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Sepsidae

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Classification

BRACHYCERA, Muscomorpha Schizophora Acalyptratae, Sciomyzoidea

Number of British species: 28

Size: S

Difficulty: 2

Scheme: Covered by the Sepsid Recording Scheme

Characters

Small to medium sized (2-6 mm), slender, ant-like flies with relatively few bristles or hairs. Body colour generally black, in some cases lustrous and/or with a distinct pattern of silvery pruinosity on the side of the thorax. In general, walking about on vegetation while waving their wings. An exception is Orygma luctuosum Meigen, a robust, hairy, somewhat flattened fly. The Sepsidae, including Orygma, are distinct from all other Acalyptrate flies on account of the presence of 1 or more bristles at the posteroventral margin of the posterior spiracle. Head rounded, arista bare; ocelli present; Ocellar bristles present; Postvertical bristles diverging or absent; 0-3 pairs of frontal bristles, if present curving outward or (obliquely) backward; interfrontal bristles absent, interfrontal setulae present in Orygma; vibrissae or vibrissa-like bristles usually present. Wing clear or tinged, often with a dark spot or clouding at the wing tip; costa continuous; vein Sc complete; crossvein BM-Cu present; cell cup closed. In the male femur and tibia of fore legs often with extrusions, spurs, teeth and the like. Tibiae usually with dorsal preapical bristle, but in several genera small or absent (e.g. Meroplius, Nemopoda, Themira).

Biology

The larvae of most Sepsidae largely develop in dung, excrement, rotting organic matter such as dead snails and insects, mushrooms and bracket fungi, in nests of birds, in soil rich in organic compounds, in compost, etc. The adults are generally observed near the larval habitats, usually in somewhat open habitats such as meadows, along watercourses, forest margins and clearings in woodland areas. Some species occur in major swarms on low vegetation and shrubs, waving their wings. These swarms can persist for over a month and are often accompanied by a certain odour. All this does not account for Orygma luctuosum which is a seaside species, to be found under cast up seaweed.

Identification

 
families/brachycera/acalyptrates/sepsidae.txt · Last modified: 2008/10/28 19:01 by schultmay     Back to top
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