Scathophaga stercoraria (L.)   
Common Yellow Dung Fly

Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Hexapoda
Class: Insecta
Order: Diptera – true flies

British distribution: Common throughout Britain.
World distribution: Northern hemisphere, widespread.

Scathophaga stercoraria, male
Scathophaga stercoraria male, close-up.
Note the 'haltere', the drumstick-like balancing appendage that replaces the rear wing on each side of the body.

Scathophaga stercoraria, group on dung
Scathophaga stercoraria, gathering of males on pony dung, Wicken Fen, Cambridgeshire, September 2004.

The bright golden-yellow males of Scathophaga stercoraria (family Scathophagidae) are a familiar sight on cow-pats and on other dung in pastures. They are predators, taking smaller flies and other insects that visit the dung, but they also wait for the arrival of females that visit the dung more briefly to mate. Both males and females may mate multiple times and there is a substantial body of literature on the competition between males and on the factors that determine mating success. The females return to the dung to lay their eggs, the larvae being dung detritivores.

As a true fly it has just a single pair of wings, the hind wings having been modified into the tiny, drumstick-like halteres, which provide balance in flight.

Scathophaga stercoraria, competing males
Stand off – two competing Scathophaga stercoraria males face each other as they await the arrival of a female.

Scathophaga stercoraria, mating pair
Scathophaga stercoraria, mating pair. The female is somewhat duller in colour, with more pronounced greenish tinges. Note especially the lack of bright orange-yellow fur on the front legs.

Photographs: on pony dung, Wicken Fen, Cambridgeshire, September 2004.

© A.J. Silverside
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