Halictidae is a cosmopolitan family of the order Hymenoptera consisting of small to midsize bees which are usually dark-colored and often metallic in appearance. Several species are all or partly green and a few are red; a number of them have yellow markings, especially the males, which commonly possess yellow faces, a pattern widespread among the various families of bees. They are commonly referred to as sweat bees (especially the smaller species), as they are often attracted to perspiration; when pinched, females can give a minor sting.
Most halictids nest in the ground, though a few nest in wood, and they mass-provision their young (a mass of pollen and nectar is formed inside a waterproof cell, an egg laid upon it, and the cell is sealed off, so the larva is given all of its food at one time, as opposed to "progressive provisioning", where a larva is fed repeatedly as it grows, as in honey bees). All species are pollen feeders and may be important pollinators.
Many species in the subfamily Halictinae are eusocial at least in part, with fairly well-defined queen and worker castes (though not the same as the caste system in honey bees), and certain manifestations of their social behavior appear to be facultative in various lineages.
Several other genera and species of halictids are cleptoparasites of other bees (mostly other halictids), and the behavior has evolved at least nine times independently within the family. The most well-known and common are species in the genus Sphecodes, which are somewhat wasp-like in appearance (often shining black with blood-red abdomen, usually 4-9 mm in body length); the female Sphecodes enters the cell with the provision mass, eats the host egg, and lays an egg of her own in its place.
The Halictidae is one of the four bee families that contains some species that are crepuscular; these halictids are active only at dusk or in the early evening, and therefore technically considered "vespertine". These bees, as is typical in such cases, have greatly enlarged ocelli. The other families with some crepuscular species are Andrenidae, Colletidae, and Apidae.
List of North American genera
- Family Halictidae Large format diagnostic photos, information.
- Everything About the Sweat Bee - Description and photo of the sweat bee.
- Image Gallery from Gembloux