Crazy ants can fight off fire ants, new study shows

Pearland exterminator Tom Rasberry lets "crazy ants" crawl on his arm in 2008. He first discovered the pesky insects around Pasadena in 2002. (AP Photo/David J. Phillip) Pearland exterminator Tom Rasberry lets "crazy ants" crawl on his arm in 2008. He first discovered the pesky insects around Pasadena in 2002. (AP Photo/David J. Phillip) Photo: David J. Phillip, STF Photo: David J. Phillip, STF Image 1 of / 69 Caption Close Crazy ants can fight off fire ants, new study shows 1 / 69 Back to Gallery

In the bug-eat-bug world of insect rivalry, the Rasberry crazy ant has a leg up on its bitter rival, the fierce-stinging fire ant. While the fire ants' poison is up to three times as toxic as DDT, the crazy ants - first spotted in Texas 12 years ago - pack a built-in antidote, a new University of Texas study reveals.

The discovery that crazy ants, which have infested sites along the Gulf Coast as far away as Florida, can neutralize their adversaries' toxin marks the first time such an ability has been documented among insects.

University of Texas ecologist Edward Lebrun, who this week published his findings in the journal Science Express, said he made the discovery while trying to determine why crazy ants were displacing fire ant colonies in Texas. Both ant species are native to South America and have caused damage to infrastructure and agriculture as they have moved across the southern United States.

"I put a dead cricket in an area between fire ant and crazy ant colonies and the fire ants immediately glommed onto the bait. I stopped counting at 400," he said Thursday. Usually nothing, not even vertebrates, will challenge fire ants in a feeding frenzy, he said.

As Lebrun watched, though, crazy ants launched an assault. "I thought they were making kamakazi runs," the researcher said. "But when they got smeared with fire ant toxin, a fate that should have been lethal, they went off to the side where they engaged in a very odd behavior."

The ants, he said, exuded a drop of formic acid - a potent poison in ant-to-ant warfare - sucked it into their mouths, ran their legs through their mouths, then applied the acid to their bodies.

After the acid detoxified the fire ant poison, the crazy ants charged back into battle.

In the laboratory, Lebrun sealed crazy ants' formic acid duct with fingernail polish, then placed them in a container with fire ants. When hit with fire ant venom, approximately half of the disabled crazy ants died.

All of the normal crazy ants in the study survived, he said.

The ability to neutralize fire ant poison gives crazy ants an advantage in competing for food. It is possible, the researcher said, that the acid prevents fire ant poison from penetrating the crazy ant exoskeleton.

Lebrun characterized his work as "basic science," noting it has no clear application in crazy ant control.

Pearland exterminator Tom Rasberry, who first discovered the insects in Pasadena in 2002, said several insecticides are effective in controlling the pests but are too costly to use over large areas.

Known for nesting in and disrupting electrical connections, the insects steadily marched through Southern states. Scientists say an untreated acre of grassland in infested areas might contain billions of the insects, which create multi-queen colonies in damp areas beneath rocks and debris.

For humans, crazy ants - which spray their toxin but do not sting - primarily are an annoyance. Rasberry, though, said they pose a potential menace to wildlife. "Beekeepers are going crazy over these ants," he said. "They decimate honeybees." They may also endanger other insects and animals by out-competing them for food, Rasberry said.

Fire ants, which deliver painful stings and typically attack en masse, long have been recognized as a threat to wildlife and humans. As much as $750 million is lost to farmers and ranchers annually as a result of ant attacks on livestock and crops.

Invasive fire ants are thought to have arrived in the United States in the 1930s aboard a freighter that docked in Mobile, Ala.