Nanna fasciata (Meigen, 1826)

N. fasciata and N. tibiella are very similar. Collin (1958)[1] points out that they were previously separated by the colour of the femora, with those of N. fasciata having a yellowish base and tip, whilst N. tibiella has entirely dark femora. He reports that this is not a reliable character (and I agree!). However, it is nevertheless useful to note that the legs of N. fasciata do generally appear lighter (and N. tibiella tends to have darker tarsi too), therefore it is a useful way of pre-sorting a mixed batch prior to detailed checking. Wing length: ♂ 3.5 - 3.8 - 4.0 mm (4); ♀ 3.8 - 4.4 - 5.7 mm (10).

References