Microepicausta wirthi, 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 : 100-104

Microepicausta wirthi sp. nov.

http: //zoobank.org/NomenclaturalActs/ CF393AE4-A085-4984-855E-119CE53976BC

Figs 8–12

Holotype ♂. New South Wales: Nullica Beach, near Eden [37°06'S 149°53'E], 17.xi.1997, R.M., D.K.M., on Spinifex [presumably S. sericeus ] ( AM K.504393). Glued to card mount. Paratypes. New South Wales: same data as holotype, 20♂♂, 14♀♀ ( AM), 4♂♂, 5♀♀ ( USNM); Nadgee [37°28'S 149°58'E], Jan. 1967, J.W. 2♂♂, 1♀ ( AM); Merimbula, Jan. 1960 –1966, K.R.N., 2♂♂, 2♀♀ ( ANIC); Narooma, Jan. 1963, Z.L. 1♂, 1♀, ( AM), 2♂♂ ( ANIC).

Other material examined (localities only given). New South Wales: Red Rock, near Woolgoolga ( AM); North Beach, Bellinger River ( AM); Nambucca Heads ( ANIC); Camden Head, near Harrington ( AM); Toukley ( ANIC); Terrigal ( ANIC); Turimetta Beach, near Sydney ( AM); Dee Why, near Sydney ( Fig. 13 , AM, USNM); Durras, near Bateman’s Bay ( ANIC); Broulee ( ANIC). Queensland: Queen’s Bay, Bowen ( ANIC); Yeppoon ( ANIC); Broadbeach, Gold Coast ( ANIC). Tasmania: Stumpy’s Beach, Mount William National Park ( AM); Ironhouse Point, near Falmouth ( AM). SouthAustralia: vicinity of beach, Victor Harbour ( AM).

Description (♂, ♀). Elongate rather small fly, of pale colour for genus, due to extensive whitish pruinescence on much of otherwise largely dark thoracic cuticle.

Coloration (geographically variable). Head largely yellow with white bristles and setulae; fronto-orbital plates broadly white-pruinescent; frontal triangle forming brown-black spot surrounding ocelli, often larger and more distinct in males; upper occipital region with extensive dark brown cuticular zone, covered with dense greyish white pruinescence; facial carina often partly brownish. Antennal segment 1 yellow; segment 2 yellowish brown (female) to dark brown (typical males); segment 3 greyblack (typical males) or partly yellowish (typical females); arista brown. Palpus yellow; prelabrum brownish, usually paler in females. Thorax typically with shining black ground colour and extensive covering of dense grey-white pruinescence, often more extensive in female, dorsally usually with paired black markings, more developed in males than females; sternopleuron typically with broad shining blackish central zone, and pale pruinescent zones on dorsal and ventromedian margins; scutellum with variable extent of pale dorsal pruinescence, often more developed in female. Wing transparent, without darker markings or shading; veins largely yellowish; distal parts of costa and veins 3 and 4 brown; setulae on vein 1 all pale; halter yellow. Legs yellowish, extensively variegated with brown, more so in males, particularly those of southern populations.Abdominal tergites and sternites shining black or brown-black, with whitish setulae; pleural membrane largely yellowish.

Head in profile c. as long as high, with postfrons forming acute angle with face; eye small for genus, less than twice as high as cheek; facial carina narrow but elevated, with rounded summit. Antennae in male large, extending at least to lower margin of face; arista bare. Prelabrum much reduced, not prominent in profile; palpus moderately short.

Thorax elongate; mesoscutum extensively haired, humeral callus less so; scutellum almost semicircular in dorsal outline, with long but not dense dorsal hairs; mesopleuron, pteropleuron, and much of sternopleuron with numerous hairs. Femora armed as in M. fenestra ; mid tibia with one large terminal ventral spur. Wing as in Fig. 12 ; membrane entirely microtrichose.

Male postabdomen. Outer surstylus moderately broad, sheathing, simple in shape, its apex very slightly exceeding that of inner surstylus, with sparse minute setulae; inner surstylus with one sharply acuminate apical prensiseta and one short compact prensiseta on anterior surface far from apex; aedeagus with simple glans, lacking sclerotized bulb and associated process; terminal filament moderately long and tapering.

before urbanization of the area, shows a typical habitat for Microepicausta species: sandy and close to the seashore

Female postabdomen distally very slender; aculeus very small, attenuated, not dorsoventrally compressed, not tapered distally.

Dimensions. Total length, ♂ 3.5–6.0 mm, ♀ 3.9–5.4 mm; length of thorax, ♂ 1.1–1.9 mm, ♀ 1.4–2.0 mm; length of wing, ♂ 2.9–4.1 mm, ♀ 3.5–4.6 mm; length of glans of aedeagus 0.20 mm.

Distribution. East coast of Queensland and New South Wales from Bowen district southwards; Tasmania—east coast as far south as Falmouth district; South Australianear Victor Harbour. The species is evidently restricted to sandy habitats near the sea-shore (see, for example, Dee Why before urbanization, coastal New South Wales near Sydney, early twentieth century, Fig. 13 ). Although we have no material from Victoria, I consider it probable that the species lives in that state.

Notes. Microepicausta wirthi is distinguished from other species of the genus by the extensive dense whitish pruinescence covering most of the black thoracic cuticle, and the entirely pale cephalic and thoracic bristles. The anteriorly pointed head-profile, the small eyes, and reduced prelabrum are also distinctive.

The specific epithet refers to Willis W. Wirth, formerly of the National Museum of Natural History, Washington D.C., who drew my attention to this species when visiting Australia in 1957.

ACKNOWLEDGMENTS. John C. Martin produced the photographic illustrations. Helen M. Smith gave much help in organizing the manuscript. Daniel F. Bickel, Russel Cox and Shane F. McEvey gave general support. Names of collectors are given in the Introduction.

Figures

Figure 13. This depiction of Dee Why, New South Wales (near Sydney), painted by Jules Pierre (Jan) De Leener (1873–1944)

Figures 8, 9. Microepicausta wirthi sp. nov., Nullica Beach, NSW. (8) Holotype male. (9) Female, head and thorax.

Figures 10–12. Microepicausta wirthi sp. nov., Nullica Beach, NSW. Details of male postabdomen. (10) Right surstyli and fused cerci. Scale = 0.1 mm. (11) Aedeagus (retouched) and associated structures. Scale = 0.2 mm. (12) Left wing.