Bama (Bama) signifer, 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 : 36

Bama (Bama) signifer n.sp.

Figs 17–20

Type material. Holotype ♀ (unique). Milne Bay Province (highlands of NE): Agaun , 4400 feet [c. 1340 m, c. 9°55'S 149°21'E], Aug. 1969, R.P. ( ANIC). On micropin through polyporus.

Description (♀, ♂ unknown). Slightly elongate brown to blackish fly, with wing heavily marked anteriorly to vein 4.

Coloration. Head largely brown, shading to black on vertex and much of occiput, with silvery pruinescence on postorbital to postgenal zone. Antenna tawny-brown; arista becoming darker distally. Prelabrum tawny-brown; palpus grey-brown. Thorax largely dark brown; mesoscutum predominantly shining black. Legs: coxae tawny; mid coxa with larger setulae black, finer ones yellow; femora yellow; tibiae tawny-brown; tarsi darker-brown. Wing ( Fig. 17 ) anteriorly to vein 4 largely brown-black, with first costal and base of second costal cell yellow, extreme base of marginal cell mid-brown, and hyaline zones in first basal and first posterior cells; behind vein 4 membrane largely hyaline, with narrow brown zone in second posterior cell along vein 4 and three small brown zones in discal cell; halter entirely pale yellow. Abdomen dorsally tawny to brownish; tergite 1 and lateral parts of tergite 2 blackish.

Head. Postfrons almost parallel-sided, near mid-length c. 0.39× as wide as head; height of cheek c. 0.23 of height of eye; face in profile mainly concave, becoming flat towards lower margin; fronto-orbital bristles apparently rather small (damaged); postvertical bristles very fine, closely placed. Antennal segment 3 c. 2.5× as long as deep, apically rounded; segment 4 prominent, rounded; segment 5 bare, relatively elongate, length distinctly more than twice its maximum diameter; segment 6 ( Fig. 19 ) quite bare, becoming attenuated shortly beyond base, with leaf-like subapical expansion (palette). Prelabrum rather shallow, not prominent; palpus short, moderately broad but not distally expanded.

Thorax. Mesoscutum almost bare between setulae on much of dorsal surface, pubescent-pruinescent laterally; scutellum pubescent on entire dorsal surface; mesopleuron partly glossy, with very little pruinescence centrally and posteriorly; prescutellar acrostichal bristle absent; single pair of dorsocentral bristles more closely placed than in other species. Fore femur with stout posteroventral bristles on distal half and smaller posterodorsal bristles; mid coxa with distomedial lobe not narrowly produced, with large and small setulae. Wing ( Fig. 17 ): much of first costal cell and small basal zone of second costal cell bare; stem vein with few minute dorsal setulae; vein 2 curved but not abruptly flexed; second section of vein 4 moderately curved; penultimate section of vein 4 c. as long as anterior crossvein, almost 0.7× as long as discal crossvein; second basal and anal cells and basal hyaline zone in first basal cell largely bare; anal crossvein strongly curved on anterior part, with slight concave curvature posteriorly.

Abdomen ( Fig. 20 ). Compound tergite 1+2 subequal in length to tergite 3; sclerotized part of segment 7 (oviscape) almost as long; sternites 1, 2, and 3 large; sternite 4 relatively small; sternites 5 and 6 apparently very short (not clearly visible in type).

Dimensions. Total length, 6.0 mm; length of thorax, 2.4 mm; length of wing, 7.0 mm.

Notes. The complete absence of prescutellar acrostichal bristles and the bare arista ( Fig. 19 ) distinguish B. signifer from all other known species of Bama . The presence of a subapical palette on the arista is an unusual condition of the female holotype. In males of a number of platystomatid species in several other genera an aristal palette is present, but in these the palette is generally absent in females. In Euprosopia maculipennis (Gúerin-Méneville) the palette is present in both sexes, but smaller in the female. I expect that the presently unknown male of B. signifer will be found to have the palette at least as developed as in the female.

The specific epithet is a Latin noun, meaning flag-bearer, in reference to the palette of the arista.

One specimen (unsexed, abdomen missing) from Mount Missim, Morobe Province (labelled Bama sp. P, BPB) has the contour of vein 2 and wing markings much as in B. signifer , except that the discal crossvein is enclosed in a brown mark. However, the arista is creamy-white and pubescent on its whole length, without apical expansion. I regard its specific status as indeterminate at present.

Figures

Figures 17–20. Bama signifer n.sp., holotype female. (17) Left wing. (18) Right mid coxa, anteroventral view. (19) Distal half of left arista, scale = 0.2 mm. (20) Dorsal view of abdomen, sclerites outlined only.