Chemical recognition of reproductive status in social insects

Inclusive fitness theory explains how helpers reproduce indirectly via the breeders they help. The inclusive fitness helpers get depends on their relatedness to the breeder(s), colony productivity and fertility of the breeder(s). It is therefore critical for workers to assess breeder fertility. There is strong evidence that, in wasps, bees and ants, the cuticular hydrocarbon (CHC) profiles of breeders are a signal of fertility. Chemical and behavioural evidence suggests that linear alkanes are not involved in communication, whereas methyl-branched alkanes and alkenes may constitute, or at least contribute to, the fertility signal. The correlation between CHCs and reproduction is well established, as well as the fact that CHCs are detected and that workers react accordingly. However, whether CHC profiles are honest is yet to be demonstrated. Hormonal and genetic studies, such as inactivating genes regulating the production of alkenes, are promising approaches to investigate the honesty of CHC profiles.