Flag-waving behavior in matador bugs is an antipredatory strategy

To dissuade predator attack, animals may advertise their chemical defense with bright coloration and specialized behaviors. However, these antipredator adaptations can be costly, if they unnecessarily draw attention to the prey animal. Thus, animals with elaborate antipredator traits may be under pressure to selectively increase advertisement of their defenses in particular contexts. The matador bug, Bitta alipes (Hemiptera: Coreidae), possesses large, colorful flags on its hind tibia that it uses in a stereotypic "waving" behavior. Previous research found no evidence that this waving behavior is employed in social or sexual interactions. Here, we experimentally tested for a potential antipredator function of flag waving by exposing a matador bug to either an arthropod predator (praying mantid) or a similarly sized nonpredatory arthropod (nonpredatory katydid). In total, we recorded 2,938 leg waves among 25 individuals. We found that matador bugs' waving behavior increased in duration, frequency (number of wave bouts), and intensity (number of waves per bout) in the presence of praying mantids. Notably, we found on average a 7-fold increase in the number of waves in the presence of a mantid relative to a similarly sized nonpredatory arthropod. Praying mantids consumed very few matador bugs (3/25) and never attacked bugs that were waving, lending support to the hypothesis that flags serve an antipredator function in matador bugs. We find similar flag-waving behavior in at least 5 closely-related flag-legged bug species, all of which have expanded tibial flags with contrasting coloration and are Passiflora specialists, providing opportunities for future studies to examine the evolution of elaborate flag-waving behavior as an antipredator behavior in this group.