The indestructible insect: Velvet ants from across the United States avoid predation by representatives from all major tetrapod clades

Abstract

Velvet ants are a group of parasitic wasps that are well known for a suite of defensive adaptations including bright coloration and a formidable sting. While these adaptations are presumed to function in antipredator defense, observations between potential predators and this group are lacking. We conducted a series of experiments to determine the risk of velvet ants to a host of potential predators including amphibians, reptiles, birds, and small mammals. Velvet ants from across the United States were tested with predator's representative of the velvet ants native range. All interactions between lizards, free-ranging birds, and a mole resulted in the velvet ants survival, and ultimate avoidance by the predator. Two shrews did injure a velvet ant, but this occurred only after multiple failed attacks. The only predator to successfully consume a velvet ant was a single American toad (Anaxyrus americanus). These results indicate that the suite of defenses possessed by velvet ants, including aposematic coloration, stridulations, a chemical alarm signal, a hard exoskeleton, and powerful sting are effective defenses against potential predators. Female velvet ants appear to be nearly impervious to predation by many species whose diet is heavily derived of invertebrate prey.

Keywords: Hymenoptera; Mutillidae; antipredator; predator avoidance; predator–prey.

Figure 1

Photos of the various species of velvet ants tested with multiple predators in this study. Dasymutilla occidentalis and Dasymutilla vesta occur in the Eastern United States (Eastern mimicry ring), while the remaining species occur in the Western United States and are part of the Western mimicry ring

Figure 2

(left) Photograph of the feeding station with a mockingbird (Mimus polyglottos) perched on top. Photograph by Richard Vaupel (used with permission). (middle) Painted mealworms used to test the role of aposematic coloration found in Dasymutilla occidentalis during interactions with free‐ranging birds. (right) Photograph of an aposematically painted mealworm that was struck at by a mockingbird and “decapitated” but not consumed