Gymnopternus Loew

SCOTT E. BROOKS, 2005, Systematics and phylogeny of Dolichopodinae (Diptera: Dolichopodidae), Zootaxa 857, pp. 1-158 : 60-63

Genus Gymnopternus Loew

( Fig. 13 A–F)

Gymnopternus Loew, 1857: 10 . Type species: Dolichopus cupreus Fallén [Palaearctic], designation by Coquillett, 1910: 548. Listed as a subgenus ( Pollet 1990; Chandler 1998) or synonym of Hercostomus ( Dyte 1975, 1976; Dyte & Smith 1980; Negrobov 1991; Poole 1996).

Paragymnopternus Bigot, 1888a : xxiv [1888c: xxiv; 1890: 281]. Type species: Dolichopus cupreus Fallén [Palaearctic], designation by Evenhuis & Pont, 2004: 46. Junior objective synonym of Gymnopternus Loew, 1857 , synonymized by Evenhuis & Pont, 2004: 46.

Recognition. This genus is distinguished by its nearly straight wing vein M, R4+5 and M parallel to subparallel, pleuron with a cluster of fine hairs in front of the posterior spiracle, fore tibia usually with an anterodorsal comb­like row of strong, often spine­like setae. Gymnopternus is most similar to New Genus A, but can be distinguished by characters given in the “Recognition” section for New Genus A and in the key.

Description. Head: Vertex not excavated, 1 pair of strong vertical setae, stronger than postverticals. Frons about 1.8–3.0 x wider than high, sides subparallel to slightly convergent anteriorly, bare or with 1–3 fine hairs in front of each vertical seta (e.g., G. annulatus Van Duzee , G. barbatulus Loew , G. ohioensis Robinson , G. propriofacies Robinson ). Face concave, bare or with a few weak hairs, broad to narrow in male, sides strongly to weakly convergent below, narrowest at or above upper clypeal margin, usually broader in female with sides convergent to subparallel. Clypeus pubescent or bare, flat to weakly produced, sometimes strongly produced in female, lower margin straight or slightly emarginate, ending well above lower eye margin. Palp ovoid, rounded to subtriangular apically, with weak setae on apical half of outer surface, usually with distinct apical seta. Antenna: Scape subconical, with distinct acute medioventral process; pedicel short, medial margin occasionally strongly projecting into first flagellomere; first flagellomere variable, subquadrate, ovoid or subtriangular to triangular, sometimes acute and elongate in male (e.g., G. subulatus Loew ), about as long as wide to over 2 x longer than wide, usually more well­developed and elongate in male; arista dorsal, 2­segmented, second segment pubescent, nearly plumose in some species, occasionally bare with apical lamella in male (e.g., G. nigribarbis Loew , G. mirificus Melander ). Lowermost postocular seta occasionally stronger. Postvertical setae slightly to distinctly stronger than uppermost pair of postoculars.

Thorax: Acrostichals biserial; usually with 6 dorsocentrals, occasionally with 5 (e.g., G. f l a v u s Loew), penultimate pair strongly offset medially, posterior part of mesonotum in front of scutellum bare or with fine setae; 1 strong outer posthumeral, 1 weaker inner posthumeral, sometimes indistinct; 2 notopleurals; 1 presutural; 1 sutural; 2 supraalars; 1 postalar. Upper part of propleuron with fine hairs, outer 2–3 hairs sometimes slightly stronger; lower part of propleuron with 1 strong prothoracic seta and fine hairs; pleural surface in front of posterior spiracle with at least 1 fine hair, usually with a cluster of 2–10 fine hairs; metepisternum with 1 or more fine hairs. Scutellum with 1 strong inner seta and 1 minute outer seta on lateral margin, dorsal surface and margin bare or with fine hairs.

Legs: Pulvilli developed normally on all legs, occasionally slightly enlarged on fore tarsus of male (e.g., G. exilis Loew and G. subdilatatus Loew ). Foreleg: Tibia usually with distinct anterodorsal comb­like row of strong, often spine­like setae, usually preceded by 1 strong anterodorsal seta; males of some species (e.g., G. barbatulus , G. o h i o e n s i s, G. p ro p ­ riofacies) with fine ventral hairs on tarsomeres 2–5. Midleg: Femur with 1 anterior preapical seta, some species with 1 strong posteroventral preapical in addition to terminal posteroventral preapical, which is also sometimes developed (e.g., G. annulatus , G. barbatulus , G. o h i o e n s i s, G. propriofacies ). Hindleg: Coxa with strong lateral seta near middle; femur with 1 anterodorsal preapical seta; tibia sometimes with apical, ridge­like or dentiform process posterodorsally in male; basitarsus shorter than second tarsomere, most species with distinct basiventral seta, males of most species with distinct dentiform process and/or sclerotized ridge posterobasally.

