Adults: Small to medium flies (5-10 mm); moderately robust (especially for lower Diptera), black, shiny and usually densely pilose (hairy). Males holoptic (eyes making up most of the head and meeting in the center); females are dichoptic (eyes are separated). Antennae short. Fore femora with large, produced spines. Larvae: Eucephalic, holopneustic larvae lacking true legs or prolegs; usually covered in small spines or processes.