Anonymity and specificity in the chemical communication signals of social insects

Summary

The chemical communication signals of social insects, like many other insect semiochemicals, are complex mixtures that exhibit considerable variation in molecular composition and in the relative proportions of components. We propose that this variation is often functional, identifying individuals and groups on a variety of organizational levels and making possible a variety of adaptive discriminatory behaviors. Signals may be characterized as anonymous which are uniform throughout a group or organizational level, identifying the signaller as a member of the group but not distinguishing it from other members. Specific signals vary, and identify the signaller as an individual or member of a particular subgroup. These terms are relative; a given semiochemical may be anonymous in one context and specific in another. Specificity may be derived from the biosynthetic ‘noise’ in an anonymous signal by a process of chemical ritualization. Mechanisms for recognizing both anonymous and specific signals depend on their predictability; recognition of predictable signals may be encoded in a closed developmental program, while those that are unpredictable must be learned. These categories may be usefully applied to a broad range of interactions among social insects, including sexual communication, community structure, and nestmate and kin recognition.