Why does the Matador Bug, Anisoscelis alipes (Hemiptera: Coreidae), Wave its Brightly Colored Legs?

Many animals exhibit elaborate traits and conspicuous behaviors. Sexual or social selection are often drivers of extreme trait elaboration and signalling, but conspicuous traits may also serve non-social functions. The matador bug, Anisoscelis alipes (Hemiptera: Coreidae), has large, brightly colored tibial expansions on 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 aggressive signal, we predicted sexual dimorphism both in morphology and behavior, as well as positive size allometry. Alternatively, if these traits function as non-sexual social signals, both male and females may perform waving behavior, and the frequency or rate of flag-waving should increase with proximity to conspecifics. Against some of our predictions, we found both males and females exhibited hind leg expansions which scaled isometrically with body size. We recorded 745 leg waves among 12 individuals and 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 social environment did not predict the number of waves or rate of flag-waving. Sexual selection is often reported to be the main driver of many highly conspicuous traits, but our investigation of morphology, behavior, and natural history reveals little evidence for social or sexual selection as the primary driver of these conspicuous signals. We suggest future studies investigate a potential anti-predator function to explain the evolution of colorful and expanded tibial flags in other flag-legged bugs.