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Fire ants form “rafts” in flooding

From Southeast Farm Press

Amid all this heavy spring rainfall, fish pond owners not only should be mindful of flooding but also of the great balls of fire that often accompany flooded ponds.

While these fireballs are no harbinger of doom, they can bring painful stings and, based on some evidence, possibly fish kills.

At closer inspection, these balls are actually large masses of imported fire ants.

Nature has equipped these fire ants with an unusual skill. During periods of severe flooding, these ants, fleeing washed out colonies, form themselves into huge balls — rafts, as insect experts describe them — in an attempt an escape to drier ground.

These rafts are held together by a collective effort, with all the worker ants joining hands, or tarsi, as insect hands are called, according to an online eXtension publication by Linda-Hooper Bui, a fire-ant expert and associate professor of entomology at Louisiana State University.

The highly adaptive workers constantly move around these rafts, assuring that individual ants are not submerged in water for long.

The ants carry the eggs and tiniest larvae in their mouths. Older larvae and pupae are kept at the bottom of the raft, helping the structure stay afloat.

Winged males aren’t so lucky: They are the first to be jettisoned.

(To see a YouTube video of a fire ant bridge, see

http://www.youtube.com/watch?v=r04kAnzgjR4. A video of a fire ant raft is at http://www.youtube.com/watch?v=7BYSgSaqOo4).

For his part, Russell Wright, an Alabama Cooperative Extension System fisheries specialist and Auburn University associate professor in the Department of Fisheries and Allied Aquaculture, expresses amazement at the adaptive traits these ants have demonstrated around fish ponds.

“They seem to be very well adapted to fluctuating water levels in soils,” Wright says. “We even noticed that the ants will use the dense vegetation to move right across the surface of some ponds to forage for insects.”

In cases of pond flooding, Wright says the ant rafts will float out into the pond in search of dry land, with the ants crawling onto protruding sticks and other surface material in search of safe havens. Some of them eventually make it back to shore.

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