Crazy ants dominate fire ants by neutralizing their venom

"The crazy ants charged into the fire ants, spraying venom," said LeBrun. "When the crazy ants were dabbed with fire ant venom, they would go off and do this odd behavior where they would curl up their gaster [an ant's modified abdomen] and touch their mouths."

It was then that LeBrun first suspected the ants were somehow detoxifying the fire ant venom. Experiments back at the Brackenridge Field Laboratory in Austin helped him and his colleagues identify the detoxification agent and measure its effectiveness.

To test the effectiveness of the formic acid, researchers sealed the glands of crazy ants with nail polish and put them in vials with red fire ants. Without the ability to apply the detoxifying compound to themselves, about half of the crazy ants dabbed with fire ant venom died. Among a control group of crazy ants with unsealed glands, on the other hand, 98 percent survived.

Crazy ants and red fire ants are both native to northern Argentina and southern Brazil, where their ranges have overlapped for a very long time. The researchers suggest this newly discovered detoxification behavior is the result of an ancient evolutionary arms race.

It's still not clear how formic acid renders imported fire ant venom nontoxic. One possibility is that it prevents the venom from penetrating the outer layers of a crazy ant's exoskeleton.

Apart from human intervention, said LeBrun, the only thing stopping the relentless march of the crazy ants will be natural factors, such as arid soils or severe freezes, that will be too harsh for them to survive. Like the fire ants before them, their range will ultimately be determined by geology and climate.

There is one bright spot for humans. Unlike fire ants, colonies of crazy ants spread very slowly — about 600 feet per year. The only way they can spread long distances is when transported by people in potted plants and recreational vehicles. LeBrun suggested that people not buy plants if they see ants nesting in the pots and that if they live in areas already invaded by crazy ants, they check for stowaways when they move homes or travel long distance.

"If you have an RV, inspect the campgrounds you visit before parking for the night," said LeBrun. "If you live in infested areas, don't store food in your vehicles and consider treating your camper with insecticides several days before a trip. Consult with a pest control professional as to the best products to use. Not storing food in any vehicle parked in an infested area is also a good idea."

In this video, a fire ant dabs venom on an attacking crazy ant. The crazy ant coats itself with formic acid to neutralize the venom, a discovery made by University of Texas at Austin researchers. This is the first known example of an insect with the ability to detoxify another insect's venom, and it is likely helping the crazy ant beat out fire ants where the two species overlap.

(Photo Credit: Ed LeBrun)

Crazy ants (on the right) coat themselves with formic acid to neutralize the venom of the fire ant (at left).

(Photo Credit: Lawrence Gilbert, University of Texas-Austin.)

Source: University of Texas at Austin