Wing: Brownish to hyaline. Costa of male occasionally swollen basally before R1 (e.g., G. brevicornis (Staeger) , G. c e l e r (Meigen)); R2+3 straight to weakly convex; R4+5 nearly straight or with slight posterior curve in distal section, usually straightening just before apex; distal section of M beyond crossvein dm­cu usually with barely discernable sinuous bend before middle, nearly straight, or with slight posterior curve in distal section similar to that of R4+5, ending near wing apex; R4+5 and M parallel to subparallel; crossvein dm­cu shorter than distal section of CuA1.

Abdomen: Subconical. Male: T6 bare; S2 unmodified or weakly emarginate and membranous anteriorly and posteriorly; S3 weakly to strongly emarginate and membranous posteriorly; S4 strongly emarginate and membranous posteriorly to entirely divided medially; S5 mainly membranous with weakly sclerotized regions, often with weakly sclerotized lateral longitudinal bands, distal portion sometimes with narrow medial sclerotization, pair of eversible of glands often present (e.g., G. aerosus (Fallén) , G. a s s i m i ­ lus (Staeger), G. cupreus , G. metallicus (Stannius) , see Couturier (1974)); S6 mainly membranous, weakly sclerotized along anterior and/or lateral margin; segment 7 forming welldeveloped peduncle; S8 heart­shaped, often with short, narrow stalk­like base, setose. Hypopygium ( Fig. 13 A–D) large, nearly as large as abdomen in some species. Epandrium 1.5–1.8 x longer than high, ovoid in lateral view; foramen positioned anterolaterally, wellseparated from base of cerci; basiventral epandrial lobe absent to moderately developed, basiventral epandrial seta usually present, occasionally absent (e.g., G. annulatus , G. barbatulus ); apicoventral epandrial lobe well­developed, short and broad to elongate and slen­ der, enlarged apically, with 1 strong lateral to lateroventral seta near or slightly beyond middle, 2 smaller preapical to apical setae, occasionally with a cluster of apical setae (e.g., G. weemsi Robinson ). Surstylus bilobed. Ventral lobe variable, more or less digitiform, often with dorsal projections, apex usually tapered bearing a stout seta. Dorsal lobe laterally flattened, apex rounded to acute upcurved, often rugose laterally, usually with 1 strong dorsal to apical seta often on a tubercle, subequal to slightly longer than ventral lobe. Postgonite ( Fig. 13 B,C) with anteroventral portion usually very reduced to absent, occasionally developed, weakly sclerotized, flat, broad and emarginate anteriorly; posterodorsal portion well­developed and complex, usually broad, with ventral medial lobe and a pair of dorsolateral lobes, often with secondary dorsal and lateral membranous lobes, ventral medial lobe occasionally absent. Proctiger brushes absent. Cercus small to medium­sized, occasionally large, variable in shape ranging from subtriangular to ovoid to subrectangular to crescent­shaped, occasionally bilobate ( G. exilis ). Hypandrium simple, narrow, troughlike, mainly free laterally, fused to epandrium distinctly anterior to basiventral epandrial lobe/seta ( Fig. 13 D); hypandrial apodeme present, well­developed; hypandrial arms connected to hypandrium, sometimes also narrowly fused to epandrium laterally near basiventral epandrial seta/lobe. Sperm pump large, reniform; ejaculatory apodeme elongate, curved ventrally with acute apex, distinctly flattened laterally to rod­like, often weakly sclerotized and translucent, usually with long basal projections appressed to base of phallus ( Fig. 13 B), projections occasionally short (e.g., G. petilus Yang & Saigusa ); basal sclerite of sperm pump variably sclerotized, nearly straight in dorsal view with lateral triangular projections. Phallus elongate and slender, apex weakly serrate and/or with dentiform process. Female ( Fig. 13 E,F): T6, T7, S6 and S7 undivided, T6 and T7 often with darkened proximal and lateral margins; T8 and S8 divided medially, tergite and sternite weakly fused anterolaterally. T10 divided medially into hemitergites each bearing 4 spines along outer margin, spines rounded and flattened apically. Upper lobe of cercus usually with long apical seta, seta occasionally reduced (e.g., G. barbatulatus )

Geographical Distribution. This genus is widespead and occurs in the Nearctic, Palaearctic and Oriental regions.

