Fire ants adept at both stinging and surviving

Give the lowly fire ant credit: Not only does it possess one heck of a sting, it’s apparently a pretty good engineer, too.

Researchers at Georgia Institute of Technology, studying these pesky members of the family Formicidae, have found that fire ants are not only able to make rafts out of their own bodies to stay afloat in water, but that their rafts are extraordinarily well-built.

“The towers, bridges and boats that ants build are remarkable in part because they’re strong and light and they adapt to their surroundings – and because ants serve as both the construction workers and the raw materials,” according to the Los Angeles Times. “Ants use their bodies like the beams in a building; instead of screwing or nailing those beams together, they reach out and touch each other.”

“It’s like their bodies are covered in Velcro,” said study co-author David Hu, a mechanical engineer at Georgia Tech.

Using a miniature CT scanner, the researchers were able to analyze the rafts and found that 99 percent of the fire ants had all their legs connected to neighbors.

Scientists were able to learn this by putting 110 live ants in a beaker, swirling it around so the ants would start to form tiny rafts, flash-freezing them in place and then examining them under the scanner, according to the Times. They did this four times in all, using a total of 440 ants with a total of 2,640 legs (each ant has six limbs).

The connectivity produces enough strength to keep rafts intact despite the pull of rough currents, according to Georgia Tech research published in a paper in the Journal of Experimental Biology.

“Now we can see how every brick is connected,” Hu said. “It’s kind of like looking inside a warehouse and seeing the scaffolding and I-beams.”

On average, each ant in a raft connects to nearly five neighbors. Ants have six legs, but using their claws, adhesive pads and mandibles, each ant averages nearly 14 connections, with some large enough to handle more than 20 connections, the researchers found.

Hu and his team also noticed that the insects used their legs to extend the distances between their neighbors.

“Increasing the distance keeps the raft porous and buoyant, allowing the structure to stay afloat and bounce back to the surface when strong river currents submerge it,” said Nathan Mlot, a Georgia Tech graduate student involved in the research.

The researchers found that smaller ants tend to fill in the spaces around large ants.

“This keeps water from seeping in and prevents weak spots in the raft,” according to the Georgia Tech. “The insects, large and small, arrange perpendicularly rather than parallel. This adds to the adaptability of the raft, allowing it to expand and contract based on the conditions. The same is true when ants build towers and bridges for safety and survivability.”

This study comes on the heels of recent research that found that fire ants took advantage of the buoyancy of the brood (containing developing larvae and pupae) by placing it at the base of rafts to boost the overall survival rates and to minimize ant injury or death.

(Top: Fire ant raft displaying buoyancy properties that enable it to withstand rough currents. Using a stick, the ants can be pushed down, but will bounce back to the surface, thanks to the make-up of the raft. Photo credit: Tim Nowack.)