Q: I was out watering my cows and stepped into a big fire ant mound. Thankfully, I’m not very allergic to their bites but the experience brought up the question of repellents. Why aren’t mosquito repellents effective on fire ants?
A: Because fire ants don’t use carbon dioxide to find their prey! Mosquitoes, like Aedes aegypti, think of you only as a hearty meal. Their antennae pick up wafting molecules of perfume, carbon dioxide and other scents to locate their victim.
Dr. Beverly Sparks, Extension service entomologist says that mosquito repellents work by confusing the insects’ carbon dioxide receptors. Botanical chemicals (citronella, lemon oil, etc.) accomplish the feat for a short time but the chemical known as DEET (Off!, Cutters, etc) seems most effective for most people. The June, 2002 issue of Consumer Reports magazine had an excellent article comparing chemical and botanical repellents.
To a fire ant you are not food, you’re a menace. Unlike mosquitoes, fire ants have a social system that utilizes a mass response against threats. When you stepped on them, the ants came boiling out of their mound looking for the perpetrator. As you probably observed, neither flailing palms nor stomping boots could keep them from their appointed task: stinging their adversary.
Only caustic chemicals or fast-acting poisons have a chance of repelling a fire ant. In this case, I think the solution would be worse than the problem.
On a related note, since you work with cows, you, more than most, need to use a mosquito repellent. Mosquitoes are attracted to the chemical octenol, which you would recognize immediately as the smell of cow breath. As my mother says, “If you lie down with dogs, you get up with fleas.” In your case, “If you hang out with cows, you get bit by Aedes!”