If you’re a nature lover, you might be familiar with the term “warning coloration.”
It’s also known, more technically, as “aposematic coloration.” Both terms refer to organisms that have evolved to sport bright, contrasting colors as a kind of danger signal to the world at large.
Typically, these creatures are venomous, poisonous or foul-tasting.
In the realm of arthropods, aposematic coloration is commonly associated with stinging insects from the order Hymenoptera which includes wasps and ants. Perhaps the best-known example is the yellow jacket, which has bold yellow and black bands across its abdomen.
Another aposematically colored member of the Hymenoptera order is an insect commonly known as the velvet ant.
These insects aren’t ants! They’re wasps. But the females are wingless and their general body structure is similar to an ant’s. Their color pattern – black and bright orange-red – adds to the impression.
Velvet ants are members of the family Mutillidae, and Florida is home to about 50 species in seven genera.
One of the species that Florida residents are most likely to encounter is Dasymutilla occidentalis occidentalis.
It’s a solitary creature, with females reaching a maximum length of about 1 inch. Florida residents are most likely to see them crawling swiftly across the ground in sandy upland areas, including yards, parks and pastures. On a bright summer day they can be amazingly easy to spot because their bodies are covered with coarse hairs called setae, which reflect sunlight effectively.
That’s a good thing, because you do not want to overlook one of the females. They can sting, whereas the males cannot. (The males also have wings, which the females lack.)
Velvet ants are not especially aggressive, but may sting if threatened (usually during rough handling or if they’re stepped on.) Tests indicate that their venom is considerably less toxic to mice than the venom of the European honey bee. You can read a detailed assessment of insect venom toxicity.
That said, velvet ants have a fearsome reputation for toxicity. Long-time Florida residents may recall another nickname for them – “cow killers.” It’s commonly believed that velvet ant venom is so powerful that a few stings will literally end the life of a cow or bull.
However, there doesn’t appear to be any scientific evidence to support that belief. The BugWeek Web Team has searched for published studies indicating that velvet ant venom is especially toxic to cattle, and we’ve come up empty-handed.
But we did come across one proposed explanation of the name “cow killer” that seems plausible.
We can’t attest to its accuracy, but here it is…
Cows have cloven hooves, meaning that there’s a notch in the front of the hoof, splitting it into two distinct segments. That much is beyond dispute.
Well, according to one online commenter, the tissue in that notch is soft enough for a female velvet ant to penetrate with her stinger. So, if a cow is unfortunate enough to accidentally step on a velvet ant and receive a sting in that spot, the cow will quite possibly react to the pain by charging across the pasture at top speed.
Though the sting itself is survivable, if the cow happens to crash into fencing or step into a gopher tortoise hole and break a leg, the rancher may have to euthanize the cow. Supposedly, this was a fairly frequent occurrence in the rural South, and occasionally the velvet ant would be found afterward, still lodged in the hoof.
Thus, ranchers supposedly began calling velvet ants “cow killers” because that was the end result of some sting incidents. Other, non-ranching folks who heard the term but not the story behind the origin jumped to the erroneous conclusion that the velvet ant’s venom was much more potent than it truly is.
The BugWeek Web Team has no ranching experience, so we can’t attest to the truth of that explanation. But it sounds plausible, and hopefully it helps you realize that these beautiful creatures are not a menace, but a natural wonder we can all enjoy – from a safe distance, of course.
You can read more about velvet ants in this “Featured Creatures” document from the UF/IFAS Department of Entomology and Nematology.