Information use in space and time: sex allocation behaviour in the parasitoid wasp Nasonia vitripennis.

Behavioural decisions require the appropriate use of relevant information about the environment. However, individuals may have imperfect information, imposing a constraint on adaptive behaviour. We explored how information use influences the sex allocation behaviour of the parasitoid wasp Nasonia vitripennis in response to local mate competition. Optimal sex ratios under local mate competition require females to estimate the number of other females that contribute eggs to a patch. Females rapidly changed their sex allocation in response to changes in the number of females in the environment, suggesting that they are not constrained by how quickly they can respond to new information. Furthermore, females also showed some response to olfactory cues that indicated oviposition by other females, suggesting that such indirect cues may be part of their information repertoire. Both the absolute and the relative size of the patch were important for sex ratio decisions, with sex ratios declining on larger patches in a way that suggests that large patches in effect become more than one patch, with females on larger patches allocating sex increasingly independently of other females. We conclude by highlighting variation among species in whether particular cues are used for sex allocation.