The English had the longbow. The Spanish had steel. Tawny crazy ants have their own formidable weapon—a protective acid sheath—that protects them against fire ant enemies. The revelation comes from a new study published this week.
Named for their butterscotch color and erratic movements, tawny crazy ants are the newest insect invaders sprawling throughout Texas and the Gulf states, unseating the reigning imported fire ants that have infested the region.
Teeming out of electrical outlets and short-circuiting electronics, the tiny reddish-brown crazy ants have been making headlines as their numbers climb in the southeastern U.S. In some locales they can be so tightly packed together they are initially mistaken for dirt. Then they move.
As their population swells, the ants, formally known as Nylanderia fulva (but also sometimes called Rasberry crazy ants in honor of the Texas exterminator that discovered them), are harming the environment—not to mention people’s homes and electronics.
Now we have a new clue as to why they are able to prevail over the previously dominant fire ants: Crazy ants produce chemicals they then rub on themselves as an antidote to fire ant venom. And the acidic substance exuded from where a stinger would be located on other ant species also doubles as a chemical weapon they spray at foes, allowing the crazy ants to defeat competitors that would otherwise help keep them in check.
The discovery stemmed from some initial observations of odd, and sometimes disturbing, ant behavior. Since these ants, native to northern Argentina and southern Brazil, first started showing up in Texas in 2002 it has been unclear why they were able to flourish. But it is undeniable that they do.
When fire ants and crazy ants show up in roughly equal numbers and go for the same tasty cricket treat, new work reveals that the crazy ants typically win some 93 percent of the time. Moreover, many crazy ant colonies have been spotted inside fire ant mounds that still are home to some of their previous tenants, raising the alarm among bug experts that crazy ants can apparently snatch active nests from their cousins with ease.
Edward LeBrun, a researcher at the University of Texas at Austin, and his team published these and other findings February 13 in Science. One of the team’s astute observations that fueled their research into the ants’ chemical arsenal: crazy ants that had been involved in fire ant skirmishes typically engage in a very particular behavior sequence.
After a run-in with a fire ant a crazy ant would stand on its hind and middle legs, fully curl up its body to touch its glandular opening at the tip of its abdomen to its mandibles, and then seemingly groom itself vigorously, rubbing a secretion along itself to apparently detoxify the venom. LeBrun’s team decided to dive further into what was happening.
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