Abstract

Study of the visual displays of more than 30 species of crabs allows some generalizations on the Brachyrhyncha. The displays fall into two groups, the Lateral Merus and the Chela Forward. Each group contains three major subtypes of display, which originated as discrete signals of intensity. Several special ritualizations of the Lateral Merus have evolved in certain genera. The Lateral Merus seems to be the primitive type of display in the Brachyura and still exists in most crabs. It is speculated that the Chela Forward arose from a specialized courtship display but has been adopted for general agonistic use in some genera.