Fire Versus Crazy: Battle Of The Invasive Ants

Fire_ants02There’s a good chance you’ve heard of the red imported fire ant (above), a pest that’s found across the southern half of the U.S. and is now one of the world’s 100 worst invasive species. These aggressive ants, natives of South America, not only have a painful sting but also a penchant for attacking in swarms.

Less known is the Caribbean crazy ant, a more recent invader that’s been found in Florida and Texas (where it was once called the raspberry crazy ant). Unlike fire ants, Caribbean crazy ants — named for their erratic behavior — don’t have stingers and hardly bite. But infestations can be huge and incredibly hard to control. In one story from 2008, a woman describes how she kept killing and killing the ants that swarmed her house and within a week had filled a five-gallon bucket with dead ants.

News reports sometimes say that Caribbean crazy ants will attack and drive out fire ants, but there hasn’t been any scientific data that backs up the claims. So a trio of biologists from Rice and Texas A&M universities staged battles between nests of the two species. Their study appears in PLOS One.

The bad news is that, while there was no outright winner in the ant-on-ant combat, the crazy ants came off the worse of the two species; crazy ants were twice as likely to die as fire ants. It seems that the fire ants may be better equipped for a war, the scientists say. The fire ants are armed with stingers, which may be a more effective weapon than the crazy ants’ ability to spray formic acid. “It is possible that the ability to sting makes fire ants a more potent combatant than crazy ants,” the researchers write.

One odd thing that the scientists discovered is that crazy ants get more aggressive when they’re fed a low-carb diet. They even do better in battle and die less often when fighting fire ants. That’s different from most other ant species, which get more aggressive when given high-carbohydrate food. But what that means for which species wins out and spreads its misery farther, well, we’ll just have to wait and see.

Image courtesy of USDA/ARS via wikimedia

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