Anasimyia transfuga (Linnaeus, 1758)
This species was confused with A. contracta before the review by Claussen & Torp (1980); older records are therefore suspect unless a specimen has been re-examined.
Biology & ecology:
Confusion with A. contracta, means that it is not certain to which species larval descriptions under this name in earlier literature apply. Adults are found in wetland margins where decaying vegetation is abundant, and tall emergent vegetation such as Sea Club Rush Scirpus maritimus, Branched Bur-reed Sparganium erectum or Reed Sweet Grass Glyceria maxima occurs. This species will tolerate smaller and more shaded water bodies than those typically favoured by other members of the genus, occurring for example in ditches beside woodland rides.
Most records are southern and there are very few recent records north of Kendal. This is a lowland species that is most likely to be encountered in coastal marshes and wet river valleys.
Status & conservation:
In common with others in this genus, there has been a very strong downward trend in occurrence since the 1980s.