Borboroides petiolus, 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: 200-201
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Borboroides petiolus n.sp.
Material examined. HOLOTYPE.?, New South Wales: 10 km N of Colo Heights (i.e. from Upper Colo road junction), 9.ix.2005, D.K.M. ( AM K219757). Near old wombat carcass. Mounted on card point . PARATYPES. New South Wales: 6??, 4!!, same data as holotype, except some 12.ix.2005 ( AM, USNM) ; 3??, 1!, Goonoo State Forest , 5 mi. [c. 8 km] S of Mendooran, May 1970, G.D., G.A.H., D.K.M. ( AM, ANIC) ; 1?, Kandos, near Rylstone , June 1970, G.D. ( AM) ; 1?, Kanangra-Boyd National Park , 1 km N of Boyd River bridge, Oct. 2005 D.K.M. ( AM) ; 2??, Tantawangalo State Forest, near Candelo , May 1989, D.K.M. ( AM) .
Description (male, female). Very small largely blackish fly with unmarked wing, resembling B. fimbria except in male postabdominal characters and agreeing with description of that species except as indicated below.
Coloration. Head, thorax and abdominal tergites probably originally black, but faded to dark brown in older specimens. Postfrons broadly tawny-orange on anterior margin, with median glossy zone in front of anterior ocellus not as wide as distance between posterior ocelli and much narrower than lateral subshining zones, extending from anterior ocellus to c. 0.3 of distance to ptilinal suture. Mesopleuron with subshining, finely rugose and slightly pruinescent small central zone, with narrow posterior grey-pruinescent zone not narrowed ventrally, with little grey pruinescence on lower part of margin of fore coxal foramen only; sternopleuron with grey-pruinescent mark surrounding bristle; hypopleuron with posterior grey-pruinescent zone separated from glossy posterior margin. Tarsi tawny-yellow to brownish. Abdomen of female: tergite 4 largely glossy black with small median dark-pruinescent zone; tergite 5 glossy black with little pruinescence on anterior margin only; tergite 6 entirely greypruinescent. In male tergites 4 and 5 largely grey-pruinescent, with small bare lateral zones.
Head. Height of cheek 0.41–0.51 of height of eye. Prelabrum rather small, not very obviously sexually dimorphic.
Thorax. Chaetotaxy as in B. fimbria . Hind tibia with anteroventral subapical spur almost as long as greatest diameter of tibia.Wing: anterior crossvein meeting vein 4 near mid-length of discal cell; apical section of vein 4 c. 3.3–3.8× as long as penultimate section; basal crossvein somewhat oblique but forming distinct angle with penultimate section of vein 5, which is generally less strongly curved than in B. fimbria , B. atra and related species.
Abdomen. Male postabdomen: tergite 6 vestigial; compound protandrial sclerite apparently symmetrical, sternite 6 encircling postabdomen, without spur-like extensions; region of sternite 7 extensively sclerotized, not separated from sternite 6; sternite 8 forming petiole-like tube, much more elongate than in B. fimbria and related species and not expanded anteriorly, with pair of very prominent posterior condyles; epandrium very broadly subtriangular, nearly four times as wide as sternite 8 at mid length of latter, with anteroventral bridge well sclerotized but less extensive than in B. fimbria ; prehypandrial membrane with very short microtrichia on central and posterior parts mostly not in linear series; surstylus conspicuously large, subquadrate, broader than long, its distal margin much longer than basal margin, with group of many spine-like setulae inside distal margin, especially densely packed anteriorly, and separate very dense anterodistal patch of spinules, with setulae on outer surface few and minute; broad lateral process of hypandrium with compressedly clavate, long-hirsute anterior lobe and less prominent short-setulose posterior lobe; aedeagus slender (not studied in detail); cercus elongate, clavate, with many long setulae, especially on distal part, and with basal, anterolaterally extended gibbous foot bearing two or three setulae; transverse bridge connecting bases of cerci with a large setula in front of base of each cercus. Female postabdomen as given for B. fimbria .
Dimensions. Total length,? 1.6–1.8 mm,! 1.5–2.1 mm; length of thorax,? 0.73–0.93 mm,! 0.86–0.97 mm; length of wing,? 1.6–1.9 mm,! 2.1–2.2 mm.
Distribution. New South Wales: central and southern districts—scattered records.
Borboroides petiolus is a distinctive species of the atra group. It possesses a defined median glossy zone on the postfrons immediately in front of the anterior ocellus, unlike B. gorodkovi , B. corynetes , and B. shippi ; this zone is much smaller than in B. atra , B. fimbria and related species, but not as small as in B. menura . The pattern of pruinescence on the hypopleuron is distinct from these species, for, although it has a substantial grey-pruinescent posterior zone, this is well clear of the narrowly glossy posterior margin. Features of the male postabdomen are recognizable from those of all other species on whole dried specimens; these include the long, slender segment 8 contrasting with the very broadly subtriangular epandrium, the broadly subquadrate surstylus almost without setulae on its outer surface, and the clavate, widely separated cerci.
Borboroides petiolus has not been taken at wombat dung baits. The specimens I have collected were on or near carcasses (kangaroo, wombat, domestic fowl).
The specific epithet is a noun in botanical Latin, referring to the petiole-like segment 8 of the male abdomen.
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