Helosciomyza subacuta, 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 : 63

Helosciomyza subacuta n.sp.

Fig. 18

Type material. Holotype ♂. Victoria: Wannon River, near Jimmy’s [Jimmy] Creek , Grampians , 10.xii.1977, D.K.M., M.A. S. ( MV). Double-mounted on micro-pin through polyporus, postabdomen in micro-vial on pin . Paratypes. Victoria: 4♂♂, 1♀ same data as holotype ( AM) ; 1♂, Reedy Creek , 5 km E of Cann River, June 1989, D.K.M. ( AM) .

Other material (doubtfully determined specimens). New South Wales: 1♂, Kunama [near Batlow], Aug. 1961, D.H.C. ( ANIC); 1♀, Boyd River crossing, Kanangra-Boyd National Park , April 2002, B.J.D., D.K.M. ( AM) .

Description (male, female). Somewhat resembling H. bickeli , H. steyskali etc.; agreeing with description of first species, except as indicated.

Coloration. Antennal segment 3 orange-tawny with rather extensive dorsal tawny-brown zone distad from about vicinity of aristal insertion to apex, not forming a sharply defined zone on medial surface. Mesopleuron with orange-tawny zone usually diffuse and indistinct. Fore femur, on posterior surface, tawny-yellow, with whitish pruinescence and generally no darker zones, except sometimes for a relatively small subapical grey-brown spot, on anterior surface with the usual distal brown zone but no basal or sub-basal brown zone; fore tarsus with segment 3 suffused with brown except at base; hind tibia with basal to sub-basal brownish zone. Wing: brown spot in subcostal cell absent or represented by slight yellow-brown suffusion; mark on anterior crossvein slight, that on discal crossvein obsolete.

Head. Height of cheek 0.36–0.39 of height of eye; scattered small setulae of cheek region usually not uniseriate anteriorly; face in profile usually less receding below than in related species.

Thorax. Pteropleuron and hypopleuron without setulae; proepimeral bristle absent or small.

Abdomen. Sternite 1 vestigial, without setulae. Male postabdomen: surstylus without posterior sub-basal tubercle or process, but shortly explanate on extreme base of posterior surface, with basal articular margin almost transverse in lateral view, with general outline slightly expanded distally or almost parallel-sided, postero-apically with short but acute prominence, distal margin in front of prominence narrowly inflexed.

Dimensions. Total length, ♂ 5.9–6.0 mm, ♀ 6.3 mm; length of thorax, ♂ 3.0– 3.3 mm, ♀ 3.2 mm; length of wing, ♂ 6.5–7.0 mm, ♀ 6.8 mm.

Distribution. Victoria: lowlands or near-lowlands in both east and west of state. New South Wales: only doubtfully determined specimens from central and southern highlands (see note below).

Notes

Together with Helosciomyza steyskali , typical populations of H. subacuta are distinguished from other species of the fuscinevris group by having the pteropleuron and abdominal sternite 1 without setulae, the infuscation on antennal segment 3 not very intense and more or less restricted to the dorsal half, and, apparently, no hypopleural setulae. The fore femur lacks any brown zone on the basal half, in contrast to H. steyskali , H. obliqua , and H. macalpinei . The shape of the surstylus is distinctive ( Fig. 18 ), as it is somewhat elongate, lacks a sub-basal posterior process, but has an acute, slightly distally inclined posterodistal angle. Segment 3 of the fore tarsus is less strongly browned distally than in H. steyskali , but, as the pigment fades slightly in old specimens, this character must be interpreted with care and the placement of females is difficult.

Two specimens listed above from localities in New South Wales are doubtfully referred to H. subacuta until their respective local populations are better known. The male from Kunama generally resembles specimens from Victoria but has hypopleural setulae, a condition otherwise only known for Australian Helosciomyza species in H. fuscinevris and H. bickeli , but this Kunama specimen lacks the setulae on sternite 1, normally present in those species; its surstylus is typical of H. subacuta in shape, but has setulae on the very slightly prominent posterobasal tubercle. The specimen from Boyd River is typical of H. subacuta in all features known for the female, but it is desirable that local males be examined for more decisive identification of the population.

The specific epithet is a Latin adjective, in reference to the subacute posterodistal angle of the surstylus.

Figures

Figures 14–18. (14) Neosciomyza peckorum (Boyd River), terminal part of epandrium and associated structures, anterior view, right anterior epandrial process cut away for clarity, scale = 0.5 mm. (15) Helosciomyza bickeli (Cobcroft Creek), left surstylus, outer view, scale = 0.2 mm. (16) H. fuscinevris (Clarence, near Lithgow), left surstylus, outer view. (17) same specimen, right surstylus, outer view. (18) H. subacuta (Wannon River), left surstylus, outer view. Figs 15–18 all same scale. aep, anterior epandrial process; bsp, basal surstylar process; c, cercus; ep, epandrium; ss, surstylus.