Borboroides merzi, McAlpine, 2007

McAlpine, DK, 2007, Review of the Borboroidini or Wombat Flies (Diptera: Heteromyzidae), with Reconsideration of the Status of Families Heleomyzidae and Sphaeroceridae, and Descriptions of Femoral Gland-baskets, Records of the Australian Museum 59, pp. 143-219 : 206-209

Borboroides merzi n.sp.

Figs 140–145

Material examined. HOLOTYPE.?, Australian Capital Territory: Tidbinbilla Nature Reserve—Nature Trails , 35°27'S 148°53'E [given as “ 35.27S / 148.53E ” on label], 18.x.2002, B.M.—14 ( AM K219760 ). Double mounted on micro-pin through foam plastic . PARATYPES. Australian Capital Territory: 2??, 4!!, same data as holotype ( AM, MHNG); 1?, Blundells Creek , 30.ix.1987, D.H.C. ( ANIC) .

Other material (localities only given). New South Wales: Kanangra Road, 14.2 km S of Oberon–Jenolan road junction ( AM). Victoria: 13 miles [c. 21 km] W of Matlock ( AM); 11 km E of Warburton ( AM); near [northern foot of] Mount Juliet, 9 km E of Healesville ( AM, MV). Tasmania: Forest Road, Orford ( AM).

Description (male, female). Very small blackish fly, resembling B. fimbria and B. bulberti except in male postabdominal characters, agreeing with description of former species except as indicated below.

Coloration. Postfrons black to brown-black, anteriorly sometimes tinged with reddish brown, with extensive dark greyish pruinescence anteriorly and laterally, with broad irregularly triangular glossy zone around ocelli reaching c. half distance from anterior ocellus to ptilinal suture, without lateral glossy zones. Antennal segment 3 with variable tawny suffusion. Palpus yellow. Thoracic pleura with pruinescent zones approximately as given for B. fimbria . Abdominal tergites 1 to 5 of male entirely grey-brown pruinescent or almost so; in female tergites 5 and 6 each pruinescent on anterior part only.

Head. Height of cheek 0.28–0.34 of height of eye.

Thorax. As described for B. fimbria . Femora often with bristles less strongly developed than in B. fimbria but variable; hind tibia with or without preapical dorsal bristle, with subapical spur minute or undifferentiated. Wing: apical section of vein 4 2.6–3.6 times as long as penultimate section.

Abdomen. Male postabdomen almost symmetrical; tergite 6 reduced to pair of small weak lateral sclerites; sternite 6 approximately symmetrical and encircling postabdomen, with pair of prominent, shining, subconical ventral processes, which are encircled and medially separated by band of heavier cuticle; area immediately behind sternite 6 (probably partly representing sternite 7) sclerotized on each side, but asymmetrically so; sternite 8 stouter than in related species, less narrowed posteriorly, with few small dorsal setulae and pair of very prominent posterior condyles, tubular for substantial part of length though ventral sclerotization; epandrium very large and bulbous, broadly tumid anterodorsally (in dried specimens usually appearing pointed in this region through partial collapse along largely membranous median dorsal line), broadly attached to protandrium, with exceptionally large dorsal subcircular membranous foramen at junction, with large desclerotized posterior region near anus (above cerci), with scattered small dorsal setulae, and with well-developed anteroventral bridge occupying c. 0.25 of total length of epandrium; hollow internal sclerite attached to inner surface of epandrial margin on each side of prehypandrial membrane near point of attachment of lateral hypandrial sclerite to epandrium; prehypandrial membrane with numerous short microtrichia, many of which are arranged in short transverse comb-like groups; surstylus broad basally, deeply bilobed, with both lobes directed anteriorly, shorter anterobasal lobe with several rather large setulae, distal lobe elongate, with small to minute setulae and subapical gibbosity; lateral hypandrial sclerite complex, with prominent processes, outer process with several setulae including large apical one; between lateral hypandrial sclerite and aedeagus on each side, a subelliptic process, which is probably attached basally to basiphallus; distiphallus compact, with terminal gonopore, with many filamentous processes on anterior and distal surfaces, which, unless displaced (as in Fig. 144), are neatly packed to give the impression of parallel ridges; cerci broad and very short, connected by narrow sclerotized bridge, with moderately developed setulae and with slight minutely setulose anteromedial convexity. Female postabdomen: tergite 6 and sternite 6 separate, each undivided; cercus slightly but distinctly thickened and rounded apically.

Dimensions. Total length,? 1.2–1.3 mm,! 1.4–1.7 mm; length of thorax,? 0.54–0.63 mm,! 0.62–0.73 mm; length of wing,? 1.5–1.6 mm,! 1.7–1.8 mm.

Distribution. New South Wales: probably only cooler districts—few records. Australian Capital Territory: Canberra–Brindabella district. Victoria: areas east of Melbourne. Tasmania: east coast (single record).

Notes

Among species of the atra group with the capitellum of the halter yellow, B. merzi is distinguished by the single broad shining zone on the postfrons and vestigial or indistinguishable anteroventral subapical spur on the hind tibia; also, in the male, by the very large epandrium, broadly connected to the protandrium and bulging at the junction so as to project posteriorly in the reflexed position (this condition apparent in dried specimens), and by numerous details of epandrial and hypandrial structure; in the female by the undivided tergite 6 with shining posterior margin and the apically gibbous cercus.

Borboroides merzi has been collected in small numbers around wombat dung baits. The Tidbinbilla Reserve was stocked with numerous native mammals when the types were collected, but was largely destroyed by fire three months later.

The specific epithet refers to Bernhard Merz, who collected what is now type material and generously made it available.