Stilpon Loew, 1859

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 : 316

Stilpon Loew, 1859

Agatachys Meigen, 1830 . Nomen nudum. Cited as a MS name of Winthem in specific synonymy under Tachydromia celeripes Meigen (= graminum Fallén, 1915 ).

Stilpon Loew, 1859 . Subgenus of Drapetis Meigen. Type species: Tachydromia graminum Fallén, 1815 (des. by Loew, 1864).

Tetraneurella Dahl, 1909 . Type species: Tetraneurella beckeri Dahl, 1909 (mon.) (= graminum Fallén, 1915 ).

Pseudostilpon Séguy, 1950 . Type species: Tachydromia paludosa Perris, 1852 (orig. des.).

Diagnosis. – Very small flies, 1.0- 2.5 mm long. Male. Head dark brown to black in ground-colour. Eyes with ommatrichia, contiguous in facial part. Ommatidia slightly enlarged below antennae. Frons linear to sublinear, narrow to fairly wide, entirely or partially tomentose. Face strongly convex. Gena barely extended below eye. Ocellar tubercle with 2 pairs of bristles. One pair of prominent inclinate vertical bristles. Antennae placed below or near middle of head; scape small; pedicel large and globose, with long ventral preapical bristle; postpedicel small, ovate, with well prominent dorsoapical extension; stylus dorsoapical, long. Palpus elongate-ovate, with distinct apical seta. Proboscis slightly recurved.

Thorax black brown to yellow in ground-colour. Scutum not shiny and entirely tomentose or partly or entirely shiny and lacking tomentum. Postpronotal lobe undifferentiated. Postalar callus partially differentiated. Thoracic bristles mostly hardly prominent; acrostichals arranged in 2 complete or incomplete rows posteriorly or absent; dorsocentrals in 2 or more rows, often undifferentiated from intra-alar setulae, complete or incomplete posteriorly. Mesopleuron largely shiny, tomentose along dorsal margin. Metaepimeron large. Halter with knob yellow to black, rarely absent.

Wing normally developed or sometimes shortened, broad or narrow; hyaline, more or less infuscate or with distinct pattern. Microtrichia uniform or lengthened in some parts of wing. Costal setae short or long. Rs originating halfway along R1. R2+3 complete or incomplete. Cell br short, distinctly less than length of cell bm. Crossvein bm-cu nearly transverse. A1 and crossvein CuA2 absent.

Legs short, often with distinct colour pattern. Fore femur thickened. Mid femur slender to barely thickened, usually armed with bristles and spinules or spines arranged in specific patterns. Hind femur evenly thickened or constricted near middle, with well prominent anterodorsal bristles. Fore tibia more or less spindle-like, usually lacking prominent bristles; Mid tibia often armed with ventral spinules; hind tibia slender, lacking prominent bristles, rarely with modified posterior apical comb. Tarsi unmodified, except slightly to moderately expanded basitarsus.

Abdomen with segments 1-7 lightly sclerotized, subequal in length or some segments shortened, rarely segments 1-2 modified; segment 8 always short, partially concealed by segment 7; squamiform lateral setae absent. Gland-like intersegmental structures present or absent.

Hypopygium asymmetrical, rotated 90 to the right. Epandrium completely divided. Left epandrial lamella small and fused to hypandrium, with long or greatly reduced to absent bristles in apical part. Left surstylus divided into 3 (or 4) lobes; upper lobe with or without surstylar comb. Right epandrial lamella usually large, positioned ventrally. Right surstylus large to moderately large, undivided, sometimes with apical spines. Cerci, including subepandrial sclerite, fused together basally, rarely fused completely into one large lobe, sometimes greatly reduced. Left cercus usually large, with or without apical spines. Right cercus undivided or divided, sometimes with apical spines. Phallus elongate, well sclerotized, hair-like or, rarely, straight or very short and rather weakly sclerotized; single rod-shaped ejaculatory apodeme present.

Female. Similar to male except ordinary setation on mid legs, unmodified hind femur, wing microtrichia and abdominal segments 1-2. Abdomen without gland-like structures. Terminalia short to elongate. Tergite 8 not fused laterally with sternite 8. Sternite 8 entire, or with apex hinged and partly or completely separated from base. Tergite 9 absent. Sternite 9 reduced to small internal sclerite. Tergite 10 absent. Sternite 10 plate-like or desclerotized medially, positioned below proctiger. Cercus elongate-ovate or broad-ovate. Spermatheca membranous, sac-like.