Stilpon spinicercus, 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 : 319-320

Stilpon spinicercus , new species

( Figs. 5-10 )

Material examined. – Holotype - male, THAILAND: Chantaburi

Province, Lachamunkorn, in secondary rain forest, sample n 22003, 27 Mar.2002, coll. P. Grootaert (coll. RBINS).

Paratypes – Loei province, Na Haeo FIRS , Malaise trap: 1 male, 13-20 Mar.2000; 2 males, 15-21 Apr.2001; 2 males, 2 females, 29 Apr.2001; 1 male, 17-24 Jun.2001; 1 male, 24 Sep.-1 Oct.2001; 1 female, 2-4 Dec.2001; 2 males, 1 female, Na Haeo, 4 Feb.2001, coll. Verapong Kiatsoonthorn & P. Grootaert (in coll. SWU, ZRC & RBINS) .

Diagnosis. – Species with black thorax, most similar to S. monospinatus . Male: mid femur with black ventral spine just beyond middle, abdomen with gland-like structures between tergites 3-2 and 2-1, left cercus with 3 apical spines.

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

Thorax dark brown. Scutum entirely tomentose. Postpronotal bristle long, inclinate. Dorsocentrals in multiple rows, complete posteriorly. Acrostichals 2-serial, complete posteriorly.

Legs with colour pattern: hind femur brownish yellow in apical 2/3, fore tarsomere 5 brown, mid and hind tarsomere 5 brownish yellow; otherwise legs yellow. Mid coxa with 2 brown bristles on outer side. Hind trochanter lacking spinules. Mid femur ( Fig. 5 ) with 3 yellowish long bristles in extreme base, row of anteroventral brownish spinules before middle and 1 short black spine just beyond middle. Hind femur (viewed laterally) evenly thickened toward middle, with row of 8 fairly long anteroventral bristles in apical part and some prominent dorsal bristles in basal half. Fore tibia with 1 erect bristle in apical part. Mid tibia with hardly prominent spinules in apical part. Hind tibia unmodified.

Wing ( Fig. 6 ) 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, apex almost hyaline. Vein R2+3 about 2.0 times longer than Rs. Distance between apices of R2+3 and R4+5 subequal to distance between apices of R1 and R2+3. R4+5 and M divergent and evenly arcuate in apical part. Halter with contrast black elongate knob and pale stem.

Abdomen largely yellowish brown, bearing mostly scattered dark setulae which are longer on pregenital segments, with all tergites (except segment 8) of subequal in length, tergites 1-2 unmodified. Narrow gland-like structures present between tergites 3-2 and 2-1.

Hypopygium ( Fig. 7 ) brown. Hypandrium with 2 strong bristles in apical part. Epandrium completely divided. Left epandrial lamella small, fused to hypandrium, with 2 long bristles in apical part. Left surstylus with upper lobe ( Fig. 8 ) divided; lower part broadened, with markedly developed surstylar comb and 2 short apical spines, upper part elongate, slender. Right surstylus ( Fig. 10 ) large, subtriangular, divided into 2 lobes in apical part, bearing numerous strong marginal bristles; right lobe with 1 and left lobe with 2 spines, respectively. Left cercus ( Fig. 9 ) branched in apical part, lacking long marginal bristles in basal part, with right lobe bearing 3 long apical spines. Right cercus unbranched, short, subrectangular, lacking spines, bearing several short marginal bristles. Phallus short.

Female. In most respects identical to male. Mid femur with row of yellowish bristles. Abdomen lacking gland-like structures. Terminalia shortened. Segment 8 normally sclerotized. Proximal margin of sternite 8 without 2 anteriorly directed rods. Apex of sternite 8 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 1.6-1.9 mm, wing length 1.4- 1.7 mm.

Etymology. – The name of this species refers to the 3 spines on the male left cercus.

Phylogenetic relationships. – The relationships of S. spinicercus are unclear beyond inclusion within the S. graminum species group. The structure of the female terminalia and the upper lobe of the left surstylus may suggest closer relationships with the S. graminum (Fàllen) and its allies, though the structure of the right surstylus resembles that in S. nubilus Collin. S. spinicercus is the only species of this group which has the gland-like structures on the male abdomen.

Distribution and seasonal occurrence. – Thailand. Known from two areas: Loei and Chantaburi provinces. Records are almost from the whole year, except July, August, and most part of September.

Figures

Figs. 5-10. Stilpon spinicercus, new species, male. 5, mid leg, anterior view, 6, wing, dorsal view, 7, hypopygium, ventral view, 8, upper lobe of left surstylus, dorsal view, 9, left cercus, right lateral view, 10, right surstylus, dorsal view; sur cm – surstylar comb. Scale bar: 0.1 mm.