Dolichopodinae

SCOTT E. BROOKS, 2005, Systematics and phylogeny of Dolichopodinae (Diptera: Dolichopodidae), Zootaxa 857, pp. 1-158 : 34-37

Genera of Dolichopodinae

Genus Allohercostomus Yang, Saigusa & Masunaga ( Fig. 5 A–E)

Allohercostomus Yang, Saigusa & Masunaga, 2001: 180 . Type species: Hercostomus rotundatus Yang & Saigusa [Palaearctic], by original designation.

Recognition. This genus may be recognized by its ventrally contiguous eyes, vertical setae shorter than postverticals, strong uniserial acrostichals, scutum flattened in front of scutellum, M straight and parallel or nearly parallel with R4+5 beyond crossvein dm­cu, and small size (body length 2.5–3.2 mm, wing length 2.8–3.4 mm).

Description. Head: Vertex not excavated, 1 pair of weak vertical setae, shorter than postverticals. Frons about 3.5–4.0 x wider than high, sides converging anteriorly. Face slightly narrowing below. Clypeus laterally detached from eye margin, recessed and narrowed below, subtriangular, lower margin rounded, ending well above lower eye margin. Palp small and narrow, somewhat digitiform. Antenna: scape short, subconical, with distinct medioventral process; pedicel short; first flagellomere about as long as wide, subtriangular to rounded apically; arista dorsal to subapical, 2­segmented, basal segment short, second segment bare. Eyes contiguous at lower margin. Postvertical setae stronger than uppermost pair of postoculars.

Thorax: Acrostichals uniserial and strong, posterior acrostichals as strong as anterior dorsocentrals; 6 dorsocentrals, fifth offset medially; 1 strong outer and 1 weak inner posthumeral; 2 notopleurals; 1 presutural; 1 sutural; 2 supraalars; 1 postalar. Upper part of propleuron with a few fine hairs; lower part of propleuron with 1 strong prothoracic seta; pleural surface in front of posterior spiracle bare; metepisternum bare (e.g., A. rotundatus ) or with 2 hairs (e.g., A. chinensis Yang, Saigusa & Masunaga ). Scutum with triangular, depressed region in front of scutellum. Scutellum with 1 strong inner seta and 1 minute outer seta on lateral margin.

Legs: Pulvilli developed normally on all legs. Foreleg: Tibia with anterodorsal row of strong setae and 1 long apicoventral seta (present in A. rotundatus ). Midleg: Femur with 1 anterior preapical seta. Hindleg: Coxa with strong lateral seta near middle; femur with 1 anterodorsal preapical seta; tibia of male with apical ridge­like process posterodorsally (present in A. rotundatus ); basitarsus equal to slightly longer than second tarsomere, with strong basiventral seta, slightly longer than width of basitarsus, male with weak dentiform process posterobasally (present in A. rotundatus ).

Wing: Hyaline to brownish. R2+3 more or less straight; R4+5 nearly straight with slight posterior curve in distal section; M straight, ending near wing apex, subparallel with R4+5; crossvein dm­cu distinctly shorter than distal section of CuA1.

Abdomen: Conical, short. Male: T6 bare; S2 and S3 unmodified, S4 weakly sclerotized, emarginate posteriorly; S5 mostly membranous, weakly sclerotized anterolaterally; S6 mostly membranous with thin sclerotized band along anterior margin, fused to T6 laterally; segment 7 forming well­developed peduncle; S8 subtriangular, setose. Hypopygium ( Fig. 5 A–C): Epandrium about 1.3–1.8 x longer than high; foramen positioned anterolaterally, well­separated from base of cerci; basiventral epandrial lobe moderately to welldeveloped, subquadrate in lateral view, basiventral epandrial seta present on lobe; apicoventral epandrial lobe well­developed, ovoid to elongate and digitiform, with 1 basiventral and 2 apical setae. Surstylus bilobed. Ventral lobe with dorsal hump beyond middle, distal portion narrow with thick apical spine. Dorsal lobe about as long as ventral lobe with strong dorsal seta beyond middle, apex acute. Postgonite with anteroventral portion weakly sclerotized; posterodorsal portion well­developed, simple, tapering apically. Proctiger brushes absent. Cercus subtriangular. Hypandrium well­developed, broad, extending to or beyond apex of apicoventral epandrial lobe, mainly free laterally, fused to epandrium distinctly anterior to basiventral epandrial lobe; hypandrial apodeme present, well­developed, hypandrial arms connected to hypandrium. Sperm pump weakly sclerotized; ejaculatory duct elongate; ejaculatory apodeme well­developed, laterally flattened; basal sclerite of sperm pump heavily sclerotized, U­shaped in dorsal view. Phallus slender ( A. rotundatus with preapical dentiform projection). Female ( Fig. 5 D,E): T6, T7, S6 and S7 undivided; T8 and S8 divided medially, tergite and sternite not fused anterolaterally. T10 divided medially into hemitergites each bearing 2–3 spines; spines rounded and flattened apically. Upper lobe of cercus with strong apical seta.

Geographical Distribution. Allohercostomus includes three species: A. rotundatus from Palaearctic China, A. chinensis from Oriental China, and A. nepalensis Yang, Saigusa & Masunaga from Nepal (Yang et al. 2001).

Phylogenetic Relationships. Allohercostomus is hypothesized to be the most basal dolichopodine based on the possession of a prescutellar depression (character 12:0), a plesiomorphy that is lost in the remaining dolichopodine genera. Autapomorphies of Allohercostomus include the possession of ventrally contiguous eyes, short vertical setae and strong uniserial acrostichals.

Remarks. The presence of a prescutellar depression was not mentioned in the original description of Allohercostomus . Although I have only seen specimens of A. rotundatus , the presence of this feature in the other species has been confirmed by D. Yang (pers. comm.).

Material Examined. Allohercostomus rotundatus (Yang & Saigusa) , [PA]: 2ɗ paratypes, 2Ψ paratypes ( SKU); 1ɗ paratype, 1Ψ paratype (LEM).

Figures

FIGURE 5. Allohercostomus rotundatus: (A) Male genitalia, left lateral view (external); (B) Male genitalia, left lateral view (internal); (C) Male genitalia, ventral view (postgonite, surstylus and cerci not shown); (D) Female genitalia, dorsal view; (E) Female genitalia, left lateral view.