Stilpon monospinatus, 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 : 318-319

Stilpon monospinatus , new species

( Figs. 1-4 )

Material examined. – Holotype - male, THAILAND: Phang-Nga province , Khao Sok, river banks in rain forest, sample n 96035, 6 Apr.1996, coll. P. Grootaert (coll. RBINS).

Paratypes – 1 male, Phang-Nga, Khao Lak, Nangtong, beach forest, sample n 96046, 7 Apr.1996, coll. P. Grootaert (coll. RBINS) .

Diagnosis. – Species with black thorax. Male: mid femur with

3-4 yellow ventral bristles in basal 1/3, abdominal gland-like structures lacking, left surstylus without surstylar comb, left cercus with 1 short apical spine.

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

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

Legs yellow with colour pattern: fore tibia and fore tarsomere 1 entirely brownish yellow, hind femur brownish yellow in apical 1/2, mid femur with brownish tinge in apical part. Mid coxa with 2 brown bristles on outer side. Hind trochanter lacking spinules. Mid femur ( Fig. 1 ) slender, with 3-4 yellow long bristles in basal 1/3. Hind femur (viewed laterally) more or less evenly thickened, with row of short (shorter than femur is wide) anterodorsal bristles and row of prominent short dorsal bristles. Fore tibia with 1 dark erect bristle in apical part. Mid tibia with pale ventral spinules. Hind tibia 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 2.5 times longer than Rs. Distance between apices of R2+3 and R4+5 1.5 times longer than distance between apices of R1 and R2+3. R4+5 and M slightly divergent and evenly arcuate in apical part. Halter with elongate, contrastingly black knob and pale stem.

Abdomen largely dirty yellow, lacking gland-like structures, bearing mostly scattered dark setulae which are longer on pregenital segments, with all tergites (except segment 8) subequal in length, tergites 1-2 unmodified.

Hypopygium ( Fig. 2 ) brown. Hypandrium with 4 long bristles in apical part. Epandrium completely divided. Left epandrial lamella small, fused to hypandrium, with 1 short bristle in apical part. Left surstylus ( Fig. 3 ) with upper lobe divided; lower part rather small, subrectangular, with surstylar comb greatly reduced, upper part elongate, slender, with short apical spine. Right surstylus ( Fig. 4 ) large, with excision on upper margin, bearing numerous marginal bristles, lacking spines. Left cercus unbranched, narrow, elongate, somewhat broadened in apical part, with 1 short spine at apex, lacking long bristles in basal part. Right cercus unbranched, nearly as long as but almost 2 times broader than left cercus in middle part, more or less rounded at apex, lacking spines, with some short bristles on right margin. Phallus short.

Female. Unknown.

Measurements. – Body length 1.4-1.7 mm, wing length 0.9- 1.1 mm.

Etymology. – The name of this species refers to the single spine on the male left cercus.

Phylogenetic relationships. – The relationships of S. monospinatus are unclear beyond inclusion within the S. graminum species group, primarily due to the presence of an apical spine on the male left cercus.

Distribution and seasonal occurrence. – Thailand. Known from two localities of Phang-Nga Province. All records are from April. Collected on river banks in rain forest and in beach forest.

Figures

Figs. 1-4. Stilpon monospinatus, new species, male. 1, mid leg, anterior view, 2, hypopygium, ventral view, 3, left surstylus, lateral view, 4, right surstylus, dorsal view; ap spn – apical spine, cerc – cerci, l lb – lower lobe of left surstylus, lft epand lam – left epandrial lamella, m lb – medial lobe of left surstylus, rt epand lam – right epandrial lamella, rt sur – right surstylus, sur cm – surstylar comb, u lb – upper lobe of left surstylus. Scale bar: 0.1 mm.