Scathophaga stercoraria
The 'common yellow dung fly'. One of the most abundant and ubiquitous of British flies. 'Typical' males are yellow and furry, whilst females are greenish and bristly. However, smaller males frequently lack the yellow furry appearance and are more like a female in general appearance. These were sometimes given specific status (S. merdaria) in the past, although most recent works refer to these (if at all) as no more than a colour form. Small individuals may be sterile (Gibbons, 1980[1]). Large and rather more orange coloured males seem to occur in northern Scotland which could easily be mistaken for S. scybalaria. Wing length: ♂ 4.9 - 7.4 - 9.5 mm (54); ♀ 4.1 - 6.2 - 8.0 mm (62).
References
Larvae develop most frequently in cow dung, although they have been bred from the dung of a wide variety of other species including dog, human, sheep and horse according to Skidmore in Stubbs & Chandler (1978)[1]. Eggs are typically laid in fresh cow dung and the larvae are predatory on other insect larvae within the dung. Adult males are usually seen on or near fresh cow pats where they wait for females to arrive and attempt to intercept them to mate. There is intense competition between males and fights are frequent and it is not unusual to see a female at the centre of a struggling ball composed of a number of males. Females particularly disperse from breeding areas into hedgerows and woods where they are voracious predators on other flies and there is quite extensive literature on their prey selection. Both sexes are often found visiting flowers, such as umbels of hogweed (Heracleum sphondili) where they both feed from the flower and hunt other insects which the flower attracts.
Both the adult mating strategies and larval competition within the cow pat are frequent subjects for study and there is a huge literature on this species. It has a very long season and adults can be found at any time of year including mid-Winter (Blackith & Blackith, 1990[2]).
References
This is an easy species to recognise and shouldn't easily be confused with other Scathophaga species. The combination of plumose arista, hairy pteropleuron and dark antennae are definitive. Large, more than usually orange furred males are sometimes mistaken for S. scybalaria, but that species has orange antennae.
One of the commonest and most familiar flies throughout the British Islaes. Although it is most abundant in farmland where cattle are to be found, specimens can be found in any habitat from city centres (where it can breed in dog dung - Disney, 1973[1]) to the tops of mountains (I have found specimens, with S. furcata, on reindeer dung near the top of Cairngorm).
World distribution: Palaearctic: Andorra, Austria, Azores, Balearic Islands, Belgium, Bulgaria, Canary Islands, Czech Republic, Denmark, Estonia, Faeroe Islands, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Lithuania, Madeira Islands, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Spain, Sweden, Switzerland, Turkey, Yugoslavia; Russia: European and eastern Palaearctic; North Africa; Asia: Kashmir; Nearctic: Canada, USA; Neotropical: Brazil; Afrotropical: South Africa.