Stilpon isaanensis, 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 : 322-323

Stilpon isaanensis , new species

( Figs. 15-19 )

Material examined. – Holotype - male, THAILAND: Loei province, Na Haeo , riverbanks in gallery forest at FIRS, sample n 2017, 23 May.2000, coll. P. Grootaert ( SWU).

Paratypes – Na Haeo, malaise trap at FIRS : 1 male, 22- 29.Oct.1999; 1 male, 42, 7-18.Dec.1999; 1 male, 12-28 Jun.2000; 1 female, 29.Apr-6 May.2001; 1 male, 12/61, 29- 5.Aug.2001, coll. Verapong Kiatsoonthorn & P. Grootaert (in coll. SWU, RBINS, ZRC). 1 male, 4 females, Khring Nam Tok, sample n 23041, 20 May.2003, coll. P. Grootaert; 1 male, 1 female, Malaise trap in bamboo wood at FIRS , 24 May.2003 (leg. P. Grootaert). (in coll. SWU, RBINS and ZRC) .

Diagnosis. – Species with yellow thorax. Fore tibia and tarsomere 1 brownish, postpronotal bristle long, scutal pattern indistinct, rows of acrostichal and dorsocentral bristles very short posteriorly.

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

Thorax almost wholly yellow. Scutum entirely tomentose, with 2 pale brownish, indistinct, posterolateral spots, including postalar calli which are deeper darkened; scutellum and postnotum with brownish posterior margin; pleural sutures (especially in darker specimens) brownish in varying extent. Postpronotal bristle long, brown, inclinate. Dorsocentral and acrostichal setulae very short on prescutellar depression.

Legs yellow with colour pattern: hind femur in apical 2/3, fore tibia (except extreme base), fore tarsomere 1, fore and mid tarsomeres 5 brownish (in darker specimens also mid femur somewhat brownish in apex); otherwise legs yellow. Hind trochanter with 2 brown spinules. Mid femur ( Fig. 15 ) slender, with 1 long anterior subapical bristle and row of 4 yellow, rather long, ventral bristles. 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 lacking prominent bristles. Mid tibia straight, slender, with hardly prominent ventral spinules. Hind tibia slightly arcuate, with ventral setulae more distinctly prominent.

Wing normally developed, covered with uniform microtrichia; almost uniformly infuscate, somewhat deeper along longitudinal veins. Costal vein with ordinary short setulae on anterior margin. Vein R2+3 about 2 times longer than Rs. Distance between apices of R2+3 and R4+5 nearly 2 times longer than distance between apices of R1 and R2+3. R4+5 and M almost parallel and slightly arcuate in apical part. Halter with contrast black elongate knob and pale yellow stem.

Abdomen yellowish, lacking gland-like structures, with segments 1-2 unmodified, bearing mostly scattered short setulae, segment 8 with moderately long bristles.

Hypopygium ( Fig. 16 ) dark brown, rather small. Hypandrium with 2 long bristles just beyond its middle. Epandrium completely divided. Left epandrial lamella small, fused to hypandrium, lacking bristles in apical part. Left surstylus ( Fig. 17, 18 ) with upper lobe divided; lower part lacking surstylar comb, upper part large, subglobular, with 1 short bristle. Right surstylus ( Fig. 19 ) large, hemispherical. Left cercus unbranched, digitiform, lacking spines, with 2 long and 1 shorter bristles in apical part. Right cercus undivided, short, subrectangular, lacking spines, with several short bristles. Phallus short.

Female. In most respects identical to male. Palpus brownish yellow. Hind trochanter lacking black spines. 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 refers to the Isaan region where the species was found.

Phylogenetic relationships. – The relationships of this species are unresolved beyond inclusion within the S. seeluang species group.

Distribution and seasonal occurrence. – Thailand. Known from one locality in the Loei province. Quite common with

records from the end of April to the beginning of August, October and December. Collected in bamboo wood and also from riverbanks in gallery forest.

Figures

Figs. 15-19. Stilpon isaanensis, new species, male. 15, mid leg, anterior view, 16, hypopygium, ventral view, 17, left surstylus, lateral view, 18, upper lobe of left surstylus, dorsal view, 19, right surstylus, dorsal view; u lb – upper lobe of left surstylus. Scale bar: 0.1 mm.