Engines of Our Ingenuity

No. 457:
INVICTA FIRE ANT

by John H. Lienhard

Click here for audio of Episode 457.

Today, we learn a hard lesson about compensation in nature. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

It was 1982. I was looking at an empty house with house-hunting friends, moving into town. We stood in the yard to look at the roof. Suddenly pain bathed my lower leg. I looked down. It was crawling with ants. By the time I'd run into the house and stripped off my shoes, socks, and pants, they'd stung me in 40 places. I was out for the day. My leg took weeks to heal.

That was my first meeting with an insect called Invicta, -- Latin for invincible. He's better known as the fire ant. First he bites into you to form a grip. The bite's harmless; but then he stings you. He injects a mixture of venom and bacteria. It leaves a nasty, painful, and slow-healing little wound.

We've spent millions for a chemical assault on fire ants. The chemicals have done more to clear out the fire ant's natural insect enemies. They've killed birds. They've left carcinogens in human tissue. And the fire ants have prospered.

The ants that stung me came out of a single queen mound. Unpleasant as that was, it was only a bother -- not a real threat to my life. Meanwhile, the species has mutated under attack. Now Invicta has learned to create mounds with many queens.

The mutant creates vast burrows with millions of workers. The females are the gatherers and they're omnivorous. They go after other insects, crops, even highway expansion joints. Veterinarians at Texas A & M have treated dozens of young deer for fire ant bites. Electric fields draw the ants. They've knocked out relays, traffic lights -- even airplane altimeters.

Entomologists are working on two lines of battle. One is chemical. They've given up on insecticides. Now they look for chemicals that miscue the mating process or sterilize the queens.

The other attack is not chemical at all. It's sociological. We're looking around for the fire ant's natural enemies. Invicta mounds in Brazil offer clues. Many are shared by other insects. Maybe some of those bugs keep Invicta in check.

One insect is a sure enemy of the new fire ants. His identity is the crowning irony in the whole business. It turns out that the old single-queen colonies are vicious enemies of the multiple-queen mounds. In the end, we might find ourselves using the old ants to fight the new ones.

If it's any consolation, the old single-queen fire ant isn't entirely bad to have around. He's a tough natural enemy of other pests -- like corn worms and boll weevils. And he'll really control the flea population in your back yard.

I'm John Lienhard at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


Lewis, P.H., Mighty Fire Ants March Out of the South. The New York Times, Science Times, Tuesday, July 24, 1990, pp. B5 & B8.


The Engines of Our Ingenuity is Copyright © 1988-1997 by John H. Lienhard.

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