Invasive 'crazy ants' are nastier and far tougher than we imagined

Illustration for article titled Invasive crazy ants are nastier and far tougher than we imagined

There's an arms race going on right now between two species of invading ants, the tawny crazy ant and the fire ant. These arch-rivals are currently warring for dominance in the southern U.S., but it now appears the crazies are going to win — the result of a remarkable chemical defensive measure.

Red imported fire ants (Solenopsis invicta) first came to North America in the 1920s. They were followed by their South American cousin and rival, the tawny crazy ant (Nylanderia fulva) in the 1980s. These ants competed for resources alongside each other while they were still in South America, but now, as invasive species, they're duking it out in various regions of the southern United States, including Texas, Mississippi, Florida, and Louisiana.

Tawny crazy ants, as we're learning, are a total headache. As they make their way north at a rate of 600 feet a year, they're wreaking havoc on populations of insects, spiders, centipedes and crustaceans. This is likely to cause deleterious effects on various ecosystems. They can't be stopped with conventional pesticide, they've been known to disable a huge industrial plant, and they frequently short out electrical equipment.


Now, the battle between the two species has resumed — but on a different continent. Remarkably, however, traces of their previous encounters, and they way each species evolved to deal with one another, remain.

Illustration for article titled Invasive crazy ants are nastier and far tougher than we imagined

In a new study authored by Edward LeBrun and colleagues from the Texas invasive species research program at the Brackenridge Field Laboratory in UT Austin's College of Natural Sciences, it was discovered that the tawny crazy ants employ a unique chemical defense that gives them a considerable advantage when duking it out with fire ants. Crazy ants can cover themselves with abdominal gland secretions that effectively detoxify their wounds after they've been stung by fire ants. It's the first known example of an insect that can detox another insect's venom.


And as many people know all too well, the sting from a fire ant is no joke. Fire ant venom is two to three times as toxic as DDT on a per weight basis.

After being stung, crazy ants stand-up on their hind and middle legs, curl their abdomens underneath their bodies, and begin covering themselves with a secreted formic acid. The researchers theorize that the acid is numbing the pain by removing enzymes in the fire ant's venom.


It's a detox protocol that allows upwards of 98% of crazy ants stung by fire ants to survive. Those who don't employ the detoxification behavior die at a rate of 48%. This makes the crazy ants nearly invincible, prompting LeBrun to write, "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."

Read the entire study at Science: "Chemical warfare in invasive ants: a novel detoxification interaction in a new environment ."


Images: Texas A&M University, Lawrence Gilbert/University of Texas-Austin.

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One of my favorite activities growing up in the desert was to head into the back yard (mostly dirt) with a shovel, take a scoop out of an anthill of big black ants and dump it onto a hill of fire ants. Then repeat the other direction. Epic ant battles.