Stilpon nhamyaaw, 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 : 324-326

Stilpon nhamyaaw , new species

( Figs. 25-29 )

Material examined. – Holotype - male, THAILAND: Ranong province, Ranong, rain forest, along stream, sample n 96028, 6 Apr.1996, coll. P. Grootaert (coll. RBINS).

Paratypes – 5 males, 2 females, same data as in holotype ( RBINS) .

Diagnosis. – Species with yellow thorax, resembles S. laawae differing from its by yellow fore tibia and tarsomere 1, wing

pattern consisting of two distinct brownish spots. Male: abdominal segment 8 with 2 very long bristles, left cercus with 3 very long spines in middle part.

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 entirely 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 brownish yellow in apical 3/4, otherwise legs yellow. Mid coxa with 2 brown bristles on outer side. Hind trochanter lacking spinules. Mid femur ( Fig. 25 ) 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 pattern consisting of 2 brownish, large, elongate oval spots separated more or less distinctly by pale basal half of vein M; remainder parts finely 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 1.5 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, contrast 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. 26 ) brown, small. Hypandrium with 2 long bristles in apical part. Epandrium completely divided. Left epandrial lamella small, fused to hypandrium, with 2 minute bristles in apical part. Left surstylus with upper lobe ( Fig. 27 ) divided; lower part elongate, lacking surstylar comb, upper part subglobular, with 1 short bristle. Right surstylus ( Fig. 29 ) fairly large, somewhat broadened toward apex, with more or less rounded upper margin. Left cercus ( Fig. 28 ) unbranched, hardly prominent, with 3 very long spines. Right cercus unbranched, hardly prominent, with several marginal bristles of different length. 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. – The name “nham” (spine in Thai) “yaaw” (long in Thai) refers to the long spines on the male left cercus.

Phylogenetic relationships. – The relationships of this species 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. Known from one locality in South Thailand. Recorded from the beginning of April in a rain forest.

Figures

Figs. 25-29. Stilpon nhamyaaw, new species, male. 25, mid leg, anterior view, 26, hypopygium, ventral view, 27, upper lobe of left surstylus, dorsal view, 28, left cercus and subepandrial sclerite, right lateral view, 29, right surstylus, dorsal view. Scale bar: 0.1 mm.