What to Know About Cow Killer Ants

Medically Reviewed by Poonam Sachdev on December 06, 2022
4 min read

Cow killer ants are not cow killers, nor are they ants. Instead, they’re wasps. These wasps are bright red, a warning for predators to stay away. Predators that don’t heed this warning are met with a nasty sting. While these stings are painful, they aren’t poisonous, and there’s no record of a cow killer ant killing a cow.

Cow killer ants (Dasymutilla occidentalis), also called red velvet ants and eastern velvet ants, are a species of velvet ant. Velvet ants are wasps, but named for their fuzzy, often wingless bodies that cause them to resemble large, furry ants.

Both wasps and ants are part of the order Hymenoptera, which also includes bees. Without wings, some wasps can look a lot like ants. They don’t have the typical node or nodes on the waist that ants have, but they have similarly shaped bodies. 

Cow killer ants are sexually dimorphic, meaning the males and females of the species have different characteristics. In the case of cow killer ants, the males and females look so different that many people don’t realize they’re the same species.

Female cow killer ants don’t have wings, so they’re most likely to be seen on the ground. They have black bodies covered in short, bright hairs that range in color from vibrant red to reddish-orange. They often have black hairs that make a stripe across the thorax, as well as black hairs on the legs and between the abdomen and thorax. 

Male cow killer ants have similar colors but slightly different patterns and they have dark brown or black wings. Cow killer ant size is also dependent on sex. Females are usually three-quarters of an inch long, while males can be larger.

Unlike other species in the order Hymenoptera, cow killer ants don’t live in colonies, hives, or nests. They’re solitary, meeting up with other wasps only to mate. Adult cow killer ants drink nectar from flowers.

Cow killer ants can’t kill cows, but they still have the potential to be dangerous. Both males and females have several tactics they use to keep themselves safe. Their bright red shade is an example of aposematic coloration, when an animal has bright colors to warn predators to stay away. Many animals, like the golden poison frog and the lion zebrafish, have aposematic coloration.

Other defensive tools that cow killer ants use include:

  • Their hard, strong exoskeleton
  • Releasing a smelly odor
  • Producing a chirping or squeaking sound by rubbing their legs together when they’re alarmed or disturbed 

Because female cow killer ants don’t have wings to fly away, they have an extra defense mechanism. Like other wasps, they can deliver a powerful sting. Their stinger is part of their ovipositor, or egg-laying organ, and they can deploy their stinger multiple times. 

On the sting pain index developed by entomologist Justin Schmidt, the cow killer ant lands a three out of four rating for pain. This is between the western honey bee (Apis mellifera), which scored a two and was described as “Burning, corrosive, but you can handle it. A flaming match head lands on your arm and is quenched with lye and then with sulphuric acid,” and the warrior wasp (Synoeca septentrionalis), which scored a four and was described as “Torture. You are chained in the flow of an active volcano. Why did I start this list?”

Despite the name “cow killer,” the sting can’t kill you. The venom is very painful, but it’s not toxic. Cow killer ants aren’t aggressive, either. They prefer to hide in leaves and mulch rather than attack.

While cow killer ants aren’t usually dangerous to humans, they can be very dangerous to other insects. Cow killer ants are parasitoid wasps. When a female is ready to lay her eggs, she’ll find the nest of another bee or wasp. She then punctures the host’s egg cocoon and lays one of her eggs inside. When the egg hatches, the cow killer ant larva feasts on the host's larvae, killing them.

Cow killer ants can be found throughout the U.S., but mainly on the eastern side of the country. They tend to prefer open areas, like clover fields, deserts, forest edges, and meadows. Females are often spotted on the ground, while you may notice a male cow killer ant while it’s drinking nectar from a flower or hovering above the ground.

You’re more likely to see cow killer ants and other species of velvet ants in warmer summer months. Unlike some other species of velvet ants, cow killer ants are not nocturnal. Instead, they’re active from sunrise to sunset.

Because cow killer ants don’t live in groups, there are rarely enough of them to cause an infestation. 

They prefer to stay outdoors and will rarely come inside. If you do come across one in your home, try to remove it very carefully. Because of their powerful sting, cow killer ants shouldn’t be removed with bare hands. Wear protective clothing and carefully trap the wasp so you can release it outside.

If you are concerned about cow killer ants entering your home, consider basic pest control practices like sealing up areas around doors and windows and closing up gaps and holes in your foundation.

You may encounter cow killer ants outdoors. Leave them alone, and let small children know not to touch them. Since cow killer ants aren’t aggressive, just stay away from their bright red coloring. Only female cow killer ants can sting, and they’ll only sting if they’re feeling exceptionally threatened. Avoiding them is the best way to prevent being stung.