Borboroides parva, 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 : 187-190

Borboroides parva n.sp.

Figs 13, 14, 88–96

Material examined. HOLOTYPE.?, New South Wales: Putty Road , 41 km N of Colo River bridge, 33°11'S 150°41'E, c. 220 m [Yengo National Park], 31.v.2002, D.K.M. ( AM K219752 ). Mounted on card point . PARATYPES. New South Wales: 139??, 32!!, same locality as holotype, May, June, Sept. 2002 –2004, D.K.M. ( AM, ANIC, BM, BPB, CNC, MNHG, USNM); 22??, 16!!, Putty Road at Tinda Creek , 33°10'S 150°42'E, 31.v.2002, D.K.M. ( AM, AMST) .

Description (male, female). Minute, blackish, stout sphaerocerine-like fly.

Coloration. Head, thorax, legs and abdomen almost uniformly black to very dark brown. Postfrons entirely dull-pruinescent, usually with yellowish brown suffusion anteriorly; lower margin of cheek grey-pruinescent. Antenna blackish. Palpus dark grey-brown. Mesoscutum and scutellum grey-pruinescent; mesopleuron shining blackish centrally and anteroventrally, extensively grey-pruinescent anterodorsally and posterodorsally; sternopleuron largely subshining, with little pruinescence; pteropleuron and pleurotergite relatively densely grey-pruinescent. Legs almost uniformly dark brown; fore coxa tending to yellowish brown. Wing without markings; membrane tinged with smoky brown. Halter with yellowish brown pedicel and darker greyish brown capitellum. Abdominal tergites extensively grey- to brown-pruinescent.

Head higher than long; eye subcircular, with moderately sparse but obvious ommatrichia; postfrons broad and convex, with few, mostly erect anterior setulae; face slightly concave in profile, but with upper median part elevated, i.e. more distinctly carinate than in B. atra etc.; height of cheek 0.33–0.44 of height of eye; postvertical bristle moderately developed, smaller than in B. atra ; ocellar bristle large, but not potentially reaching ptilinal suture; posterior frontoorbital bristle reclinate and slightly sloped outwards; anterior fronto-orbital about as long as or slightly longer than posterior one, strongly directed outwards. Antenna more markedly porrect than in B. fimbria , B. atra etc.; segment 3 almost hemispherical, with doughnut-shaped proximal surface containing large central cavity, with both aristal insertion and sacculus remarkably close to basal rim; arista c. 1.6–2.0× as long as maximum diameter of eye, with numerous hairs/pubescence on whole length, those on distal half slightly longer than diameter of segment 5, those on basal part shorter. Prelabrum well sclerotized but not prominent, slightly but significantly larger in female than in male; palpus stout and moderately short; proboscis moderately small, but labella not particularly reduced.

Thorax stout; intradorsocentral setulae in four rows (two pairs) anteriorly and centrally; usually a pair of prescutellar acrostichal setulae scarcely larger than other setulae; scutellum without setulae; mesopleuron with few coarse posterior setulae; pteropleuron without setulae; the following thoracic bristles present: humeral, presutural, 1+1 notopleurals, postalar (displaced, mesad of postalar callus), 0+1 dorsocentrals; supra-alar and additional postsutural dorsocentral sometimes weakly differentiated; posterior intra-alar represented only by small setula; two unequal pairs of scutellars; one sternopleural. Fore femur with two to four posteroventral bristles and mostly shorter posterodorsal bristles; mid femur with one differentiated anterior bristle slightly beyond mid length; hind femur without differentiated bristles; fore and hind tibiae with some rather long setulae but no differentiated bristles or spurs; mid tibia with two large preapical dorsal bristles at slightly different levels, long apical ventral spur, and smaller apical anterior spur, otherwise without anterior bristles. Wing: costa with one well differentiated anterodorsal bristle just before humeral break (rarely duplicated or located just beyond humeral break); subcosta weakened opposite humeral break of costa, but sclerotized for short distance beyond break; anterior crossvein meeting vein 4 near or slightly basad of mid-length of discal cell; apical section of vein 4 c. 2.4–2.9× as long as penultimate section; basal crossvein oblique and aligned with strongly curved section of vein 5 bordering discal cell; apical section of vein 5 straight or almost so; anal crossvein and apical section of vein 6 absent.

