Stilpon trilobatus, 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 : 335-336

Stilpon trilobatus , new species

( Figs. 64-68 )

Material examined. – Holotype - male, THAILAND: Dan Sai , along pond in village (between school and market), sample n 21038, 8 May.2000, coll. P. Grootaert ( SWU).

Paratypes – 1 male, Krabi, Huai waterfall, river banks, sample n 97113, 24.Oct.1997, coll. P. Grootaert ; 1 male, Songkhla province, Ban Khlong Kua , in old rubber plantation, sample n 97142, 29.Oct.1997, coll. P. Grootaert ); 2 males, 5 females, same data as in holotype ; 1 female, Na Haeo , in gallery forest along stream at FIRS, sample n 21035, 6 May.2001, coll. P. Grootaert. (in coll. SWU, RBINS & ZRC).

Diagnosis. – Species with black thorax and almost wholly brown hind femur. Male: mid femur slender, with a row of almost equally long ventral bristles, 1 or 2 black spines in apical third.

Description. – Male. Head black in ground-colour, with minute anterior ocellars, somewhat longer posterior ocellars and long inner verticals. Antenna and palpus light brown to brownish yellow. Postpedicel nearly 2.0 times longer than wide. Style about 5 times longer than postpedicel.

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: mid femur in apical 1/2, hind femur (except extreme base) and tarsomere 5 of all legs brownish; fore tibia, fore tarsomeres 1-4, hind coxa and hind tarsomere 1 brownish yellow; otherwise legs yellow. Mid coxa with 2 brown bristles on outer side. Hind trochanter lacking spinules. Mid femur ( Fig. 64 ) slender, with 2 anteroventral subapical bristles, 1 long yellowish bristle in extreme base, row of 7- 8 yellowish to brownish yellow long spine-like bristles before middle and 1 or 2 similar black spine-like bristles beyond middle of femur. Hind femur (viewed laterally) evenly thickened toward middle, with row of anterodorsal bristles becoming longer toward apex (4-5 subapical bristles scarcely longer than femur is deep) and row of prominent dorsal bristles. Fore tibia lacking prominent ventral bristles. Mid tibia with rows of ventral spinules and 1 longer subapical spinule. Hind tibia unmodified.

Wing normally developed, covered with uniform microtrichia; more or less uniformly and rather deep infuscate. Costal vein with ordinary short setulae on anterior margin. Vein R2+3 about 3.0 times longer than Rs. Distance between apices of R2+3 and R4+5 1.2-1.3 times longer than distance between apices of R1 and R2+3. R4+5 and M divergent and evenly arcuate in apical part. Halter with elongate, contrast knob and pale stem.

Abdomen largely yellowish brown, bearing mostly scattered dark setulae which are longer on pregenital segments, tergites 1-2 unmodified, tergite 3 narrowed. Gland-like structures

present between tergites 4-3 and 3-2 ( Fig. 82 ), with posterior space broader, consisting of three parts.

Hypopygium ( Fig. 65 ) brown, large. Hypandrium with 2 long 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. 66 ) undivided, with markedly developed surstylar comb. Right surstylus ( Fig. 68 ) moderately large, broadened in basal part, more or less rounded at apex, lacking spines. Left cercus ( Fig. 67 ) unbranched, slender, somewhat broadened at apex, very long, lacking spines, with 1 long ventral and 2 similar marginal bristles basally. Right cercus consisting of two lobes, lacking spines; left lobe slender, very long; right lobe slender, nearly 2 times shorter than left one. Phallus long, hair-like, curved.

Female. In most respects identical to male. Mid femur with row of yellowish bristles. Hind femur slender. Postabdomen elongate, strongly sclerotized, concolorous with thorax, tergite 8 distinctly separated from sternite 8. Proximal margin of sternite 8 without 2 anteriorly directed rods. Apex of sternite 8 not partially separated from base. Sternite 10 uniformly sclerotized, not fused with ventroapical margin of tergite 8. Cercus elongate oval, brownish, clothed in setulae of different length.

Measurements. – Body length 1.4-1.7 mm, wing length 0.9- 1.2 mm.

Etymology. – The name of this species refers to the trilobed posterior abdominal gland.

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

Distribution and seasonal occurrence. – Thailand. A species with a wide distribution: Northeast to South Thailand (Loei, Krabi and Songkhla provinces). Records in the North from May, October in the South.

Figures

Figs. 64-68. Stilpon trilobatus, new species, male. 64, mid leg, anterior view, 65, hypopygium, ventral view, 66, upper lobe of left surstylus, dorsal view, 67, left cercus and subepandrial sclerite, right lateral view, 68, right surstylus, dorsal view. Scale bar: 0.1 mm.

Figs. 80-84. Details of male abdomen, dorsal view. 80, Stilpon lek, new species, 81, Stilpon lekkwar, new species, 82, Stilpon trilobatus, new species, 83, Stilpon malayensis, new species, 84, Stilpon paradoxus, new species; T – tergite. Scale bar: 0.1 mm.