Is the conspicuous flag-waving behavior in Anisoscelis alipes (Hemiptera:Coreidae) a social signal?

Exaggerated traits and conspicuous behavior are often assumed to act as social signals, yet some highly ornamented signals have been shown to primarily function in non-social contexts. The matador bug, Anisoscelis alipes (Hemiptera:Coreidae), has large brightly-colored tibial expansions of its hind legs which are used to perform a stereotypic ‘waving’ behavior, the function of which is unknown. If this phenotype functions primarily as a sexually selected signal, we predicted they would be sexual dimorphic both in morphology and behavior, as well as exhibit positive size allometry. Alternatively, if traits function as non-sexual social signals, the frequency or rate of flag-waving should increase with proximity to conspecifics regardless of sex. Morphologically, we found that both males and females exhibited hind leg expansions, which scaled isometrically with body size. Behaviorally, in experimentally constructed social groups we documented 318 bouts of leg waving with 745 instances of leg-waves. We found no difference in the overall number of waves or the rate of waving between males and females. Further, the sex of individuals in the immediate social environment did not alter the number or rate of leg-waving. In contrast to both sexual and social selection hypotheses, our results reveal that the exaggerated morphology and leg-waving behavior in the matador bug is not sex-specific and occurs more frequently as individuals become further away from each other. The function of leg-waving in A. alipes remains unconfirmed; however, our findings and observations strongly hint at a potential anti-predator function which merits testing in future studies.