Observations of the recruitment behaviour ofPheidole within the nest reveal the existence of a complex behavioural mechanism which operates in the recruitment of nestmates, including the soldiers, to mass foraging. Highly excited recruiters, arriving at the nest, perform, in addition to trail-laying, a motor recruitement display comprising running, accelerated antennal beatings and body oscillations. While moderately excited recruiters perform this display only on encounters with soldiers, highly excited recruiters display it also on encounters with workers. The release of the motor display appears to be influenced by the attractiveness of the food on one hand, and the mechanical stimulation received from the partner, on the other. The scent trail and the motor display acting together are far more effective than the quiet scent trail recruitment. During the later stage of the experiment, when the reaction of the workers to the recruiting stimuli has already weakened considerably, the motor display still brings about recruitment. The motor display is a highly exciting factor, arousing ants from the resting to the active state. This form of alert is particularly important in the recruitment of soldiers. The formation of recruitment depends on both the number of recruiters and the character of the recruiting performance. The releasing value of the recruiting stimuli decreases with time, as habituation increases. This process, together with excess recruitment, constitues a mechanism which controls the level and limits of recruitment and determines the time of its termination.