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.
[1] The Andrenidae 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.
In the Andrenidae, such species occur primarily in the subfamily Panurginae.