The insect order Hymenoptera (including ants, bees, and wasps) used to be considered the model of nonhuman sociality. The famous ecologist (and one of my personal academic crushes) E.O. Wilson used ants as a model for understanding how sociality evolves. In a talk he recently gave at my uni, he explained that understanding sociality in other organisms is the first step toward understanding it in ourselves, which then allows us to approach the questions: why are we here? where did we come from? where are we going?
But sociality, like all things, exists on a gradient. From what we consider to be “true sociality” (or eusociality) all the way to solitary, with everything in between. Scientists have struggled to provide precise definitions of each level of sociality, but exceptions and strange things inevitably confound attempts to do so comprehensively.
In my opinion, bees are a great system for studying sociality because they exist at all of these different levels. There are solitary bees and eusocial bees, communal and semisocial bees, bees that form dense aggregations and bees that lay a single egg inside a single nest cell in the pith of a reed.
I should state that I am biased toward bees. I love them and although that hurts my impartiality as a scientist, there it is. I am but human.
Without exhaustively addressing the different stages of sociality and the respective phylogenetics of such, I would like to present to you a communal genus of bee: Agapostemon.
This genus is North American in distribution, and it is especially notable for its beauty: iridescent green thoraxes, often with yellow and black bands on the abdomen. Sometimes the females are iridescent all over.
Agapostemon species are communal because each nest is solitary but the nests exist in aggregations. Bee scientist Laurence Packer says, “Semisocial is a reproductive division of labour among individuals of the same generation, communal is nest sharing with each individual acting as if solitary within the nest – i.e. digging, provisioning and ovipositing in their own brood cells.
Of course, how much interference and cheating there may be in such “communal” nests is largely unknown. Though reports of fights at nest entrances, rather than welcoming “with open arms” (or more accurately open mouthparts to permit food exchange as is known for Australian communal bees – Kukuk papers), have been made but not, to my knowledge, studied in any detail.”
My friend found these nests in his yard. There are four entrances, so there is an aggregation, but a different bee guards each nest, so they are communal, not semisocial.