The exoskeleton of all velvet ants is unusually tough (to the point that some entomologists have reported difficulty piercing them with steel pins when attempting to mount them for display in cabinets). This characteristic allows them to successfully invade the nests of their prey and also helps them retain moisture. Like related families in the Vespoidea, males have wings, but females uniformly are wingless. They exhibit extreme sexual dimorphism. The males and females are distinct enough in their morphology, often making it very hard to decide whether or not a given male and female belong to the same species, unless they are captured while mating. In a few species, the male carries the smaller female aloft while mating, which is also seen in the related family Tiphiidae.