Microepicausta gracilis Hendel, 1914

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 : 97

Microepicausta gracilis Hendel

Figs 1–3

Microepicausta gracilis Hendel, 1914a: 54 , pl. 5, figs 101, 102 (no specific description); 1914b: 85–86 (description).

Elassogaster terrae-reginae Malloch, 1928: 352–353 ; Malloch, 1931: 22, syn. nov.

Type material. I made the following notes on type material of M. gracilis in MNM, Budapest, in April 1973: holotype ♀, i.e. specimen of which both head and wing were figured [ Hendel, 1914a, pl. 5, figs 101, 102], Australia, L. Biró 1900, Sydney Botany B. Second specimen ♀, same data, is not a type, though labelled as such. Third specimen of series, also labelled “type” is a small ♀ of Rhytidortalis rugifrons . I have labelled it so, but the species is now provisionally given as Duomyia rugifrons (Thomson) according to McAlpine (2000).

Types of E. terrae-reginae : holotype ♂, Queensland: Townsville , 1.iv.1922 (in cop), G. F.H. ( AM K.90460, formerly in SPHTM); allotype ♀, same data, “fragmentary”, only wings remaining ( AM K.90461) .

Other material (localities only given). New South Wales: Iluka ( AM); Angourie ( AM); Red Rock, near Woolgoolga ( AM); Tucker’s Rock, near Repton ( AM); Bundagen, near Repton ( AM); Harrington ( AM); Manning Point, near Taree ( AM); Black Head, near Halliday’s Point ( AM); Shoal Bay, near Port Stephens ( AM); Toukley ( ANIC); Woy Woy ( ANIC); Narrabeen ( AM); Dee Why, near Sydney ( Fig. 13 , AM); Bronte, near Sydney ( AM); Cook’s River, near Sydney ( AM); Kurnell ( AM); North Cronulla ( AM); Grey’s Point, near Cronulla ( AM); Durras ( ANIC); Ulladulla ( ANIC); Bendalong ( AM); Broulee ( ANIC); Narooma ( AM, ANIC); Wallagoot Lake ( ANIC); Merimbula ( AM); Nadgee, near Eden ( AM). Queensland: Cliff Island, Princess Charlotte Bay ( ANIC); Palm Islands, near Ingham ( QM); Deepwater National Park, S of Agnes Water ( AM); Mooloolaba, near Maroochydore ( ANIC); Caloundra ( QM); Bribie Island ( QM); Nerang river, near Surfers Paradise ( ANIC).

Description (♂, ♀). Resembling M. fenestra in most characters, except as indicated below.

Coloration mostly as for M. fenestra . Postfrons often partly tawny-brown. Palpus dark brown to black. Mesoscutum with median whitish pruinescent stripe, but no pale pruinescent lateral zone; mesopleuron with separate anterior and posterior whitish-pruinescent zones, latter zone extending on to sternopleuron. Fore coxa yellow; other coxae largely brownish; femora usually brown, often becoming yellowish towards bases; fore tarsus black; other tarsi brown to yellowish. Wing markings and halter approximately as in M. fenestra . Abdomen black.

Head with postfrons generally slightly longer than face. Antenna approximately as in M. fenestra ; segment 3 tapered apically.

Thorax. Humeral callus with only moderately developed hairs. Legs with armature resembling that of M. fenestra . Wing venation very like that of M. fenestra but showing considerable variation in details of proportion and contour; much or all of second costal cell, first and second basal cells, anal cell and alula almost uniformly microtrichose.

Male postabdomen: stipe very long, with small, compact glans, without secondary elongate process, but bearing single very long, distally tapered, simple terminal filament with terminal gonopore.

Female postabdomen: aculeus tapering to finely acuminate apex.

Dimensions. Total length, ♂ 3.1–5.7 mm, ♀ 4.1–5.7 mm; length of thorax, ♂ 1.1–2.3 mm, ♀ 1.4–2.1 mm; length of wing, ♂ 2.7–4.9 mm, ♀ 3.5–4.7 mm.

Distribution. Queensland: coastal districts from Princess Charlotte Bay southwards. New South Wales: coastal districts generally.

Notes. It was initially difficult to evaluate variation in the collections belonging to this species or apparent complex, because of variation in pigmentation of the legs (particularly of the femora) and the apparent form of the elongate hypandrial tube. Study of numerous specimens of both sexes shows that the variation in leg coloration is unlikely to have taxonomic significance. Careful preparation of the male postabdomen seems to indicate that the apparent differences are not due to structure, but to the position in which the hypandrial tube became lodged when the insect died.

Figures

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

Figures 1, 2. Microepicausta gracilis Hendel, male, Bronte, NSW. (1) Head and part of thorax. (2) Right wing.

Figure 3. Microepicausta gracilis Hendel, Bronte, NSW. Details of male postabdomen, from retouched photograph. Scale = 0.5 mm. c, cercus; e, epandrium; g, glans; is, inner surstylus; st, stipe; tf, terminal filament.