Microepicausta fenestra, Mcalpine, 2019

Mcalpine, David K., 2019, Review of the Australian Signal Flies of the Genus Microepicausta (Diptera: Platystomatidae), Records of the Australian Museum 71 (3), pp. 95-104 : 98-100

Microepicausta fenestra sp. nov.

http://zoobank.org/NomenclaturalActs/ 2AB7C9FE-2818-4717-94BD-29DF293A384F

Figs 4–7

Holotype ♂. Queensland: 13 km W of Musgrave [14°48'S 143°23'E, 220 m], 14.i.1994, G.D., A.D., R.E., mercury vapour lamp ( AM K.504392). Double-mounted on micro-pin through polyporus . Paratypes. Queensland: same data as holotype 1♂, 2♀♀ ( AM) .

Other material. Northern Territory: Rimbija I., Wessel Islands , [11°01'S 136°45'E], Feb. 1977, T.A.W., R.A.B., 1♂ ( AM), 3♂♂, 1♀ ( ANIC) .

Description (♂, ♀). Somewhat elongate black, largely shining fly.

Coloration. Head with largely black to brown-black ground-colour, with major bristles black, most minor setulae or hairs whitish; postfrons with silvery-grey pruinescent orbital margins; parafacial broadly silvery-grey pruinescent on tawny-brown cuticle, pruinescent zone extending over cheek region and on to lower postocular zone, but not on to extensively shining black occipital region; face shining black, its approximate upper half with zone of fine silvery-grey pruinescence narrowly or indistinctly divided on median line, occiput with small whitish-pruinescent zone above cervical foramen. Antenna tawny-brown; segment 3 becoming darker distally; arista brown to blackish. Prelabrum shining black; palpus brown, often with narrowly yellowish apex. Thorax largely shining to subshining black with blue to green reflections, with major bristles black and most fine hairs or setulae white; mesoscutum with median whitish-pruinescent stripe on whole length and lateral pruinescent zone on notopleural region; mesopleuron with extensive posterodorsal whitish-pruinescent zone; propleuron and substantial zone below mid coxa on sternopleuron whitish-pruinescent; posterior parts of pleura with pruinescence of varying density; scutellum black, almost without pruinescence. Coxae brown with grey pruinescence, palest on fore coxa; femora and tibiae brown-black; fore tarsus dark brown; other tarsi dull yellow with brown apices. Wing with nebulous brown anterodistal zone covering region from distinctly beyond end of vein 1 to apex of vein 4; anterior crossvein and discal crossvein each surrounded by compact brown suffusion; veins brown. Halter pale brown basally, with pale yellow capitellum. Abdominal tergites and sternites shining black.

Head in profile higher than long, with postfrons much longer than face; face rather short and broad, with only slightly raised median elevation, thus concave in profile; height of cheek c. 0.15–0.22 of height of eye. Antennal segment 3 tapered to subacute apex; arista almost bare, except for trace of minute pubescence near base. Prelabrum moderately large and deep, slightly receding below; palpus moderately large, setulose, broadly rounded apically.

Thorax elongate; humeral callus and mesoscutum very extensively haired; in female only, humeral callus with tuft of slightly longer black setulae behind humeral bristle, these undifferentiated in male; scutellum shorter than semicircle in dorsal view, with hairs rather long and generally distributed, but not dense; mesopleuron with numerous long hairs, mainly on posterior part; sternopleuron extensively haired. Fore femur with a series of long, fine posteroventral bristles, without differentiated dorsal bristles; other femora without distinct bristles; mid tibia with single large terminal ventral spur and several much smaller ones; legs otherwise without well developed armature. Wing as in Fig. 5 ; first costal cell, much of second costal cell, basal part of first basal cell, almost entire second basal and anal cells bare; alula bare; most of rest of wing membrane almost uniformly microtrichose.

Abdomen. Preabdomen and female postabdomen with the general characters of the genus. Male postabdomen: anterior and posterior surstyli and cercus of similar length and prominence; outer (anterior) surstylus with single long terminal setula, its concave posterolateral surface with fine, dense, plush-like pubescence; inner surstylus without apparent surface armature, with attenuated basal articulation; cercus with numerous long setulae, on posterior surface with long, dense, erect pubescence; membranous aedeagal sheath (containing aedeagal apodeme) elongate, but not prominently projecting (at least in type material); stipe of aedeagus distally with transparent membranous wing, which does not extend on to the otherwise slightly differentiated preglans; terminal bulb of glans compact and sclerotized, bearing an elongate, tapering process; terminal filament c. 2.4× as long as glans, simple, not much tapering distally.

Female postabdomen: aculeus broader than in M. gracilis and M. wirthi , not tapering distally, rounded at apex.

Dimensions. Total length, ♂ 5.0– 6.5 mm, ♀ 5.0– 5.6 mm; length of thorax, ♂ 2.1–2.2 mm, ♀ 2.0– 2.1 mm; length of wing, ♂ 4.4–4.5 mm, ♀ 4.1–4.2 mm; length of glans of aedeagus 0.3 mm.

Distribution. Queensland: Cape York Peninsula. Northern Territory: Wessel Islands.

Notes. This species is readily distinguished from the other known Australian species of Microepicausta by the characters given in the key to species. The dark brown palpus, the whitish pruinescence on the upper part of the otherwise black prelabrum, and the largely bare anal cell help to differentiate M. fenestra from some non-Australian species, several of which are undescribed.

The specific epithet is a Latin noun meaning window, in reference to the clear zones lacking microtrichia in the anal cell and first and second basal cells of the wing.

Figures

Figures 4, 5. Microepicausta fenestra sp. nov., holotype male. (4) head and part of thorax. (5) right wing.

Figures 6, 7. Microepicausta fenestra sp. nov., Musgrave, Qld. Details of male postabdomen. (6) Right cercus and surstyli. Scale = 0.1 mm. (7) Aedeagus and associated structures. Scale = 0.3 mm. aa, aedeagal apodeme; as, aedeagal sheath; b, bulb of aedeagus; g, glans; mw, membranous wing of stipe; pa, process of aedeagal apodeme (paired); pg, preglans; st, stipe; tf, terminal filament; tp, terminal process of bulb.