Critter Corner
The Preservation News. November. 1999
© 1999

by LeCnny Vincent

The Velvet Ant.

I saw my first velvet ant many years ago. It looked like a large, compact ant covered in rich, straight-out red velvet. It was beautiful, and I was tempted to pick it up. Then, at the last minute, I remembered its common names, "cow killer" or "mule killer," referring to its extremely painful sting! Not too surprising, maybe, as the velvet ant is actually a wasp.

Ants, bees and wasps belong to the Hymenoptera. This order contains many beneficial insects that pollinate our crops and native plants, and eat or parasitize pest insects. Ants have knobs on their narrowed waist (the section that joins the thorax to the abdomen), bees have feathery hairs all over their body, and wasps have neither a knobbed waist nor feathery hairs. Velvet ants belong to the wasp family Mutillidae and can be referred to as mutillids or, as an individual, a mutillid. Only female wasps can sting.

Adult velvet ants are usually brightly colored. They can be deep red, orange, or yellow. Occasionally I have found white ones. Often you can see black bands encircling the abdomen. Mutillids are hard to identify in the field because a given species may take various color forms in different areas. There are over 500 species in America north of Mexico, mostly in the South and West. Adults are 5 to 20 mm (about 0.25 to 0.80 inch) long. Females are wingless, males are winged and usually larger. Some species make a squeak (stridulate) when disturbed.

Velvet ant larvae are external parasites on the larvae and pupae of solitary bees and wasps that live in underground burrows. A few species parasitize beetle and fly larvae. Adult female velvet ants search on foot for sandy areas, their preferred habitat, to locate the underground nests of their hosts. If the wasp or bee nest is sealed, the velvet ant will chew its way in. Once inside, the female finds each helpless cocoon, bites a small hole through the cocoon wall, and inserts a single egg on the developing bee or wasp. She then plugs up the hole using a mixture of salivary secretions and sand and departs to search for more burrows to infiltrate. Soon her eggs hatch, and the white legless velvet ant larvae slowly consume their hosts.

Adult velvet ants apparently are not host specific. An individual mutillid may attack wasps or bees that belong to different genera or even families. Some species of velvet ant have been observed attacking full-grown bees and wasps. The velvet ant bites a hole in the neck of its victim and sucks out the body contents. Velvet ants have an unusually thick exoskeleton, a suit of armor, that probably serves to protect them from the stings and powerful bites of nest-defending bees and wasps.

Velvet ants are easily found walking in areas where their hosts nest. These are often open, arid sandy areas. I have seen velvet ants walking on trails in Laguna Coast Wilderness Park from February to October, usually in the afternoon. Their bright colors, which make these insects highly conspicuous and memorable, are probably warning signals (called "aposematism") for potential predators such as birds, lizards and unsuspecting humans. Potent stings, like those of the diminutive cow killer, are not soon forgotten.

Lenny Vincent teaches biology at Fullerton College and is on the Board of Directors of the Laguna Greenbelt, Inc.