Helosciomyza obliqua, McAlpine, 2012

McAlpine, David K., 2012, Notes and Descriptions of Australian Helosciomyzidae or Comb-winged flies (Diptera: Schizophora), Records of the Australian Museum 64 (1), pp. 51-70 : 66-67

Helosciomyza obliqua n.sp.

Fig. 24

Type material. Holotype ♂. New South Wales : Boyd River [Morong Creek] crossing, Kanangra-Boyd National Park, 2–4.iv.2002, B.J.D., D.K.M. ( AM K263399 ); mounted on micro-pin through polyporus, postabdomen in micro-vial on main pin . Paratypes. New South Wales : 1♀, same data as holotype ( AM) ; 1♂, Wright’s Lookout , New England National Park, March 1961, D.K.M. ( AM) ; 1♂, Wentworth Falls , Blue Mountains, Jan. 1963, D.K.M. ( AM, erroneously determined as paratype of H. macalpinei by G. Steyskal). Victoria : 2♂♂, Mount Donna Buang , near summit, Warburton district, April 2003, B.J.D., D.K.M. ( AM, MV) .

Description (male, female). Resembling H. macalpinei and H. bickeli , agreeing with description of latter except as indicated below.

Coloration. Antennal segment 3 in large part dark brown to blackish (unfaded specimens), on outer lateral surface with ventrobasal tawny-orange zone, on medial surface with tawny-orange zone restricted to c. basal third. Mesopleuron with tawny-orange mark of very variable extent. Fore femur on anterior surface with extensive sub-basal brown zone, distally narrowly or incompletely separated from apical brown zone, on posterior surface largely mid-grey (colour resulting from pale grey pruinescence over darker brown cuticle), darker just before apex, or with posterior surface paler yellow grey with darker subapical zone, or, in one specimen with nebulous mid grey zone on basal half separated from distal grey zone by yellow-grey zone, approximately as in typical specimens of H. macalpinei ; fore tarsus with segment 3 dark brown on distal part.

Head. Cheek c. 0.28–0.37 as high as eye.

Thorax. Hypopleuron without setulae; proepimeral bristle present, minute, in all available males. Mid femur with comb of posteroventral setulae weakly developed; hind basitarsus lacking basal ventral cluster of short black setulae.

Abdomen. Sternite 1 much reduced, without setulae; sternite 5 of male with paired zones of dense, thick setulae broader than in H. bickeli and H. macalpinei , often more or less meeting on median line. Male postabdomen: epandrium with posterior margin broadly subangularly prominent above and behind articulation with surstylus; surstylus ( Fig. 24 ) with oblique basal articular margin, without sub-basal posterior process and noticeable excision of inner basal margin, almost parallel-sided beyond base, distal margin indistinctly toothed, oblique so as to be more prominent (though rounded) anterodistally (in contrast to H. subacuta ), not or very obtusely angular posterodistally.

Dimensions. Total length, ♂ —no available measurement (all males having abdomen dissected), ♀ 5.1 mm; length of thorax, ♂ 2.2–3.0 mm, ♀ 2.7 mm; length of wing, ♂ 5.4–6.6 mm, ♀ 5.8 mm.

Distribution. New South Wales and Victoria: cooler areas from New England National Park to Warburton district. Records few and scattered.

Notes

Among the species of the fuscinevris group with extensively darkened antennal segment 3, males of H. obliqua are most readily distinguished by the shape of the epandrium and surstylus (see details above and Fig. 24 ). Also H. obliqua generally has a proepimeral bristle or setula (often minute), which is usually absent in H. macalpinei but may be present or absent in H. australica . Coloration of the posterior surface of the fore femur is variable in H. obliqua , but the separate distinct posterodorsal dark grey mark generally present in H. macalpinei is usually less distinct or absent in H. obliqua ; on the often concealed anterior surface the extensive brown zone, extending near the base, contrasts particularly with the condition in H. australica , less so with that in H. macalpinei . Separation of the females of H. obliqua from those of related species is often a matter of uncertainty.

The specific epithet is a Latin adjective meaning oblique, in reference to the outline of the surstylus.

Figures

Figures 19–26.(19) Helosciomyza steyskali, protandrogram.(20) H.australica, epandrium and associated structures, posterior view, semi diagrammatic, setulae omitted. (21) H. neboissi (Pelion), left surstylus, outer view, scale = 0.2 mm. (22). H. australica (Picton Lakes), left surstylus, outer view. (23). H. steyskali (Boyd River), left surstylus, outer view. (24). H. obliqua (Mount Donna Buang), left surstylus, outer view. (25). H. driesseni (holotype), left surstylus, outer view. (26). H. macalpinei (holotype), left surstylus, outer view. Figs 21–26 all to same scale. c, cercus; ep, epandrium; pbf, posterobasal foot of surstylus; ss, surstylus; s5–s8, sternites 5 to 8; t5, t6, tergites 5 and 6.