100: Velvet Ants

Not velvet. Not an ant.

Velvet ants are not ants at all – they are wasps from the family Mutillidae, which contains about 8000 species, all characterized by dramatic differences in appearances and life cycles for males and females. While the males are winged, with smooth bodies, the females are wingless and resemble large, hairy ants (see illustration of a female below). Aside from mating, and unlike actual ants, velvet ants lead solitary lives. The females spend most of their time walking around, looking for a suitable place to lay their eggs – inside the pupae of other ground-dwelling insects, such as ground nesting wasps.

Since the velvet ants will only lay a single egg inside of a pupae, they have an especially tough task to wander around searching for appropriate places to act as a parasite. Crawling on the ground in the open without wings to fly away, the females have evolved to have several layers of protection. First of all, they can signal warnings to predators: they are brightly colored (see below), squeak loudly when threatened, and have a distinctive chemical smell. If all of that fails, they also have an incredibly tough exoskeleton, and their bodies are rounded in such a way that it is difficult for most predators to get a grip on them. Their final line of defense is their highly evolved ovipositor, which doubles as a painful stinger. The velvet ant has limited venom; instead, the sting is designed to shock a predator and make an escape. According to the London Natural History Museum,

“No animal living today is known to specifically target velvet ants, but a 2018 paper found that female velvet ants are 'nearly impervious' to attacks by a variety of insectivores. In over 100 observed interactions between velvet ants and potential predators (including toads, lizards and shrews), only one wasp was successfully consumed… To test the effect of velvet ants' colours on predators, scientists carried out experiments with birds where some mealworms were painted red and black to look like the wasp Dasymutilla occidentalis. These were left uneaten by the birds, whereas tan-coloured mealworms were all consumed immediately. When a live velvet ant was served, the birds appeared hesitant to visit the feeder at all.”

There are around 80 species of velvet ant found in Colorado, most in open grasslands on the Eastern Plains and the Western Slope.