One species is unique for having both social and asocial populations, Ceratina australensis, which exhibits all of the pre-adaptations for successful group living.

Social colonies in that species consist of two foundresses, one contributing both foraging and reproductive effort and the second which remains at the nest as a passive guard.

[3] Ceratina are commonly dark, shining, even metallic bees, with fairly sparse body hairs and a weak scopa on the hind tibia.

They are very commonly mistaken for "sweat bees" (family Halictidae), due to their small size, metallic coloration, and some similarity in wing venation; they can be easily separated from halictids by the mouthparts (with a long glossa) and the hindwings (with a tiny jugal lobe).

[4] 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,[5] but males guarding nests and mating with females has been documented in other species (e.g., Macrotera portalis[6]).