Bama (Bama) aurantium, McAlpine, 2015

McAlpine, David K., 2015, Signal Flies of the Genus Bama (Diptera: Platystomatidae) in Papua New Guinea, Records of the Australian Museum 67 (2), pp. 25-53 : 47-48

Bama (Bama) aurantium n.sp.

Figs 39–41

Type material. Holotype ♂. Morobe Province: Stony Logging Area, near Bulolo [7°15'S 146°40'E], 25.iv.1979, H.R. ( AM K352856 ) . Paratypes. Morobe Province: 1 ♀ , same data as holotype ( AM); 1 ♂, 1 ♀ , Upper Manki Logging Area, near Bulolo , 5000 feet [c. 1500 m], 15.xii.1972 and 16.iii.1973, F.R.W., P.S. ( AM); 1 ♀ , Wau , Jan. 1974, R.K. ( NSMT); 1 ♂, 3 ♀♀ , Mount Missim, near Wau, Feb. , Mar. 1963, J.S. ( BPB). 1 ♀ , Milne Bay Province: Milne Bay, 1969, J.S., M.S. ( BPB) .

Description (♂, ♀). Moderately large, predominantly tawnyorange fly, with very lightly marked wing.

Coloration. Head predominantly dark reddish brown, darker towards vertex, with silvery pruinescence on postorbital to postgenal zone and on smaller parafacial to fronto-orbital zone. Antenna yellow to tawny-yellow; arista brown beyond base. Prelabrum dark brown; palpus tawnyyellow, becoming darker basally. Thorax tawny-orange. Coxae and femora tawny-yellow; tibiae and tarsi dark brown to blackish. Wing ( Fig. 39 ) largely hyaline, with faint yellow tinge anteriorly (intensified in subcostal cell), with brownish markings very restricted and pale compared with those of other species, except B. grande ; halter pale tawny, capitellum slightly darker. Abdominal tergite 1+2 tawny; other tergites becoming blackish posteriorly.

Head. Postfrons parallel-sided, near mid-length 0.36– 0.37× as wide as head; height of cheek 0.19–0.23 of height of eye; face in profile slightly concave above central depression, broadly convex below; fronto-orbital bristles of moderate size; postvertical bristle moderately small. Antennal segment 3 c. 2.5× as long as deep, rounded apically; segment 4 extremely short; segment 5 rounded, pubescent on distal margin, its length not distinctly greater than its diameter; segment 6 gradually tapered over c. basal third, with moderately developed pubescence, becoming sparser towards apex. Prelabrum moderately developed, slightly convex; palpus elongate, with few enlarged ventral bristles.

Thorax. Mesoscutum shining and sparsely pruinescent between setulae dorsally, more distinctly pubescentpruinescent laterally; scutellum finely pubescent on entire dorsal surface; mesopleuron largely glossy, with palepruinescent posterodorsal zone; prescutellar acrostichal bristle large, located slightly anteriorly to dorsocentral bristle; posteroventral margin of sternopleuron without black setulae. Fore femur with a series of large, stout posteroventral bristles and a longer series of smaller posterodorsal bristles; mid coxa with marginal comb of coarse black setulae, becoming very numerous and dense medially but not located on a defined lobe ( Fig. 40 ); hind basitarsus slender and subcylindrical in both sexes. Wing: first costal cell microtrichose towards margins, less distinctly so on large central area; second costal cell coarsely microtrichose, but with sub-basal almost bare zone; stem vein with dorsal tract of fine black setulae; vein 2 with slight flexure in front of anterior crossvein; second section of vein 4 with slight sigmoid curvature; penultimate section of vein 4 0.45–0.59 as long as anterior crossvein, 0.21–0.25× as long as discal crossvein; first and second basal and anal cells predominantly bare; anal crossvein most strongly bent on anterior part, but slightly variable.

Abdomen. Female: length of compound tergite 1+2 c. 0.6 of that of tergite 3; sternites 2 and 3 rather large; sternites 1 and 4 shorter; sternites 5 and 6 very short, but sclerotised. Male: sternite 4 without cleft; aedeagus ( Fig. 41 ) with preglans expanded into broad partly membranous rounded lobe bearing many fine peg-like spinules; flexible section elongate, c. as long as glans when straightened out; glans ovoid with short distal lobe, ensheathing hatchet-like sclerite; bulb less than half as long as glans, curved basally, swollen distally; left terminal filament c. 0.6 as long as glans, right terminal filament much shorter.

Dimensions. Total length, ♂ 8.1–8.4 mm, ♀ 7.3–8.2 mm; length of thorax, ♂ 3.6–3.7 mm, ♀ 3.6–3.7 mm; length of wing, ♂ 8.8–9.0 mm, ♀ 8.5–8.9 mm; length of glans of aedeagus, 0.40 mm.

Notes. Bama aurantium has the palest general coloration of any Bama sp., except B. grande . The wing venation most resembles that of B. papuanum , but details of the aedeagus differ from that species and approach those of B. monstrans . In the absence of strong black setulae on the posteroventral margin of the sternopleuron, B. aurantium resembles B. monstrans and B. papuanum , but differs from most other species. The armature of the mid coxa, including the dense brush of coarse black setulae ( Fig. 40 ) is unique in the genus.

The specific epithet is a noun in botanical Latin—an orange, in reference to the coloration of the thorax.

Figures

Figures 39–41. Bama aurantium n.sp. (39) Wing of female (Stony Logging Area).(40) Mid coxae, male.(41) Distal part of aedeagus (Upper Manki), scale = 0.2 mm.bu, bulb; fs, flexible section of aedeagus; g, glans; lg,