The Andrenidae are a large, nearly cosmopolitan (absent in Australia), nonparasitic bee family, with most of the diversity in temperate and/or arid areas (warm temperate xeric). It includes some enormous genera (e.g., Andrena with over 1300 species, and Perdita with nearly 800). One of the subfamilies, Oxaeinae, is so different in appearance that they were typically accorded family status, but careful phylogenetic analysis reveals them to be an offshoot within the Andrenidae, very close to the Andreninae.
They are typically small to moderate-sized bees, which often have scopae on the basal segments of the leg in addition to the tibia, and are commonly oligolectic (especially within the subfamily Panurginae). They can be separated from other bee families by the presence of two subantennal sutures on the face, a primitive trait shared with the sphecoid wasps. Many groups also have depressions or grooves called "foveae" on the head near the upper margin of the eyes, another feature seen in sphecoids, and also shared by some Colletidae. Andrenids are among the few bee families that have no cleptoparasitic species. There are also a very large number of taxa, especially among the Panurginae, whose sting apparatus is so reduced that they are effectively unable to sting.
Andrenidae are one of the four bee families that contain some crepuscular species; these species are active only at dusk or in the early evening, and therefore technically considered "vespertine". In the Andrenidae, such species occur primarily in the subfamily Panurginae. These bees, as is typical in such cases, have greatly enlarged ocelli, though one crepuscular subgenus of Andrena has normal ocelli. The other families with some crepuscular species are Halictidae, Colletidae, and Apidae.
- C. D. Michener (2007) The Bees of the World, 2nd Edition, Johns Hopkins University Press.
- Andrena Image Gallery from Atlas Hymenoptera
- North American Andrenidae
- Identification guides to eastern North American Andrenidae