Formica incerta

School of Ants collection
Literature record

Formica incerta

From Dr. Eleanor's Book of Common Ants

Species name: Formica pallidefulva, F. incerta, and Formica subscericea

A.K.A.: Field ants

Size: 0.2-0.4 inches

Where it lives: Field ants generally build their nests against trees, under rocks, or in logs.

What it eats: More buffet-style than picky eaters, field ants love sugar like aphid honeydew, soft-bodied insects like caterpillars, and seed husks.

What’s the big deal?

Formica ants, usually called “field ants,” are among the United States’ largest and most common ants. Found spanning the states in all directions, three species make the most common list: Formica pallidefulva and Formica incerta, both rusty-to-deep-red beauties, and Formica subscericea, black lovelies with stripes of sparse golden hairs across their rumps. Most field ants pass their days contentedly building their shallow, low-mound nests near rocks and trees, blissfully unaware of a dark underworld in their midst, a world of violence, slavery, mistaken identity, and poop shields.

About the size of one and a half pencil erasers, field ants’ long, dexterous legs extend from their thoraxes, and their large black eyes rest right behind their always-moving elbowed antennae. You can reliably tell a field ant if it’s a large ant, yellowish, reddish, black or red with a brown or black rump. Many people confuse field ants with carpenter ants, neither of which can hurt you. If you’d like to tell if you have a field ant, once you gently nab the ant in question and check out its thorax, the middle section of the ant where all of the legs attach. If its thorax consists of two lumps, you have a field ant. If it has one big hump, you’re holding a carpenter ant. What a way to impress your friends!

Field ants have large eyes because they usually move around during the day and rely on sight more than some other ant species. They use those big eyes to help them see landmarks as they scurry to and from food. Like many ant species, field ants love tending aphids and scale insects for their sugary emissions, but they also help disperse plants by toting seeds around the forest, snacking on the husks and discarding the rest. They enjoy wolfing down other insects whenever they get the chance.

Nice Outfit, Mr. Beetle

Because field ants prefer to eat soft-bodied insects like caterpillars and beetle larvae, their predatory tendencies help keep our trees happy. One of the United States’ most dangerous forest pests is the gypsy moth. Silk moths with huge appetites, gypsy moths have gobbled up more than 80 million acres of our northeastern forests in the last 40 years. When they scarf down all the leaves in the forest, trees die, causing millions of dollars’ worth of damage. Fortunately, field ants love those plump little leaf munchers. They help reduce the damage and spread of gypsy moths by eating every caterpillar they can find.

Sometimes their partiality for pudgy little insects lands field ants in unusual situations. Many baby beetles (often called grubs) fit the mold for a perfect field ant meal. Slow, soft and chubby, beetle grubs don’t stand a chance when hungry field ants stumble across them while foraging. To ward off potential beetle slayers, many beetle species, like tortoise beetles, found an inventive solution: poop shields.

Here’s how it works: Some plants in our forests and across our cities have certain “stop eating me!” chemicals in their leaves, called deterrents. When most insects bite into a leaf and smell the deterrents, they get as far away as possible. Not our resourceful beetle grubs. They eat as much of these stinky leaves as they can, pooping stinky leaf poop all over the place. Then they gather up the poop and stick it on their bodies, making a force field of stink that follows them wherever they go. Field ants catching a whiff of these otherwise tasty tidbits run in the opposite direction of our little Pigpens. If you feed these baby beetles non-stinky plants, they still make a poop force field, but because they have no deterrents to protect them, field ants will ignore the BM blanket and eat them right on up.

Slaving Away

It may seem like all fun and games for field ants, frolicking across our forests, lawns and traffic medians, grocery shopping and building their houses. But field ants have a wicked foe prowling those same forests, lawns and traffic medians, combing the grass for field ant nests: Amazon ants. Amazon ants look a lot like field ants. Same size, similar color, same big eyes, similar camel humpy back. Amazon ants and field ants look so similar they could sometimes almost pass as the same species, except one major exception: Amazon ants have dagger-sharp, sickle-shaped jaws. Their jaws are so pointy they can’t take care of their tender babies—any attempt at carrying or feeding could result in a fatal stab wound to their young.

So Amazon ants came up with a solution: They raid field ant nests, slashing and smashing adults as they go, snatch up hearty pupae in those jaws, and scurry back to their nests. Now, we remember from the ant’s life cycle that baby ants take a lot of food, but once those ants pupate, they don’t eat at all. They just sit there helpless in their nests and wait to turn into adults. By stealing pupae, Amazon ants basically snatch up adult workers that require no maintenance from the Amazon ants.

Once in the slave-raiders’ nest, field ant pupae’s bodies start to pick up the smells in the nest. Ants tell one another apart by smell. If a field ant starts to smell like an Amazon ant, she’ll start to think of herself as an Amazon ant. When she emerges as an adult, she does the tasks to help the colony that she would do in her real mother’s nest: gathering food, building the nest, raising babies, taking care of the queen. She usually has no idea that she’s a slave, helping her enemies to grow so they can raid more field ant nests.

During our summer, poor field ants are enslaved up and down the United States, from the forest near my North Carolina house to the parks of busy Long Island, New York. But you and I can still spot those lucky enough to escape the dagger jaws of the Amazon ants. They run along our tree trunks and across our sidewalks, planting seeds, snagging bugs, turning soil. We can look for their double humps and drop them a snack like a piece of a cookie or some juice from our juice boxes and see if they eat it. We can give them advice, tell them to stay away from poison poop and keep their big eyes peeled for slave makers. They can give us advice, too. They can tell us never to underestimate the power of small things, to be mindful of the good they can do. They can tell us that every animal has a complicated story, a life of adventure and trials that unfolds whether or not we humans pay attention. But you and I can pay attention. Field ants are happy to share their story with us.

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


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