Intraspecific visual signaling by praying mantis nymphs

Nymphs of some hymenopodid mantids use a repertoire of stereotyped movements of the brightly colored prothoracic legs, distinctively marked abdomen, and antennae during encounters between conspecifics. Nymphs do not signal to size and color-matched heterospecifics, other insects, or models. Covering the compound eyes eliminates the species-specificity without affecting the signaling itself (elicited by touch in these experiments). The types and patterns of movements follow an ontogenetic progression that parallels the marked changes in body form across the nymphal stages. In the older nymphs, the leg and abdomen movements begin to resemble components of the adult defensive display. However, adults of the species studied did not use visual signals in intraspecific encounters. We found no indication that visual signals mediate aggressive hierarchies or territorial defense, suggesting instead a system for averting potentially damaging fights. Juveniles of these species are remarkable for the absence, even under crowded conditions, of the cannibalism that is the norm for praying mantis nymphs in lab and possibly field settings.