Phylogenetic Relationships. Gymnopternus forms the sister group to the Dolichopus + New Genus A clade based on the possession of a cluster of setae in front of the posterior spiracle. As discussed above (see “ Dolichopus genus group”), Gymnopternus should be regarded as a genus and not placed in Hercostomus as a synonym or subgenus, as has been done by most Palaearctic workers.

Remarks. Most species of Gymnopternus have a distinctive anterodorsal row of strong setae on the fore tibia. A similar modification has also arisen in some members of the Hercostomus longiventris lineage (e.g., H. fulvicaudis , H. tibialis ), Hercostomus nigriplantis (Stannius) , Allohercostomus rotundatus , Poecilobothrus aberrans , and outside the Dolichopodinae in Colobocerus alchymicus .

Material Examined. Gymnopternus aerosus (Fallén) , [PA, OR]: 5ɗ, 4Ψ ( CNC); 5ɗ, 3Ψ (LEM); Gymnopternus annulatus Van Duzee , [NE]: 2ɗ ( CNC); Gymnopternus barbatulus Loew , [NE]: 8ɗ, 4Ψ ( CNC); Gymnopternus brevicornis (Staeger) , [PA]: 3ɗ, 3Ψ (LEM); 3ɗ, 1Ψ ( CNC); Gymnopternus celer (Meigen) , [PA]: 3ɗ, 3Ψ (LEM); 2ɗ ( CNC); Gymnopternus congruens (Becker) , [OR]: 6ɗ, 4Ψ ( CNC); 2ɗ, 1Ψ (LEM); Gymnopternus crassicauda Loew , [NE]: 3ɗ, 2Ψ ( CNC); Gymnopternus cupreus (Fallén) , [PA]: 1ɗ ( CNC); 4 ɗ, 1Ψ (LEM); Gymnopternus debilis Loew , [NE]: 3ɗ, 2Ψ ( CNC); Gymnopternus exilis Loew , [NE]: 9ɗ, 2Ψ ( CNC); Gymnopternus flavus Loew , [NE]: 5ɗ, 3Ψ ( CNC); Gymnopternus frequens Loew , [NE]: 11ɗ, 5Ψ ( CNC); Gymnopternus humilus Loew , [NE]: 12ɗ, 3Ψ ( CNC); Gymnopternus lividifrons Van Duzee , [NE]: 2ɗ, 1Ψ ( CNC); Gymnopternus nigribarbis Loew , [NE]: 8ɗ, 3Ψ ( CNC); Gymnopternus ohioensis Robinson , [NE]: 2ɗ ( CAS); Gymnopternus opacus Loew , [NE]: 6ɗ, 3Ψ ( CNC); Gymnopternus petilus Yang & Saigusa , [PA]: 1ɗ paratype, 1Ψ paratype ( ISNB); Gymnopternus propriofacies Robinson , [NE]: 5ɗ ( CAS); Gymnopternus scotias Loew , [NE]: 1ɗ, 1Ψ ( CNC); Gymnopternus silvestris Pollet , [PA]: 2ɗ, 2Ψ (LEM); Gymnopternus spectabilis Loew , [NE]: 7ɗ, 7Ψ ( CNC); Gymnopternus subdilatatus Loew , [NE]: 6ɗ, 3Ψ ( CNC); Gymnopternus subulatus Loew , [NE]: 7ɗ, 6Ψ ( CNC); Gymnopternus vockerothi Robinson , [NE]: 6ɗ, 4Ψ ( CNC); Gymnopternus weemsi Robinson , [NE]: 2ɗ ( CAS).

Figures

FIGURE 13. Gymnopternus cupreus and G. a e ro s u s: (A) G. cupreus, male genitalia, left lateral view (external); (B) G. cupreus, male genitalia, left lateral view (internal); (C) G. cupreus, male genitalia, postgonite and subepandrial sclerite / hypandrial arm complex, lateral view; (D) G. cupreus, male genitalia, ventral view (postgonite, surstylus and cerci not shown); (E) G. a e ro s u s, female genitalia, dorsal view; (F) G. ae ro s us, female genitalia, left lateral view.