Nestmate recognition in the ant Formica argentea

In eusocial insects recognition of group membership is an essential component of evolutionary success. In most cases recognition of membership is mediated by differences in the surface chemistry between members and non-members. Although numerous studies focus on identifying surface chemistry, very few have successfully made the link between chemistry and behavior, a connection that is essential when investigating nestmate recognition in social insects. Here we investigate insect surface chemistry and its direct effects on behavior in the ant Formica argentea. We found that the cuticle of F. argentea contains 23 different hydrocarbons composed of alkanes, alkenes, and methyl-branched alkanes. Generally all workers contain the same compounds on their cuticles but vary in relative proportion between workers from different nests. F. argentea workers can be correctly classified as nestmates statistically based on hydrocarbon profile however we found that not all the compounds present on the cuticle are responsible for eliciting behavioral responses. Alkenes caused aggression between pairs of ants while alkanes did not elicit any noticeable behavioral responses. Our study suggests that cues eliciting nestmate recognition in social insects come from specific compounds on the cuticle rather that the entire cuticular profile.