Cow killers also are called velvet ants, and both names involve an element of inaccuracy. These 1-inch-long insects are not ants but small wasps. The extraordinarily painful sting of the female velvet ant has led to a false belief that a cow that is stung will perish from the pain. You can recognize velvet ants by their fuzzy coats. Despite their fearsome reputation, these wasps are non-aggressive. Pick up a female or step on her barefooted, however, and you may experience the sting firsthand.
Velvet ants -- scientifically known as Dasymutilla occidentalis -- can be found across the United States and into southern Canada. They are most visible in the summertime, when lone females can be spotted wandering through lawns or on patios or driveways. Velvet ants can be distinguished from ants by their antennae, which are straight rather than bent, and their lack of narrowing at the waist. Females are wingless and flightless, while the stingless male velvet ants exhibit two pairs of see-through black wings. Unlike a honey bee, the female keeps her stinger after she stings; as a result, she can sting repeatedly. Velvet ants chirp, squeak and even squeal when disturbed.
Adult velvet ants live on nectar, but wage savage battles with the cicada killer wasp in order to reproduce. Cicada killer wasps survive by killing cicadas, dragging them back to their underground burrows, and laying eggs on them; the cicada carcasses serve as food sources. When the eggs hatch, the larvae of the cicada killer wasp feed on the cicada carcass. Velvet ants, in turn, enter the burrows of cicada killer wasps and lay eggs on the cocoons of the wasp's young; when the velvet ant larvae hatch, they devour the developing larvae of the cicada killer wasps. The grub-like larvae then use the shell of the cicada wasp killer to house their own cocoons. If the velvet ant makes the mistake of entering the burrow when a parent is present, it is usually overpowered and killed.
For people who are not allergic, the sting of a velvet ant is no more dangerous than the sting of any other wasp or bee, and can be treated the same way. MayoClinic.com advises treating bee stings by washing the area with soap and water, and applying cold compresses to reduce swelling. An antihistamine such as diphenhydramine, also known as Benadryl, also can help reduce swelling. In rare cases, a severe allergic reaction called anaphylactic shock can occur. Symptoms include hives on places other than where you were stung, difficulty breathing, swelling of the throat and tongue, dizziness or fainting. This can be a life-threatening emergency; call 911 immediately.
Velvet ants are loners that don't live in colonies or build nests; as a result, their numbers usually are few. They cause no damage to crops, houses or gardens. The Ask the Exterminator website notes that there are no chemical controls that target velvet ants. You may be able to discourage velvet ants by eliminating bare, sandy areas in your lawn, which attract the wasps on which velvet ants feed.