Ceratina
The cosmopolitan bee genus Ceratina, often referred to as small carpenter bees, is the sole lineage of the tribe Ceratinini, and is not closely related to the more familiar carpenter bees. The genus presently contains over 300 species in 23 subgenera. They make nests in dead wood, stems, or pith. Although they were considered as mostly solitary in the past, there is growing evidence that many species are facultatively eusocial.
Ceratina are commonly dark, shining, even metallic bees, with fairly sparse body hairs and a weak scopa on the hind tibia. Most species have some yellow markings, most often restricted to the face, but often elsewhere on the body. They are very commonly mistaken for "sweat bees", due to their small size, metallic coloration, and some similarity in wing venation; they can be easily separated from halictids by the mouthparts and the hindwings.
Behaviour
There can be multiple females in a single nest, where daughters or sisters may form very small, weakly eusocial colonies. In Ceratina nigrolabiata, a Mediterranean species, males may guard the opening to the nest of a female they hope to mate with, and are often not the father of the brood within the nest; this is the first bee species in which male nest-guarding has been classified as a form of biparental care, but males guarding nests and mating with females has been documented in other species.A few species of Ceratina are exceptional among bees in that they are parthenogenetic, reproducing without males. Parthenogenetic reproduction was genetically confirmed in Ceratina dallatorreana and it is presumed also in Ceratina parvula and Ceratina dentipes.