated from base. Sternite 10 uniformly sclerotized, not fused with ventroapical margin of tergite 8. Cercus elongate oval, brownish yellow, clothed in setulae of different length.

Measurements. – Body length 1.4-1.7 mm, wing length 0.9- 1.2 mm.

Etymology. – “Taksin” (south in Thai) refers to south of Thailand where this species was found.

Phylogenetic relationships. – The relationships of S. taksin are unresolved beyond inclusion within the S. seeluang species group. However, the presence of 2 very long bristles on the segment 8 of the male abdomen, the general structure of the male terminalia and, especially, the greatly reduced cerci suggest this species is allied with S. laawae , S. crassinervis , and S. nhamyaaw .

Distribution and seasonal occurrence. – Thailand. Only known from one locality in South Thailand. The record is from October (end of rainy season in South Thailand).

Figures

Figs. 36-39. Stilpon taksin, new species, male. 36, mid leg, anterior view, 37, hypopygium, ventral view, 38, upper lobe of left surstylus, dorsal view, 39, right surstylus, dorsal view. Scale bar: 0.1 mm.