In the field it rather resembles B. johannis in having a rather well-defined dark wing stigma, a wing length of about 6mm, and males with a black-haired thorax and abdomen. 

Examination of the antennae will quickly distinguish it from johannis and all other Bibios because it typically has only 5 flagellar segments (occasionally 6) and these are larger and less compressed than those of other species. The thorax is also more shiny, lacking the shagreened zones of johannis, and the hind tarsi of both sexes are narrower with the male hind basitarsis unswollen.

Unless identified by a recognised expert, a photo is required, and the specimen should be examined with a microscope. In the comments box, state the key or ID method used and describe the size and identifying characters.

Often in damp and well vegetated areas.

May and June.

A widespread and fairly common Bibio, especially in the north and west where it can be the most abundant species.

Rarely recorded in Leicestershire and Rutland.