Colletes (plasterer bees or cellophane bees) is a large genus of smallish and hairy ground-nesting bees of the short-tongued bee family Colletidae. They have an almost worldwide distribution, but occur primarily in the Northern Hemisphere where they are found almost everywhere up to the edge of the Arctic ice.
These bees were traditionally held to be a very ancient lineage, but as has more recently turn out their primitive traits are simply retained from ancestral bees. there were about 470 described species, and an estimated total around 700. They occur throughout the world except in Antarctica, Australia, Madagascar, and Southeast Asia. There are about 60 species in Europe and about 100 in North America north of Mexico. Due to their breeding habits, they require soils that are somewhat sandy and not too humid; the bulk of their diversity is found in temperate to subtropical Asia, in particular Central Asia. Since their relatives are found mainly in the Americas and Australia, the high diversity of Colletes in Asia is probably secondary and fairly recent, with the genus most likely originating in tropical America perhaps as much as 50 million years ago, and diversifying abundantly in the highly continental climate they found in interior Eurasia.
Most Colletes species are somewhat similar to a diminutive honey bee. They are typically some 1-2 cm long as adults, with large vertical compound eyes, and usually have a dense coat of whitish, light grey or yellowish-brown hair on their thorax and head; almost all have light hairy bands on the end of the major segments of the abdomen upperside. Their antennae are moderately long by bee standards, and gently curved. From other short-tongued bees they can be distinguished by having a two-lobed tongue, the posterior part of the second recurrent wing vein forming an outward bow, as well as the shape of the first abdominal segment (propodeum). The latter has a longitudinally crested short subhorizontal to vertical basal zone in Colletes bees, which in most species abruptly ends with a crosswise ridge or break in slope.
They tend to be solitary, but sometimes nest close together in aggregations. The females collect pollen for their offspring with the hindlegs and the bottom of the propodeum. Despite being small and solitary, Colletes bees may be keystone pollinators and some are economically important as pollinators of fruit trees, green manure plants, or fruiting Ericaceae; most species are at least somewhat specialized as regards the flowers they visit, and some (such as the ivy bee) preferentially forage on one or very few plant species. Species in the genus have no separate worker caste, each mature female build cells in her own underground nest and lines them with a cellophane-like plastic secretion. This is a true polyester mostly consisting of polymerized 18-hydroxyoctadecanoic acid and 20-hydroxyeicosanoic acid which is applied to a matrix of silken threads, earning them the nickname polyester bees. Colletes nests are attacked by parasites such as Stenoria beetles, and particularly cuckoo bees of genus Epeolus, whose females have specialized abdominal cutting spines for slicing open the protective polyester coating to deposit their eggs. Males of some Colletes are the only pollinators of certain Ophrys orchids, whose flowers look and scent mimick the bees' females.