Task specialization influences nestmate recognition ability in ants

Insect societies are a paramount example of efficiency based upon division of labour. Social insect workers specialize on different tasks, such as brood care and foraging. This polyethism is underlined by the development of brain and olfactory organs. Nestmate recognition in ants is based on perception of chemical cues through olfaction; therefore, we asked whether task polyethism affects the ability of ants to discriminate friends from foes. We used the carpenter ant Camponotus aethiops to investigate the ability of three behavioural groups of worker (foragers, nurses and inactives) in recognizing intruders. Foragers, which are older workers mainly performing tasks outside the nest, showed higher levels of aggression towards intruders than nurses did. Foragers appeared to be more efficient at recognizing nonnestmate cues than did intra-nidal workers (nurses and inactives), and they possibly have higher motivation to attack. This suggests that ant workers change their olfactory sensitivity to non-nestmate stimuli during their life. This plasticity could be adaptive, as younger workers, who typically stay inside the nest, usually do not encounter intruders, while older workers have more experience outside the nest and differently developed neural circuits. A sensitive nestmate recognition system would thus be an unnecessary cost early in life.