One of the conditions favoring the evolution and maintenance of sociality is the ability to discriminate between kin and non-kin, because it allows altruistic acts to be directed to recipients of high relatedness (Hamilton, 1987). Nestmate recognition is the process whereby social insects recognize individuals belonging to their own colony or an alien colony, and accordingly allow or prohibit entry to their nest. Nestmate recognition often results in the discrimination of kin from non-kin, but in social insects there is a distinction to be made between nestmate and kin recognition. Where kin recognition is the assessment of the degree of relatedness towards another individual, nestmate recognition is the binary recognition of group membership (Arnold et al., 1996; Lenoir et al., 1999). In ants, wasps and termites, the blend of hydrocarbons present on the cuticle appears to comprise the essential compounds that serve as nestmate recognition cues (Howard and Blomquist, 2005), although in honeybees fatty acids and esters may also play an important role (Breed, 1998a; but see Dani et al., 2005; Ch?ine et al., 2005). At the end of the 1990s, the notion that cuticular hydrocarbons act as recognition cues was supported mainly by correlative evidence (Singer, 1998; Vander Meer and Morel, 1998; Lenoir et al., 1999), but significant progress has been made over the last decade.