Velvet ants (family Mutillidae) are not ants (family Formicidae); they're more closely related to wasps. Their common name comes from the velvety appearance created by the short, densely spaced hairs that cover the entire bodies of both the males and females. Males have wings and are good flyers, while the females lack wings. Female velvet ants are solitary and may be found crawling across the ground. They look like hairy ants; however, unlike our native ants, velvet ants have a functional stinger.
There are a number of species of velvet ants in the U.S. with most species living in the desert southwest. All species are brightly colored, presumably to advertise their stinging personality. The species most commonly encountered in Ohio is Dasymutilla occidentalis. Measuring around 3/4" in length, this is one of the largest velvet ants found in the world. Owing to their size, this velvet ant packs a stinging punch similar to that of a baldfaced hornet. In fact, their painful sting is responsible for their alternate common name of the "cow killer ant." However, it is speculated that this intimidating common name is less associated with the potential for these wasps to lay-low bovine, and more likely associated with the painful surprise when someone gets stung by one of these "ants". There are no records of these wasps ever killing cow.
Cow killers range in color from deep red to orangish-red. Their legs are shiny black and they have a black transverse band across their abdomen that is connected by a thin longitudinal black band to a "black belt" at the constriction between their abdomen and thorax. Like all velvet ants, the cow killer lays its eggs on the larva of a ground nesting bee or wasp. Their favorite menu item is the larvae of the CICADA KILLER WASP (Sphecius speciosus). Once the cow killer female locates a cicada killer's burrow, she digs into the larval chambers and lays a single egg next to each wasp larva. Once the eggs hatch, the cow killer's larvae consume the cicada killer's larvae. Cicada killer populations were very high last season in Ohio, particularly in the southwest part of the state, as they are again this season (BYGLs 2012-18, 08/02/12; 2013-16, 07/18/13). Consequently, cow killer populations appear to be unusually high this season and they have an abundance of food for a new generation.