The term 'sociality' describes a broad spectrum of behaviours in bees. It ranges from non-social, solitary species, through to species which share entrances to individual nest chambers, and finally to advanced social organisations consisting of very large colonies with many thousands of members.
Assigning bees to one particular category can be difficult, especially because bee species from the same genus may nevertheless vary in their degree of sociality.
In 2021, work by Da Silva1 [citing Cowan (1991), Wilson, (1971); Michener, (1974); Eickwort, (1981)] provided useful definitions of the different levels of social organizations of the insect order, Hymenoptera as follows:
Note that all bees exhibiting social behaviour fit into the category of 'social', but the term 'social bee' can be further divided into different forms of sociality.
For further information, see my page about eusociality.
Within his paper, Da Silva further assigned a number of bee species to their specific group within the above defined sociality definitions.
It's interesting that many bees which tend to be labelled as 'solitary' actually demonstrate at least some form of sociality.
Furthermore, a whole genus cannot be assigned to one definition of sociality. It's apparent that the behaviours of each specific species needs to be considered.
It is perhaps fair to note that species are sometimes assigned to a particular genus at discovery, only to be switched to a different genus later, which can even result in a name change.
In a similar fashion, as investigation into bees develops further, the ways in which we assess them may change as our knowledge bank increases in depth and vigor.
It is also the case that scientists may not always agree about how bees are classified.
It is beyond the scope of this page to list every species mentioned, however, for illustrative purposes, some examples mentioned by Da Silva are as follows:
Examples Of Primitively Eusocial Bees
1. da Silva J (2021) Life History and the Transitions to Eusociality in the Hymenoptera. Front. Ecol. Evol. 9:727124. doi: 10.3389/fevo.2021.727124