Solenopsis xyloni

School of Ants collection
Literature record

Solenopsis xyloni

From Dr. Eleanor's Book of Common Ants

A.K.A.: Southern fire ants

Size: 0.1-0.18 inches

Where it lives: Sometimes bearing a resemblance to the nests of mini-red imported fire ants, Southern fire ants nest in mounds or flattened craters in open soil near moisture. They also can nest under carpets, in crawl spaces or under rocks.

What it eats: Southern fire ants have a healthy appetite for pretty much anything, including dead insects, sweets, greasy foods and sometimes seeds.

What’s the big deal?

Here is a story about a villain, a stinging sensation, and a possible hero. It is the story of the Southern fire ant, known to scientists as Solenopsis xyloni. Easily confused in appearance and behavior with the red imported fire ant (Solenopsis invicta, that notoriously bad guy from the southeast), Southern fire ants generally make their (much smaller) homes in small, loose dirt mounds in grassy openings or under rocks or boards more in the southwestern United States.

Our story begins with a villain and a few simple facts about the birds and the bees. Actually, just one fact: Birds and bees dread Southern fire ants.

As ground-dwelling predators, Southern fire ants can devastate ground-nesting birds like bobwhite quail. While a quail adult outsizes a Southern fire ant worker 160,000 fold, Southern fire ant nests can have upwards of 15,000 workers ( and who comb the ground with their pinchy mandibles and venomous stingers, swarming quail nests and devouring their much-smaller chicks. In fact, Southern fire ants rank up there with coyotes, skunks and badgers in the top four predators of bobwhite quail nestlings in Texas (Radar et al. 2007).

But their bad bird behavior doesn’t end with bobwhites. Southern fire ants also attack house sparrow chicks and baby endangered least terns (Hooper-Bui et al. 2004). Killing Southern fire ant nests increases least tern populations (Hooper et al. 1998) because Southern fire ants aren’t around to chomp away at their fuzzy little babies.

While the gruesome death of one of nature’s most squeezibly fluffy inventions (baby birds) may seem horrible enough, plants might argue they’ve got it even worse.

Let’s be a plant for a minute, maybe a happy little bush. Here we are in our field, and life is pretty sweet. The sun is shining on our leaves, and our flowers are just beginning to open and say hello to the world. We smell so good, enticing fat little bees to come bury their fuzzy heads deep within our petals for a drink of nectar. As they burrow in for a sip, they dust their heads with our pollen: an essential ingredient to our life cycle.

Hello, bees! We need these bees to visit us so we can do the one thing we need to do most in this big old world: Reproduce. Make seeds.

Normally, we love ants. They keep the number of pests squiggling around on us stable so we don’t get sick or depleted. But to us, these Southern fire ants are the WORST. First, they protect insects that can give us disease or suck us dry, harboring them against predators in exchange for a nectary treat the pests give them as a reward.

Lots of other ant species do the same thing, but not many are as good at it as Southern fire ants. Southern fire ants are such fierce protectors of their flocks of pestilence that they scare away anybody who comes near us (Morrison 2000), including pollinators like bees and butterflies (Ness 2006).

To make matters worse, these ladies rob nectar from our flowers (Kessler and Baldwin 2007). That is, instead of dusting their bodies with pollen and moving that pollen from flower to flower like bees do, these little jerks bypass our pollen and drink up our nectar.

That’s right: Not only do they make us lousy with all those pests, they also prevent us from making seeds (Ness 2006), our only task in life! When these ants get on us, we can’t get it on.

By now you might be thinking, these ants are just terrible. But I know one ant expert named Andrea who would disagree with you. “I love Southern fire ants,” she told me once. “They’re so cute and shy. They always try to run away from you. Besides, they’re native and they’re always getting pushed around by those other fire ants.”

This is the other side of Southern fire ants, the side that holds a valuable place in nature. They evolved with the natural environment across the southern United States, helping to regulate the balance of animals and plants in their natural home. Southern fire ants used to live all across the United States, but around the 1950s, red imported fire ants and their big, grumpy colonies began trouping across the southeast, stomping out many Southern fire ant nests in their way.

Have you ever met somebody with a bad reputation and expected to dislike them, only to find out that they were actually pretty nice? Like Andrea pointed out with her observation, this may be the case with the Southern fire ant; it’s possible that we just haven’t really met them yet.

With science, we only know what we have studied so far. We’ve studied Southern fire ants’ bird-eating, plant-hurting behavior, so that’s their reputation for now. But we have a lot left to learn about these insects.

How has the environment changed since red imported fire ants came and Southern fire ants left? How do Southern fire ants behave around other ant species? How often are we mistaking the deeds of red imported fire ants for those of Southern fire ants (Moore et al. 2008; Jacobson et al. 2006)? I’m sure you could come up with some good questions about southern fire ants yourself.

With science, we can build on and challenge what we know through exploration. We can form our own opinions based on information. Isn’t that wonderful? With science, you and I can each meet Southern fire ants, ask questions about them, and discover for ourselves more chapters in the Southern fire ant’s story.

Find out more about this species at Antweb and see more photos at Alex Wild's photography site.