Ernoneura argus
A small, brown, bristly fly with wing markings that make it very distinctive. The fore margin is brownish and the wing membrane has numerous round brown spots placed adjacent to the main veins and mostly with a veinlet, or at least a trace of one at the centre. Occiput, thorax and abdomen brownish yellow. Frons and basal antennal joints red-brown. Face and jowls dusted pale grey. Palps yellowish and elongate. Proboscis shining black. Thoracic dorsum with shining black stripes. Wing length: ♂ 4.4 - 5.1 - 5.9 mm (2); ♀ 5.0 - 5.3 - 5.7 mm (4).
The larvae is aquatic and its biology is described by Nelson (1989)[1]: Adults brought into captivity readily mated and females laid eggs when provided with moss containing caddis egg masses. Newly hatched larvae congregated on the egg masses where they appeared to feed on the surface of the jelly, rather than on the eggs themselves. Larvae were not successfully reared in captivity, but mature larvae were found in the field amongst water washed roots of a Scot's pine projecting into the edges of Loch Mallachie. This substrate supported little other life apart from tipulid larvae and oligochaete worms. Available adults records are all date from June and July.
References
Found beside oligotrophic lochs with shingle or boggy edges. Adults 'skate' low over the water surface. This is a species of tundra lake shores and is recorded from very few localities in Britain. It was first discovered at Loch Garten (Sharp, 1910)[1] and this remains its best known locality (including Loch Mallachie - on the same reserve) and one where it can be found in abundance (records from 1906, 1910, 1935, 1967, 1982, 1988, 1991, 2008). Sharp also reports that Yerbury had previously found it near Thurso and Collin (1958)[2] adds Loch Einich, Speyside (Collin's specimen dated 1933). There are specimens in the collection of the Natural History Museum from Loch Etchachan, Aberdeenshire (taken by Coe in 1951) and a small lochan on Lewis (caught by Bloomfield & Vardy in 1962) and a published record from a lochan near Loch Ericht, Perthshire (Horsfield, 1989)[3]. A record from a small lough on Harbottle Moors, Northumberland in 1980 was submitted to the ISR by Ian Wallace. Adults in May to August. This appears to be a widespread, but decidedly northern, Holarctic species which Vockeroth (1987)[4] describes as "Arctic" in North America and Gorodkov (1984)[5] lists from Siberia, Taimyr and north of Western Europe.
World distribution: Palaearctic: Finland, Lithuania, Norway, Poland, Sweden; Russia: European regions and eastern Palaearctic; Nearctic: Canada, USA (Alaska).
References
- , 1910. Two Diptera new to Britain. Entomologist's monthly Magazine, 46, pp.274-275.
- , 1958. A short synopsis of the British Scatophagidae (Diptera). Transactions of the Society for British Entomology, 13, pp.37-56.
- , 1989. A record of Ernoneura argus (Zett.) (Dipt., Scathophagidae) from Perthshire. Entomologist's monthly Magazine, 125, p.230.
- , 1987. Scathophagidae. Agriculture Canada Monographs, 28, pp.1085-1097.
- , 1984. Family Scthophagidae. In Keys to the Insects of the European Part of the USSR. Keys to the Insects of the European Part of the USSR. 1984. pp. 732-759.