Bama (Bama) gressitti, 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 : 39-41

Bama (Bama) gressitti n.sp.

Figs 23–26

Type material. Holotype ♂. Eastern Highlands Province: Karimui, S. of Goroka , 1000 m, 6.vi.1961, J.L.G., M.G. ( BPB). Impaled on large black pin, thorax damaged, mid legs broken off beyond trochanters, right wing damaged, left wing on slide . Paratype. Eastern Highlands Province: 1 ♀, same data as holotype, except 5.vi.1961 ( BPB). Legs and wings intact, left wing on slide .

Description (♂, ♀). Moderately small, largely blackish fly, with sexually dimorphic wing pattern.

Coloration. Head dark brown to blackish, with narrow silvery-pruinescent stripe along eye margin on anterior part of postfrons and upper part of parafacial, broadened where the two regions meet; upper part of face with silvery-pruinescent zone; postorbital pruinescent zone extending on to cheek. Antenna tawny-brown, including arista. Prelabrum shining dark brown; palpus dark grey-brown. Thorax brown-black, predominantly shining. Legs: fore coxa dark brown; mid and hind coxae tawny-brown; femora dull yellow basally, brown distally; tibiae and tarsi brown, latter often darker. Wing of male ( Fig 23 ): area of membrane anterior to vein 4 largely rather dark brown, paler in both costal cells, and with single long hyaline zone in first posterior cell, which does not reach base, anterior crossvein, and vein 3; distal part of wing anterior to vein 4 with some diffuse paler zones, and a series of dark brown connected spots on each side of vein 3 and vein 4 (details in Fig. 23 ); light brown suffusion enclosing discal crossvein and, less strongly, distal part of vein 5; small brown suffusion covering short second section of vein 5; posterior parts of wing otherwise largely hyaline. Wing of female ( Fig. 24 ): differing from above mainly in the more uniformly dark brown anterodistal region, with no trace of spotted pattern, with hyaline zone in first posterior cell reduced and divided in two, and with brown suffusion surrounding vein 4 more marked than in male. Halter dull yellow. Abdomen shining black.

(25) Right hind tarsus of male. (26) Abdomen of male, sternites 3 and 4 (on left).

Head. Postfrons near mid-length 0.37× as wide as head; height of cheek 0.24 of height of eye; face with depression across mid-length, convex below; posterior fronto-orbital bristle moderately small, anterior one much smaller; ocellar and postvertical bristles very fine. Antennal segment 3 c. 2.7× as long as deep, apically rounded; segment 4 very short; segment 5 longer than wide, apparently bare; segment 6 slender beyond base, coarsely pubescent on most of length, more finely so towards apex. Prelabrum rather deep, slightly more so in male; palpus of moderate size.

Thorax. Mesoscutum almost bare between sockets of setulae except towards slightly pruinescent lateral margins; scutellum minutely pubescent dorsally; pleura largely shining, with very little pruinescence, but becoming densely pruinescent posteriorly; prescutellar acrostichal bristle well developed, rather widely spaced. Fore femur with slender posteroventral bristles, developed mainly on distal half, and with mainly shorter posterodorsal bristles; mid tibia with one long and one very short apical spur; mid basitarsus elongate, cylindrical, c. 0.59× as long as mid tibia (female); hind tarsus of male ( Fig. 25 ) almost as long as hind tibia; hind basitarsus of male broadened, its length 0.49 of that of hind tibia, that of female only slightly less broadened. Wing: first costal cell almost entirely bare; second costal cell with broad bare basal zone; discal cell almost entirely microtrichose; first basal cell with bare zone covering much of hyaline area; second basal and anal cells with quite small distal microtrichose zones; vein 2 with gentle sigmoid curvature; distal sections of veins 3 and 4 very slightly convergent towards apex; penultimate section of vein 4 c. 0.7 of length of discal crossvein; discal crossvein straight, almost transverse; anal crossvein bent very near anterior extremity.

Abdomen. Male ( Fig. 26 ): sternite 4 longer than sternite 3, divided by median membranous channel except at anterior extremity; outer surstylus much narrowed near end of inner surstylus, with broad apical expansion, acutely angular on its basal side; other details of genitalia not observed. Female: tergite 1+2 much shorter than tergite 3; sternite 2 longer and narrower than other sternites; sternite 4 short, undivided.

Dimensions. Total length, ♂ 6.7 mm, ♀ 5.5 mm; length of thorax, ♂ 2.6 mm, ♀ 2.7 mm; length of wing, ♂ 7.1 mm, ♀ 6.7 mm.

Notes. Bama gressitti resembles other dark-coloured Bama species with the wing area in front of vein 3 extensively darkened (e.g., B. flexifer ), though the male only has the distal part curiously variegated ( Fig. 23 ). The slight brown suffusion around the distal part of vein 5, the straight discal crossvein and the dark palpus aid specific identification, while such deeply divided male sternite 4 is so far otherwise known only in B. bickeli .

The specific epithet refers to the collector J. Linsley Gressitt, formerly of the B.P. Bishop Museum.

Figures

Figures 23–26. Bama gressitti n.sp. (23) Left wing of male. (24) Left wing of female.