Colletidae

Colletidae is a family of bees, and are often referred to collectively as plasterer bees, due to the method of smoothing the walls of their nest cells with secretions applied with their mouthparts; these secretions dry into a cellophane-like lining. There are 5 subfamilies, 54 genera, and over 2000 species, all of them evidently solitary, though many nest in aggregations. Two of the subfamilies, Euryglossinae and Hylaeinae, lack the external pollen-carrying apparatus (the scopa) that otherwise characterizes most bees, and instead carry the pollen in their crop. These groups, and in fact most genera in this family, have liquid or semi-liquid pollen masses on which the larvae develop.

They can be found all over the world, but the most species live in South America and Australia. Over 50% of all bee species living in Australia belong to this family. Only the genera Colletes and Hylaeus can be found in Europe, while in North America there are, in addition to these two, the genera Caupolicana, Eulonchopria, and Ptiloglossa.

Traditionally, it has been believed that this family is likely the most "primitive" among extant bees, based primarily on the similarities of their mouthparts (the unique possession among bees of a bilobed glossa) to those of Crabronidae (the putative ancestors of bees), but recent molecular studies have disproved this hypothesis, placing Melittidae (sensu lato) as the basal group of bees.

"Nocturnal" species
The Colletidae is one of the four bee families that contains some species that are crepuscular (of both the "vespertine" and "matinal" types). These bees, as is typical in such cases, have greatly enlarged ocelli. The other families with some crepuscular species are Andrenidae, Halictidae, and Apidae.