ABSTRACT.The complex system of alarm communication inOecophylla longinodais described. The mandibular gland secretion of major workers releases in other major workers a complex pattern of behaviour, which includes components of alerting, attraction and biting. The main constituents of the secretion are hexanal and 1‐hexanol, which release alerting and attraction respectively. Of the thirty or so trace components, at least two, 2‐butyl‐2‐octenal and 3‐undecanone, act as markers for attack. In combination, these components produce a sequential message in space and time, dependent on their relative proportions, volatilities and threshold concentrations for behavioural