Crazy ants and fire ants have been competing for survival for centuries. Both species are common in the United States, and now it seems tawny crazy ants have adopted a new means of chemical warfare in the battle for dominance.

When these two species meet, the scene can look like a miniature version of a classic war movie. Both sides in the battle employ a wide range of weapons to destroy the others. Thousands of insects die on each side during the conflict.

Fire ants first arrived in the U.S. from South America during the 1960's. Most insects, and even humans, shy away from contact with the species. Bites from one of these tiny insects deliver a powerful toxin. In humans, the effect can produce painful swelling, pus-filled blisters and scabs that can last up to a week. Many people are also allergic to fire ants, and develop a rapid heart rate and have trouble breathing when they encounter the venom.

Tawny crazy ants (or Nylanderia fulva) are relatively newcomers to the U.S., first appearing in 2002. They are smaller than fire ants, but march into battle against the other species without hesitation. When fire ants sting a crazy ant, the victim will retreat from the battle. Crazy ants then use formic acid within their own powerful venom to act as a healing salve for the fire ant toxin. The acidic mixture is secreted from their abdomens, and spread over their bodies using tarsus, the closest features ants have to hands.

When the tiny creature is healed, "they'll run right back in to fight and take on another fire ant," Edward LeBrun, an entomologist at the University of Texas at Austin, told Popular Mechanics. This strategy is working, as tawny ants are now winning the race for survival in the American southwest. "Other ant species typically avoid fire ants. Fire ant venom is so toxic that it's not something other ants will confront. But these crazy ants will just charge on into the fray with what seems like wild, willful abandon," LeBrun said.

LeBrun and his team, whose study has been published in the journal Science, introduced tawny ants to other aggressive ant species, in "antagonistic interactions." When these were carried out, the tiny creatures acted the same as they did when battling fire ants. The tawny ants attempted to heal themselves with their own venom. However, the effect of the antidote on toxins from other species may be minimal. This could suggest the adaptation evolved just for healing from battle against fire ants.

Both species of ant prefer warmer climates, and do not live where the ground freezes over. Therefore, each type of ant is likely to remain in southern parts of the United States. Where both species are found in North America in large numbers, tawny crazy ants are winning the war for survival.

The battle continues worldwide between fire ants and crazy ants. In North America at least, this new adaptation appears to give the tawny crazy ant the upper... tarsus.