Abdomen. Sternite 1 very short, sclerotized only at sides; tergite 5 slightly shorter than tergite 4 (both sexes). Male postabdomen: tergite 6 rather small, undivided; each spiracle 6 in membrane below lateral margin of tergite; spiracle 7 apparently absent; protandrial region posteriorly attenuated to form very short hypopygial petiole; sternite 6 reduced to long, darkly sclerotized strip on left side only, dorsally connected to sternite 8; sternite 7 distinct on left side, extending round ventral surface, weakly sclerotized; sternite 8 well sclerotized dorsally with two or three pairs of bristles or large setulae and no or few smaller setulae, with sclerotized ventral bridge anteriorly, and behind this with submarginal heavily sclerotized strip on each side terminating on posterior condyle; epandrium more elongate than in Heleomicra but less so than in other Borboroides spp. , with several stout setulae, and anteroventral bridge sclerotized but much attenuated; prehypandrial membrane smooth and glassy, without microtrichia; surstylus moderately elongate, articulated basally, with numerous microtrichia and few larger setulae on inner surface, with few microtrichia only on outer surface; hypandrium sclerotized anteriorly in front of aedeagal base, with lateral extension on each side articulating with epandrium but bearing no setulae; gonite long, curved, its apex posteriorly directed, with few small, mostly blunt setulae distally; basiphallus elongate, curved, with apex posteriorly directed; distiphallus small, membranous, largely recessed in subapical part of basiphallus; phallapodeme short, broadly bilaterally compressed, with no sclerotized connection to hypandrium; cerci joined by membranous proctiger for their full length, lacking ventral connecting sclerotized bar at bases and definite articulation with epandrium, each with fine microtrichia, few setulae, and one very long terminal bristle. Female postabdomen simple, tapered on c. posterior half; cerci somewhat elongate, free, with fine setulae of various lengths.

Dimensions. Total length,? 0.76–1.2 mm,! 1.0– 1.3 mm; length of thorax,? 0.33–0.50 mm,! 0.42–0.52 mm; length of wing,? 0.94–1.4 mm,! 1.2–1.5 mm.

Distribution. New South Wales: lowlands of Colo River district, between Blue Mountains and Hunter Valley. The known distribution is very restricted, including only two spot localities c. 3 km apart. This may change with wider use of the collection technique.

Notes

Borboroides parva shares some features with species of the atra group, notably the long, outwardly directed anterior fronto-orbital bristle, the presence of only one dorsocentral bristle, and the strongly bowed section of vein 5 bordering the discal cell; the dull, dark coloration and the distribution of pruinescence on the head and thorax are similar conditions to those of B. shippi of that group. It differs from the atra group in the longer arista and divided abdominal sternite 1, but the large costal bristle near the humeral break, the distally open anal cell, the single anterior bristle on the mid femur, the absence of any non-terminal anterior bristle on the mid-tibia, the relatively short protandrium, the continuous sclerotization of the hypandrial plate in front of the aedeagal base, and the unusual structure of the aedeagus are unique in the genus. Some of these conditions would have been considered to represent generic characters in pre-Hennigian taxonomy, but careful consideration suggests that the species is probably phylogenetically nested among the taxa of Borboroides , particularly those with the distinctive few dorsally directed mesopleural setulae and curved penultimate section of vein 5 ( staniochi , helenae , and atra groups). Its unique character states are interpreted as probable autapomorphies.

Borboroides parva is, on the average, the smallest insect in the genus, but there is size overlap with some species of the atra group.

All material was collected around wombat dung bait in an area with numerous wombat burrows.

The specific epithet is a Latin adjective—small.