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Bibionidae - St Mark's Flies, Feverflies



NEMATOCERA, Bibionomorpha, Bibionoidea

Number of British species: 20

Size: S-L

Difficulty: 1-3


Small to large (2-15 mm), robustly built Nematocera. Usually densely set with fine hairs; body colour pale brown to black, in some cases (partially) red or yellow. Ocelli conspicuous; in male eyes holoptic and consisting of two separate parts, in female eyes dichoptic and simple; antenna inserted rather low, with 6-12 segments. Wing wide, with distinct anal lobe; wing clear or darkened. Tibia of fore leg usually swollen, in Bibio with a long, stout spur and an apical projection; in Dilophus with several rows of short, stout spurs.


The larvae are largely found in the topsoil of moist grasslands and woodland and in decaying wood. They appear to feed mainly on rotting plant matter; in some cases also on living roots or stems, thereby causing damage to valuable crops that can be substantial if they are present in large numbers. Densities up to 37,000 larvae per square metre have been recorded. The adults are mainly found in spring, usually present for only a few weeks every year, sometimes in very large numbers. The males often fly or hover together in swarms. The adults, those of Dilophus in particular, often visit flowers as well.


families/nematocera/bibionidae.txt · Last modified: 2008/05/24 17:00 (external edit)     Back to top
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