February 14, 2014
Fire Ants Being Displaced By Venom-Neutralizing Crazy Ants
[ Watch the Video: Crazy Ants Attack Fire Ants ]
April Flowers for redOrbit.com - Your Universe OnlineIn areas across the southeastern United States, invasive "crazy ants" are rapidly displacing fire ants by secreting a compound that neutralizes the fire ant's venom, according to a new study from The University of Texas at Austin. The crazy ant is the first known example of an insect with the ability to detoxify another insect's venom.
The latest in a wave of ant invasions from the southern hemisphere, the crazy ant invasion will likely have similar dramatic effects on the region's ecosystems.
Fire ants are known for their painful stings, both on humans and animals. They dominate most other ant species by dabbing them with powerful, usually fatal venom. On a per weight basis, the venom—which is a topical insecticide—is two to three times as toxic as DDT.
When a fire ant smears a crazy ant with the venom, however, the crazy ant immediately starts a detoxification procedure. The study, published in Science Express, describes how the exposed ant secrets formic acid from a specialized gland at the tip of its abdomen, transfers it to its mouth and then smears it on its body.
Exposed crazy ants that were allowed to detoxify themselves during laboratory experiments had a 98 percent survival rate. The crazy ants are nearly invincible in battles with fire ants over food resources and nesting sites because of this chemical counter-weapon.
"As this plays out, unless something new and different happens, crazy ants are going to displace fire ants from much of the southeastern U.S. and become the new ecologically dominant invasive ant species," said Ed LeBrun, a research associate with the Texas invasive species research program at the Brackenridge Field Laboratory in UT Austin's College of Natural Sciences.
The researchers reported last year that when crazy ants take hold in a region, the numbers and types of arthropods—insects, spiders, centipedes and crustaceans — decrease. This decrease is likely to have ripple effects on ecosystems by reducing food sources for birds, reptiles and other animals.
In a battle for food between red fire ants and crazy ants along the boundary line between their two populations at a Texas field site, LeBrun observed a strange behavior. The fire ants had discovered a dead cricket and were guarding it with large numbers. Other ant species usually steer clear when fire ants amass because of the venom.
"The crazy ants charged into the fire ants, spraying venom," said LeBrun. "When the crazy ants were dabbed with fire ant venom, they would go off and do this odd behavior where they would curl up their gaster [an ant's modified abdomen] and touch their mouths."
This led LeBrun to suspect that the crazy ants were detoxifying the fire ant venom. Experiments conducted at the Brackenridge Field Laboratory in Austin allowed his team to identify the detoxification agent and measure its effectiveness.
The research team sealed the glands of crazy ants with nail polish to test the effectiveness of the formic acid. These ants were placed in vials with red fire ants. Approximately half of these crazy ants, who were without the ability to detoxify themselves, died from the fire ant venom. On the other hand, a control group of crazy ants, with unsealed glands, had a 98 percent survival rate.
Both species, crazy ants and red fire ants, are native to northern Argentina and southern Brazil. In this region, their ranges have overlapped for a very long time, suggesting that although this detoxification behavior is newly discovered, it developed as part of an ancient evolutionary arms race.
Human intervention, according to LeBrun, is the only thing stopping the relentless march of the crazy ants—other than natural factors such as arid soils or severe freezes, that will be too harsh for them to survive. The range of the crazy ants, like the red fire ants before them, will ultimately be determined by geology and climate.
The crazy ant invasion contains one bright spot for humans, crazy ant colonies spread very slowly. Unlike fire ants, they only spread about 600 feet per year unless transported by people in potted plants and recreational vehicles. The researchers suggest not buying plants with ants nesting in them, and to check for stowaways when they move homes or travel long distances.
"If you have an RV, inspect the campgrounds you visit before parking for the night," said LeBrun. "If you live in infested areas, don't store food in your vehicles and consider treating your camper with insecticides several days before a trip. Consult with a pest control professional as to the best products to use. Not storing food in any vehicle parked in an infested area is also a good idea."