Eusocial insects of the order Hymenoptera display reproductive division of labour, whereby offspring are born to reproductive individuals but cared for by others (‘workers’) in a colony. A new transcriptomics study implicates insulin signalling as a mechanism underlying the evolution and regulation of this social behaviour.

Looking at seven different ant species, including queen-less species, the authors compared gene expression in whole brains or heads of reproductive ants with those of worker ants. The expression of one gene, insulin-like peptide 2 (ilp2), was consistently upregulated in reproductive animals.

To investigate the role of ILP2, the team used the clonal raider ant Ooceraea biroi, a queen-less species in which workers reproduce asexually and whose colonies alternate between brood-care and reproductive stages. The brood-care phase begins when larvae hatch from eggs, as the larvae suppress reproduction and induce brood care in adults. The reproductive phase begins when the larvae pupate, upon which all workers produce eggs through a type of parthenogenesis.

ILP2 protein was found exclusively in the brain of O. biroi. Removing larvae from colonies in the brood-care phase increased ilp2 expression, whereas adding larvae in the reproductive phase decreased ilp2 expression, in brains of adults. Injecting synthetic ILP2 into adults in the presence of larvae strongly activated ovaries, thus overriding inhibitory larval signals.

These findings, as well as previously reported functions of ILP2 in larval growth, metabolism and reproduction in other organisms, strongly support a role for this protein in reproductive potential.