The tactile communication between the symbiotic goby Cryptocentrus steinitzi and its burrowing shrimp partner Alpheus purpurilenticularis was investigated by film analysis. Warning signals of the goby which elicit the retreat of the shrimp into its burrow consist mainly of rapid fin flicks transmitted to the shrimp through its long antennae. Five different parameters of the structure of the warning signal were analyzed. The effect of various variables on the response of the shrimp and its latency were examined with a stepwise multiple regression analysis. Feedback mechanisms involved in this communication system are described. The evolution of the tail flick warning signal and a model describing the relationship between the main elements involved in the generation of warning signals are discussed.