Bama (Bama) divergens, 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 : 30-31

Bama (Bama) divergens n.sp.

Figs 3, 4

Type material. Holotype ♂ (unique). Morobe Province: Upper Watut [River, i.e. probably district to W of Bulolo and Wau, other label data indecipherable], J.S., M.S. ( BPB). Impaled on large pin, left wing damaged.

Description (♂, ♀ unknown). Moderately small, largely black fly, with distinctive wing markings (perhaps sexually dimorphic).

Coloration. Head dark brown to blackish; parafacial with silvery-pruinescent line which broadens at level of antennal socket; face grey-pruinescent except towards lower margin, more densely so in upper part of antennal fovea; postorbital silvery-pruinescent zone very broad, extending broadly on to cheek region. Antenna tawny-orange; arista brownish. Prelabrum dark brown; palpus tawny-yellow. Thorax black, largely shining. Coxae brown; fore coxa largely finely grey-pruinescent and with whitish setulae; fore femur tawny-brown on c. basal half, becoming yellow distally, but brownish again at apex; other femora yellow; tibiae tawnybrown; tarsi brown. Wing: brown zones anterior to vein 5 as in Fig. 3 , no brown zones posterior to vein 5 except for small spot on anterior part of anal crossvein; pair of intensely black spots in distal part of first posterior cell. Halter yellow, with black capitellum. Abdomen shining black.

Head. Postfrons at mid-length 0.32× as wide as head; height of cheek c. 0.15× that of eye; face almost flat, but becoming slightly prominent towards lower margin; posterior fronto-orbital bristle large, anterior one damaged, but probably large; ocellar bristle very minute; postvertical bristle moderately small. Antennal segment 3 c. 3.5× as long as deep; segment 4 very short; segment 5 cylindrical, rather short; segment 6 slender beyond base, coarsely pubescent on whole length. Prelabrum shallow; palpus much deeper, moderately long.

Thorax with only very slight development of pruinescence, but scutellum minutely pubescent as in related species; prescutellar acrostichal bristle large. Fore femur with short posteroventral bristles distally, with long, slender, spaced posterodorsal bristles; mid tibia with one moderately large and one very small apical spur; mid basitarsus very slender, cylindrical; hind tarsus ( Fig. 4 ) c. 0.93 of length of tibia; hind basitarsus moderately slender, subcylindrical, its length c. 0.49 of that of tibia. Wing: first costal cell bare, except in anterodistal angle; second costal cell, first basal cell, and discal cell entirely microtrichose; second basal cell microtrichose on at least distal third; vein 2 with very slight almost uniform curvature; distal sections of veins 3 and 4 almost straight, broadly divergent; penultimate section of vein 4 only slightly shorter than discal crossvein; discal crossvein curved; anal crossvein abruptly curved at c. anterior third of length.

Abdomen. Sternite 3 rather large and squarish; sternite 4 slightly shorter, quadrate, neither divided nor incised; sternite 5 similar, but shorter again. Cercus rather short and simple; apical section of outer surstylus apparently small and rounded; other postabdominal parts not observed.

Dimensions. Total length, 6.2 mm; length of thorax, 2.6 mm; length of wing, 6.6 mm.

Notes. The general distribution of pruinescence on the face and the rather large fronto-orbital bristles of Bama divergens are characters otherwise found in B. bipunctatum , as is the black capitellum of the halter (at least in males). Bama divergens differs from B. bipunctatum in the pattern of wing markings ( Fig. 3 ) and the different contour of the anal crossvein. It differs from all other known Bama species in the almost straight and widely divergent distal sections of veins 3 and 4. The two black spots near the costal margin of the first posterior cell are reminiscent of those observed in males (? only) of B. bipunctatum , and may therefore be absent in females. Unlike B. bipunctatum , B. divergens has these spots on an almost hyaline, instead of dark brown zone.

The specific epithet is a Latin participle, referring to the distal divergence of veins 3 and 4.

Figures

Figures 3, 4. Bama divergens n.sp., male. (3) Left wing. (4) Right hind tibia and tarsus.