FIRE ANTS: PAINFUL AS THE NAME SUGGESTS
Their name screams it all: FIRE ANTS. If you don’t know anything about them, millions of people in the southern U.S. do, having learned the hard way. Being mass-stung by an angry horde of fire ants is an unforgettably painful experience.
To Eldridge Adams, Assistant Professor at the University of Connecticut’s Department of Ecology and Evolutionary Biology, the multi-stings of fire ants are as familiar as handshakes. He’s been stung hundreds of times, since fire ants are major subjects in his field studies.
Native to South America, fire ants were ferried unwittingly to the U.S. on a cargo ship from Brazil. A breeding colony jumped ship in Mobile, Alabama, around 1920. Once established, the ants adapted exceptionally well to the southern U.S., spreading like the plague they are into a belt now reaching from Virginia to southern California. These imported fire ants are a single species, Solenopsis invicta, though there are several other species of fire ant in nature. S. invicta is now the most seriously pestiferous ant species in the U.S.
Dr. Adams’s two major areas of study are the population ecology and behavior of social insects. Originally from Los Angeles, as an undergraduate at Harvard from 1975-1979, he studied ants with entomologist Bert Holldobler.
Why study fire ants? “Fire ants are excellent subjects for studies on social cooperation and competition and the effects of behavior on population dynamics” he says. They’re also convenient, because, Adams explains, fire ant colonies grow quickly and their mosaics of abutting territories allow abundant opportunities for studying interractions among colonies. Since they’re a pest species, fire ants have been studied more than any other ant species, so a much is already known about them.
Adams keeps about a hundred thriving colonies of fire ants on hand at Torrey Life Sciences at Uconn, safely out of the way in a double-doored room.
Aggressive, omnivorous, and producing high population densities, fire ants feed on insects and related creatures, dead vertebrate animals, and seeds. They build their underground castles in fields, roadsides, and lawns. Newly founded colonies may have only one queen or several queens with their broods all working together.
Currently, with a three-year grant from the National Science Foundation, Adams is researching how adjacent fire ant colonies struggle for control of space and how colony sizes change through time. “I’m studying border wars between neighboring colonies,” he explains, “and how neighboring colonies of different sizes divide up the space that’s available to them. I’m developing a model that allows prediction of where boundaries will be established by territorial animals or colonies. The model assumes that territorial residents push aggressively at neighbors along the borders. I’ll be using field data and experiments to measure how hard neighbors will push and how that shapes their territories. I’m seeking to understand how competing neighbors establish a boundary. This is the case for fire ants and many other territorial animals, including birds. The animals fight to establish a boundary that is then respected by the bordering neighbors.”
Adams’s studies have added significantly to our knowledge of fire ant behavior and that of communal animals in general. He’s shown that colonies founded by multiple queens are more likely to win brood raids (they have larger armies of workers), are less likely to see their queens displaced by invading queens and are less likely to be overrun by raiding workers from mature colonies, than are young single-queen colonies.
Adams has shown that the workers in a multiple-queen colony show preferences for a particular queen and eventually kill the extra queens. He’s demonstrated that the populations of mature colonies are regulated by competition among colonies for foraging space. Adams has produced a mathematical model of territory size and shape, based on his research of fire ants, that predicts much of what researchers see in field studies.
Presently, Adams is experimentally testing this prediction model and extending it. “What I want to be able to do is to see how changes in the environment-especially food supplies-affect the behavior of colonies and then in turn how that drives their population dynamics.”
Studying fire ant behavior has wider applications, says Adams.
“Many of the specific things we’re studying in fire ants are instances of broader themes that ecologists study. Behavioral ecologists are very interested in the mix of cooperation and competition that occurs within social groups. What we find happening in fire ant populations in one sense tells us something very specific about what a particular species does, but part of the point of this work is that this is a species within which it’s very easy to do experimental work on this mix of cooperation and competition, and to see how it affects the fates of individuals and groups. This information can be used to test theories that have broader applicability to social animals.”