The (little) big bug battle

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iol scitech feb 14 crazy ants

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While an individual ant hunting for something to eat wanders in a random path, their collective behaviour turns chaos into order.

Washington - You may have heard of “Dracula vs. Frankenstein,” “Freddy vs. Jason” or even “King Kong vs. Godzilla.” But you can add to this list of epic battles: tawny crazy ants versus fire ants.

Only this time, it's not film fantasy.

These two kinds of ants are natives of South America that have shown up as unwanted imports in the United States and are fighting each other over food and nesting sites across the southeastern United States.

The crazy ants - the relative newcomers in this confrontation - are whipping the fire ants, and scientists at the University of Texas have figured out why.

In a study published in the journal Science on Thursday, they report that crazy ants boast a unique way of neutralising the potent venom of the fire ants. They smear their own brand of venom on their bodies after being hit with venom by a fire ant foe, successfully detoxifying themselves.

This chemical defence system represents a game-changer in the arms race between these two ant species.

“This is likely primarily the reason why this ant is displacing fire ants in areas it's invading,” Ed LeBrun, an expert in invasive species at the University of Texas, said in a telephone interview.

Both species are natives of northern Argentina, Paraguay and southern Brazil, and the scientists believe the crazy ants developed their defence there long ago.

The red-and-black fire ants are named for the painful stings that feel like fire on humans and other animals. They arrived in the United States in Mobile, Alabama, in the 1930s, most likely after hitching a ride in ship ballast.

They then spread throughout southeastern United States.

The tawny crazy ants, known for their butterscotch colour and the erratic way they walk when foraging for food, arrived in 2002. They were first documented near the Houston shipping channel and at about the same time in Florida.

Fire ants dominate most other types of ants by splattering them with powerful, typically fatal venom that is even more toxic than DDT. But when a crazy ant gets hit, it resorts to its detoxification procedure. It stands on its hind and middle legs, oozes formic acid from a gland at the tip of its abdomen, smears it on its body and neutralises the fire ant venom.

To gauge how well the formic acid worked, the scientists used nail polish to seal the glands of the crazy ants and put them in vials with fire ants. Without their chemical defence, 48 percent of the crazy ants hit with fire ant venom died. When crazy ants had unsealed glands, 98 percent survived the fight.

“I wanted to understand why these tawny crazy ants were able to displace fire ants, because fire ants are very serious competitors and very difficult to defeat. Fire ants are pretty nasty customers,” LeBrun said.

LeBrun added that unless something changes, crazy ants will displace fire ants in much of the southeastern United States and become the new ecologically dominant invasive ant species.

The researchers reported last year that in places where crazy ants arrive, creatures such as insects, spiders, centipedes and crustaceans decline, which could affect ecosystems by reducing food sources for other animals. The ants also nest in people's houses and harm electrical equipment. - Reuters

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