They feed on soft-bodied organisms from which the body fluids are extracted by crushing and masticating the prey with labella at the apex of the proboscis. The larvae inhabit a range of wet substrates including mud, soil and rotting wood, and like the adults are carnivorous except for a few species which are phytophagous, developing in the stems of plants. The pupal stage is spent in a cocoon constructed by the final larval instar from detritus held together by a secretion of the labial glands.
Respiration is aided by respiratory horns projecting through the wall of the cocoon.
Aphrosylus are restricted to the intertidal zone of the seashore. Movements of adults are determined by the tides as the flies search solid, wet substrates for prey, following the ebb to low water and retreating with the flood, eventually to seek refuge in the splash zone at high water. Aphrosylus celtiber and the less common raptor are the largest, both 5-6 mm in length, whilst Aphrosylus ferox and mitis are much smaller, rarely exceeding 1.5 mm. Aphrosylus as a genus can be recognised by the distinctive enlarged and flattened silvery palpi projecting from the mouth edge reflecting the light as the flies run over the rocks. However separation of the individual species, celtiber from raptor , and ferox from mitis , requires microscopic examination to determine the small morphological differences between the species.