Evylaeus nigripes (Lep.) is a large, polylectic social halictine bee, common in the Mediterranean region. Haplometrotic and pleometrotic nests are established late in spring and clusters of from 6 to 15 cells are constructed and surrounded by a cavity. A summer brood of small females and a few males emerges from these cells in July. The summer females behave as workers; they remain in their mother’s nest, assist in the construction of a deeper and larger cell cluster, forage for pollen and nectar, but do not guard the nest. They show some ovarian inhibition in a matrifilial society but become egglayers in queenless nests or when establishing their own burrows. They are much shorter-lived than their mothers, require no diapause, and are unattractive to the summer males. The social level of E. nigripes is comparatively high; summer males are less than 5% of the total brood. Queen and workers are relatively distinct morphs, although caste determination can be influenced by environmental factors. Sphecodes alternatus Smith is its specific parasitoid whereas several bombyliids, mutillids, and conopids attack E. nigripes as part of a much wider range of hosts.