Stilpon laawae, 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 : 323-324

Stilpon laawae , new species

( Figs. 20-24 )

Material examined. – Holotype - male, THAILAND: Nakhon Nayok, Chulachomkla , along brook in shade, sample n 97163, 12 Nov.1997, coll. P. Grootaert (coll. RBINS).

Paratypes – 1 male, same locality as holotype. Loei province, Na Haeo FIRS in Malaise trap, 3-10 Sep.1999, coll. P. Grootaert ; 1 female, coll. Verapong Kiatsoonthorn & P. Grootaert; 1 male, Na Haeo, Chang Tok waterfall, sample n 23035, 17 May.2003, coll. P. Grootaert (in coll. SWU & RBINS).

Diagnosis. – Species with yellow thorax, most similar to S. isaanensis differing from it in having quite long acrostichal and dorsocentral bristles throughout, hardly prominent postpronotal bristle and very short left cercus male terminalia.

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

Thorax almost wholly yellow. Scutum entirely tomentose, scutal spots almost invisible, postpronotal calli dark. Postpronotal bristle hardly prominent. Dorsocentrals in multiple rows. Acrostichals 2-serial.

Legs yellow, with colour pattern: fore tibia (except base) and fore tarsomere 1 brown; otherwise legs yellow. Hind trochanter lacking spinules. Mid femur ( Fig. 20 ) slender, with 4 long yellowish bristles in basal part. Hind femur (viewed laterally) evenly thickened toward middle, with 1 row of anteroventral bristles becoming longer toward apex of femur (3 subapical bristles longest) and some hardly prominent dorsal bristles in basal part. Fore tibia greatly incrassate, lacking prominent ventral bristles. Mid tibia lacking prominent ventral spinules. Hind tibia unmodified.

Wing ( Fig. 21 ) normally developed, covered with uniform microtrichia, finely infuscate. Costal vein with ordinary short setulae on anterior margin. Distance between apices of veins R2+3 and R4+5 about 2.0 times longer than distance between apices of veins R1 and R2+3. R4+5 and M slightly divergent and evenly arcuate in apical part. Halter with contrast black, elongate knob and pale yellow stem.

Abdomen largely brownish yellow, lacking gland-like structures, with segments 1-2 unmodified, bearing mostly scattered short setulae; tergites 1-2 yellowish, segment 8 with 2 very long and several shorter bristles.

Hypopygium ( Fig. 22 ) pale brown, small. Hypandrium with 2 long bristles in apical part. Epandrium completely divided. Left epandrial lamella small, fused to hypandrium, with 1 minute bristle in apical part. Left surstylus with upper lobe ( Fig. 23 ) divided; lower part elongate, lacking surstylar comb, upper part moderately large, subglobular, with 1 short bristle. Right surstylus ( Fig. 24 ) large, rather elongate oval, lacking spines. Left cercus unbranched, short, slender, lacking spines, with 1 long bristle in apical part. Right cercus consisting of two lobes, lacking spines; left lobe short, broad, with several bristles basally; right lobe hardly prominent, rounded. Phallus short.

Female. In most respects identical to male. Palpus brownish yellow. 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. – This species is dedicated to Dr. La-aw Ampornpan from Srinakharinwirot University who stimulated our studies of the Thai fauna.

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. crassinervis , S. nhamyaaw , and S. taksin .

Distribution and seasonal occurrence. – Thailand. Known from two localities, respectively in Central and Northeast Thailand. Records from the beginning of September to the beginning of October.

Figures

Figs. 20-24. Stilpon laawae, new species, male. 20, mid leg, anterior view, 21, wing, dorsal view, 22, hypopygium, ventral view, 23, upper lobe of left surstylus, dorsal view, 24, right surstylus, dorsal view. Scale bar: 0.1 mm.