Secrets of a Supercolony
Watch out, European ants! A huge colony of Argentine ants is invading your turf.
About 1920, a small colony of Argentine ants left their home in South America. They most likely hitched a ride on a ship. Their journey took them thousands of miles away, to Europe. Scientists believe there were as few as 10 ants in the colony.
Today, that colony of ants not only still exists in Europe, but it has grown. It is now a billion-member supercolony that stretches 5,760 kilometers (3,600 miles), from the coast of Italy to northwest Spain (see map on page 13). That's even longer than the United States is wide!
This supercolony is made up of millions of nests. Normally, ants from different nests fight, but these ants get along. So what's the secret to this supercolony's success? These ants are all related. They don't fight because they recognize one another as family.
How do ants recognize their kin? "Through their sense of smell," explains Neil Tsutsui from the University of California, Davis.
Since members of a colony are related, they share many genes-' including those that determine their scent. All ants in a colony have the same smell. This allows them to tell the difference between colony members and outsiders. all outsiders, even those that live in nearby nests, smell different. They get attacked.
All in the Family
The Argentine ants expand their supercolony by moving to other nests. They either take over an enemy's nest or start a new one. Since these ants still smell like relatives from their old nest-and not like outsiders-they don't get attacked.
Argentine ants can expand to other nests because they have many queens. Every ant nest needs a queen to lay eggs. Most ant colonies have only one queen. But Argentine ants are different. They have up to eight queens for every thousand worker ants and drones. "This allows some of the queens, workers, and drones to leave the old nest and start a new one nearby," says Laurent Keller of the University of Lausanne in Switzerland. This is called budding.
The members of the supercolony may get along with one another, but they're nothing but trouble to the ecosystem around them. The supercolony works like a huge h invading army against other ants and insects. Experiments have shown Argentines defeating ants six times their size. They even scare away fierce, biting bugs like wasps.
"The Argentine ants have killed off 90 percent of other types of ants living near them," says Keller. They also eat many insects. "This affects birds by decreasing the amount of food available to them."
With all the damage the super-colony has caused, scientists are hoping it will one day be stopped. But how? Researchers have found a second, smaller supercolony in Spain. If the two different supercolonies meet, they'll fight and possibly wipe each other out. Parasites or disease may also destroy the ants.
Still, Tsutsui doesn't want to wait around. He'd like to use smell against the ants. he thinks chemicals from one colony could be collected and sprayed onto the other. That would trick the ants into fighting members of their own colony. But before Tsutsui's plan can be tried, researchers must learn more about how ants identify one another.
Let's hope scientists come up with an answer soon. Argentine ants aren't a problem just in Europe. The tiny critters have invaded every continent on earth, except Antarctica.
In fact, if you live in Texas or southern California, one maybe marching toward your sugar bowl right now!