It’s difficult to tell, but this mound of earth and ants is 19 or 20-inches high and as big around as a bushel basket. We discovered after some of the snow disappeared at the side of our backyard. Although the mound wasn’t there last year, there might have been a much smaller colony under a low-growing evergreen bush. Photos by Victoria Metcalf

Welcome to the beneficial ant world

When February’s snow started melting in our backyard my husband Tom called my attention to a large mound he’d discovered.

“Have you ever seen this before?” he asked.

From where I stood on the back porch it looked like it was made up of dirt with some pine needles scattered in.

“They’re ants,” he said.


I went over to look and sure enough we had a mound of earth that contained thousands and thousands of red and black bi-colored ants. It was gross.

I was also concerned about my 5-year-old grandson deciding to play in the mound, and our pets.

I called the Plumas County Department of Agriculture about what to do. Their best guess, based on my description, was that they were carpenter ants. That wasn’t good. I didn’t want them migrating into my house. I didn’t want them setting their little jaws to work on all the wood.

These beneficial red and black harvester ants seem to come out of their mound at daylight and then plug the entries at night. I happily discovered a large entryway right after reading up on the two dozen or so different varieties of harvester ants. But the following day that entryway was apparently blocked and others were being used. Oddly, the mound and surrounding area have become a source of interest as I try to determine where they’re going and what they’re after.

Tom and I discussed what to do. He looked at some of the products recommended to rid us of what we thought were pests, but eventually we decided the job was just too big for us to take on.


We contacted a local pest control company and a man came over the next day. They’re not carpenter ants, he explained, they’re beneficial harvester ants. And they’ll move or go away completely when their food source is gone.

The exterminator, someone named Lee, visited the house the day after Tom contacted him. Harvester ants are beneficial, he said. They don’t get into the house. They don’t eat the wood.

They’re usually attracted to a fungus that appears in woody stumps, he explained. And they must have found some where they built their mound.

But what about all of those ants that aren’t busy climbing all over the mound, I wondered as I saw dozens of them going to and froe toward some low-growing evergreen bushes.

It turns out, according to Lee, that they also eat bugs. He didn’t specify which bugs, but a web site said they are particularly fond of roly-polies, those roundish, armor-plated, brownish bugs that seem to infest flowerpots and garden soil. They’re probably best known for rolling themselves into a tiny ball if bothered. In fact graveyards of husks will mark a harvester ant area when there isn’t a mound to readily identify their habitat.


Near the entrance to the nest is an area called the midden. This area will vary in diameter depending on the diameter of the mound itself. The midden is the “trash dump” for the colony. It is where the ants deposit pebbles, dead workers and unusable matter from plants and animals brought in by foragers, according to John M. Davis of the Texas Parks and Wildlife Department about harvester ants.

“Though they are mostly seed eaters, they will take animal matter as well. This includes lice, screwworms, maggots, ticks, mites, snails, worms, millipedes, silverfish, spiders, grubs, beetles, other ants, termites, fire ant alates, and many other small insects unfortunate enough to get caught. They are also known to eat feces of animals,” according to Davis.

Typically, a colony sends out scouts that detect food sources. They go back to the nest and let the foragers know what they’ve found. It’s the foragers who bring the seed or bug back to the nest. These ants can go up to 130 feet from the nest to gather food, Davis explained.


Each colony has a single queen that is long-lived by insect standards. The Florida harvester ant queens have lived up to 17 years. Those of the Idaho harvester ant variety average that long, but have also been know to live for 30 years.

Problems with the ants could occur if they infest a lawn. They tend to leave a bare spot around the nest. They also bite or sting.

I guess it was one of the scouts who determined at some point that our yard was a prime location.

Since they’re beneficial ants, we’ve decided to leave them alone. Their nest is in an area that we don’t use much. It used to be part of a pathway, but an apple tree nixed the path.

The interesting thing about these ants is that once they went from being a terrible ant to a beneficial ant my attitude changed. I now find them fairly interesting. I just wonder how long they’ll stay and where they’ll decide to go next.