Muscidideicus Becker

SCOTT E. BROOKS, 2005, Systematics and phylogeny of Dolichopodinae (Diptera: Dolichopodidae), Zootaxa 857, pp. 1-158 : 77-80

Genus Muscidideicus Becker

( Fig. 18 A–E)

Muscidideicus Becker, 1917: 268 . Type species Dolichopus praetextatus Haliday [Palaearctic], by original designation.

Muscideicus Parent, 1938: 265. Type species Dolichopus praetextatus Haliday , automatic. Unjustified emendation.

Recognition. This genus can be distinguished by the following combination of characters: abdomen dorsoventrally flattened, 7 dorsocentral setae, setation of mid and hind hind femora well­developed, nearly as strong as preapicals, R4+5 and M parallel and sinuous, upper and lower part of propleuron with long dense hair, prothoracic seta pale or brown.

Description. Head: Distinctly wider than high in frontal view. Vertex not excavated, 1 pair of strong vertical setae, stronger than postverticals. Frons about 2 x wider than high, sides converging anteriorly. Face and clypeus narrow in male, broad in female. Face concave in both sexes, concavity more pronounced in female; narrowest near middle in male, parallel sided in female. Clypeus weakly produced, lower margin straight, not reaching lower eye margin. Palp small, subtriangular, with weak setae on outer surface. Antenna: Scape short, subconical, with distinct acute medioventral process; pedicel short, with apical ring of fine setae; first flagellomere ovoid with subtriangular apex; arista short, dorsal, 2­segmented; distal segment bare. Lower postocular setae finer and slightly longer, postgenal area behind lower postoculars sometimes with dense setae. Postvertical setae stronger than uppermost pair of postoculars.

Thorax: Broad; acrostichals biserial; 7 dorsocentrals, sixth strongly offset medially; 1 strong outer posthumeral, 1 slightly weaker inner posthumeral, with adjacent row of 2–4 weaker setae; 2 notopleurals; 1 presutural; 1 sutural; 2 supraalars; 1 postalar. Upper and lower part of propleuron with a cluster of long dense hairs; lower part of propleuron with 1 strong, pale to brown prothoracic seta; pleural surface in front of posterior spiracle bare; metepisternum with 1–2 hairs. Scutellum with 1 strong inner seta and 1 weaker outer seta on lateral margin.

Legs: Pulvilli well­developed on all legs. Femora with well­developed surface setae, nearly as long as preapicals. Foreleg: Tarsus short, tarsomeres 2–5 subequal in length, male with dense pile ventrally. Midleg: Femur with 1–2 anterodorsal preapical setae; 1 distinct posterior preapical seta in addition to weak terminal posteroventral seta, sometimes weak. Hindleg: Coxa with strong lateral seta near middle; femur with strong setae dorsally, 1 anterodorsal preapical seta slightly stronger than surrounding setae; tibia of male with dentiform process posteroapically; basitarsus slightly shorter than second tarsomere, with a few weak to indistinct ventral setae, male with dentiform process posterobasally.

Wing: Hyaline, male with brown infuscation apically, venation somewhat pale. R2+3 nearly straight; distal portion of R4+5 and M of male subparallel with pronounced convex curve; R4+5 of female nearly straight with posterior bend in distal section; distal section of M beyond crossvein dm­cu of female with weak sinuous bend near middle, weakly convex beyond bend, weakly convergent with R4+5; M ending slightly before wing apex in both sexes; crossvein dm­cu distinctly shorter than distal section of CuA1.

Abdomen dorsoventrally flattened. Male: T6 bare; S2–3 unmodified; S4 widely emarginate posteriorly; S5 mostly membranous, weakly sclerotized laterally, with narrow sclerite posteromedially; S6 mostly membranous, weakly sclerotized at anterior margin; segment 7 forming well­developed peduncle; S8 subtriangular, setose. Hypopygium ( Fig. 18 A–C) large. Epandrium longer than high, with strong dorsolateral bulge in apical half; foramen positioned laterally just before middle, well­separated from base of cerci; basiventral epandrial lobe weakly developed, with weak basiventral epandrial seta; apicoventral epandrial lobe well­developed, elongate, projecting laterally and bent dorsally, with 3 setae on apical half. Surstylus bilobed. Ventral lobe large and bulbous, with thick, digitiform process apically and a pair of rounded projections dorsally. Dorsal lobe longer than ventral lobe; wide, laterally flattened, with dorsal projection bearing a pair of thick curved setae. Postgonite with weakly sclerotized anteroventral portion; posterodorsal portion not developed ( Fig. 18 B). Proctiger brushes absent. Cercus subquadrate. Hypandrium more or less symmetrical in ventral view, apex pointed, base broad with narrow medial sclerite, free, not fused to epandrium laterally or basally; hypandrial apodeme present, well­developed; hypandrial arms connected to hypandrium. Sperm pump cylindrical; ejaculatory apodeme rod­like; basal sclerite of sperm pump heavily sclerotized, broadly Vshaped in dorsal view. Phallus slender with dentiform process at distal third. Female ( Fig. 18 D,E): T6, T7, S6 and S7 undivided; T8 and S8 divided medially, tergite and sternite fused anterolaterally forming a narrow sclerite ( Fig. 18 E). Furca present. T10 divided medially into hemitergites each bearing 5–7 spines, medial spines flattened and rounded apically. Upper lobe of cercus lacking strong apical seta.

Geographical Distribution. This monotypic genus is restricted to the western Palaearctic region ( Negrobov 1991).

Phylogenetic Relationships. Muscidideicus is the basal genus of the Ortochile genus group and forms the sister taxon to the large clade including Sybistroma , Hercostomus , Ortochile , Poecilobothrus and Parahercostomus . Autapomorphies of Muscidideicus include the possession of seven pairs of dorsocentral setae and a dorsoventrally flattened abdomen.

Remarks. Although Becker (1917) referred to Muscidideicus as a genus on pages 124, 125 and 224, he clearly indicated on pages 268–269 that he regarded it as a subgenus of Hercostomus , and that classification was subsequently followed by Dyte (1969, 1976) and d’Assis Fonseca (1978). In contrast, Stackelberg (1930) and Negrobov (1980, 1991) treated Muscidideicus as a genus. The latter classification is supported by the cladistic analysis.

Material Examined. Muscidideicus praetextatus (Haliday) , [PA]: 2ɗ, 2Ψ ( MNHN); 2ɗ (LEM).

Figures

FIGURE 18. Muscidideicus praetextatus: (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.