Borboroides acumen, 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: 209-211
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Borboroides acumen n.sp.
Material examined. HOLOTYPE.?, New South Wales: Kanangra-Boyd National Park , 1 km N of Boyd River [or Morong Creek] bridge, 1200 m, 4.x.2005, D.K.M. ( AM K219761). Near dead chook. Mounted on card point, with postabdomen in genitalia vial on same pin . PARATYPES. New South Wales: 3??, same data as holotype ( AM, ANIC); 1?, Mount Wilson [Blue Mountains; Waterfall Reserve, c. 900 m, 33°31'S 150°23'E], 2.ix.2002, D.K.M. ( AM) GoogleMaps .
Description (male, female unknown)
Very small blackish fly, agreeing with description of B. fimbria except as given below.
Coloration. Postfrons with entirely black ground-colour, not paler on anterior margin, with median subtriangular glossy zone in front of anterior ocellus extending c. halfway to ptilinal suture but with large area on each side of ocelli shining, with marked fingerprint sculpture and little pruinescence, not separated from median glossy zone by distinct pruinescent strip; anterior half of postfrons and region of fronto-orbital bristles largely thinly pruinescent, but with pruinescence not extending much mesad of orbital zone. Palpus tawny-brown. Thoracic pleura with pruinescence of similar extent to that of B. fimbria . Halter tawny, with yellow capitellum. Abdominal tergites 1 to 3 black with brown pruinescence; tergites 4 and 5 black with brown pruinescence on median zone, shining black on lateral zone; protandrial sclerite black with extensive brown pruinescence.
Head. Height of cheek c. 0.25–0.29 of height of eye; ocellar bristle slightly larger than posterior fronto-orbital.
Thorax. Intradorsocentral setulae in c. four irregular rows. Hind femur with preapical dorsal bristle and sometimes also smaller almost apical dorsal bristle; hind tibia with subapical spur, slightly shorter than maximum diameter of tibia. Wing: apical section of vein 4 3.4–3.7× as long as penultimate section.
Abdomen. Tergite 6 well sclerotized, undivided, narrowly transverse; protandrial complex approximately symmetrical; sternite 6 dorsally imperfectly fused with sternite 8, forming dark sclerotized band entirely encircling postabdomen, ventrally with pair of anterior prominences; ventral membrane behind sternite 6 pubescent, with pair of densely pubescent sclerotized plates; sternite 8 short and very stout, its ventral bridge with particularly long, dense pubescence; epandrium rather short, broadly pyriform, with extensive anteroventral bridge and posterodorsal median desclerotization; surstylus broadly spatulate, almost straight, slightly broadened at base, but without either basal lobe or foot; prehypandrial membrane with many rows of very short microtrichia; lateral process of hypandrium rather stout, its rounded, tumid apex with several setulae, one longer than others; distiphallus rather large and stout, its posterior surface smooth, convex, sclerotized and darkly pigmented, anterior surface of basal part rugose-scabrous, distal section abruptly flexed forward, somewhat membranous, partly finely rugose, with subapical gonopore; cerci very broad, basally approximated to each other and broadly articulated with epandrium, medial margins of pair closely parallel, distal margin of each produced into a subacute apex (appearing acuminate from some angles), medial part thick, incrassate, outer margin and apical parts thin, lamelliform; ejaculatory apodeme moderately small and slender.
Dimensions. Total length, 1.5–1.8 mm; length of thorax, 0.67–0.76 mm; length of wing, 1.7–1.9 mm.
Distribution. New South Wales: Central Tablelands district at altitudes of c. 900 m and over (few records).
In this species the texture-pattern of the postfrons resembles that of B. bulberti , but the subshining area lateral to the ocelli is larger, extending well in advance of anterior ocellus, and is almost devoid of pruinescence, though with strong fingerprint ridging, and the pruinescence around the fronto-orbital bristles forms a narrow zone, isolated on its medial side but not anteriorly. This condition approaches that of B. fimbria which, however, has the median and lateral non-pruinescent zones separated by a pruinescent strip. The hind tibial subapical spur of B. acumen is shorter than in B. fimbria , but not much longer than in B. bulberti ; this spur is much smaller in B. merzi .
Establishment of specific status for B. acumen depends mainly on the male postabdomen, including the shape of the surstylus and cercus. In contrast to that of B. bulberti and B. merzi , the distiphallus of B. acumen lacks the covering of dense filaments on both anterior and posterior surfaces.
The few specimens have been found near carrion (domestic fowl) and wombat dung baits.
The specific epithet is a Latin noun, sharpness, in reference to the sharp-edged lobe on the distal margin of the cercus.
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