What to do about carpenter ants

A typical carpenter ant is often reddish brown or solid black and can be up to an inch long. | Photo by Jody Green, PhD

Carpenter ants are among nature’s most efficient insects when it comes to breaking down and transforming rotting or decayed wood into natural compost.

But what’s good for the environment is not always a welcome presence in the home.

“A lot of people don’t like bugs of any kind and consider them a nuisance when they see them in their homes,” said Dr. Jody Green, educator in urban entomology with Nebraska Extension, University of Nebraska – Lincoln. “These types of ants fall under the category of ‘wood destroying organisms’ and, while it can take time for damage to occur, people don’t like it when bugs damage their houses.”

There are many species of carpenter ants in North America, but all are recognizable by what Green describes as an evenly rounded thorax — the central body part on an ant to which the legs and wings are attached.

They also tend to be larger than other ant species growing to be up to an inch long. Depending on the species, they can be anywhere from a reddish brown to solid black.

Carpenter ants prefer to nest in dead wood – and that can include decayed trees, logs, firewood or rotted beams and sills in a home, Green said.

What signs should you watch out for?

As strange as it sounds, you may actually hear carpenter ants in your home before actually seeing them.

“They don’t eat the wood,” Green said. “But they excavate galleries and tunnels by chewing the wood with their mandibles and you can hear that.”

That faint rustling sound made by thousands of carpenter ants hard at work sounds a bit like what you hear when pouring the milk into a bowl of Rice Krispie cereal.

The ants reduce the wood to a course sawdust and that, along with their excrement, the bodies of dead ants and the remains of their prey, are removed from the nest and tunnels by the worker ants.

This powdery substance is called “frass” and piles of it on a table below an old beam, on the floor or next to a window can be the first visual sign of carpenter ants in the home, Green said.

It’s possible to live with carpenter ants nesting in a house for years and not even know they are there, Green said.

“A lot of times people first notice them when they see the ‘flyers’ in the house,” she said.

Carpenter ants develop wings and fly only during mating in what entomologists call “nuptial flights.”

Mating occurs when the colony sends out “breeders,” the  mature winged male and winged female carpenter ants to create a mating swarm.

“You may see them flying or crawling around inside your house,” Green said. “This is an indication they are breeding and that you have a mature somewhere colony in your house.”

How do you get rid of carpenter ants?

The most common reaction from a homeowner who spots a carpenter ant or two crawling around the house is to grab a can of insecticide and spray them.

“That’s really not an effective solution,” Green said. “You have only killed one or two ants from a colony of thousands [and] they will just send out more foragers.”

The most effective way to deal with the problem is to find and destroy their nest or colony.

“That can be difficult to do,” Green said. “The nest can be difficult to locate because they forage so far — the ants can be coming from inside your home, from your neighbors home, from the woodpile in the back of the house or from a rotted log [and] it can be hard to figure out.”

If the colony or nest is found inside the house, it’s best to call in professional exterminators to deal with it, Green said. They will have the proper equipment and be well trained in safe extermination methods.

Ants coming into a home to forage for food can be followed back to their nest, Green said. They often use utility cables or clothes lines to get from their colony to a house.

“They have a very well rounded diet,” Green said. “They do eat sugar, but also eat a lot of protein, which is why typical sugar ant bait does not work for carpenter ants.”

There are do-it-yourself carpenter ant baits available from hardware or farm supply stores that contain protein and other compounds they find palatable and may eat, Green said. These products can help stem the tide in the shorterm of ants foraging in your house, she said, but will not destroy the entire nest or colony. For that, she stressed, you really need to call in professional exterminators.

As far as any natural, non-chemical based method for killing off a colony, Green said she has not heard of any that are backed by solid science.

How do you prevent them from getting in?

To keep carpenter ants outside, Green said the best defense is a good offense.

“It’s really up to us as humans to seal off any places they are getting in,” she said. “It’s also up to use to make sure our homes don’t have any issues that attract the ants [like] rotten or damp wood.”

Green said you can also remove old, rotted stumps from around the house and make sure to keep your firewood supply away from exterior walls and piled on some sort of elevated platform above the ground.

It’s also important to keep countertops free of food crumbs or waste and make sure food is sealed up in airtight containers and securely put away so it does not attract the foraging ants.

“They can cause damage,” Green said. “How much depends how big the colony is, but it’s not the worst thing and you do have time to deal with the issue; it’s not like your house is going to fall down.”

Are they good for anything?

Carpenter ant damage in an old, rotted section of wood. | Photo by Jody Green, PhD

Carpenter ants do play an important role in an ecosystem, Green said

“If they were not around, they would not be breaking down old wood to create wood litter and compost and that would be unfortunate,” she said. “They also eat a lot of other bugs we consider garden pests.”

Carpenter ants are highly effective predators, Green said, with a very structured social organization.

“The females do all the work and they all have jobs to do,” she said. “Some take care of the brood and others forage for food and others take care of and feed the queen ant who lays all the eggs.”

All these “sister ants” take care of each other and communicate using pheromones.

While there are always a few males in the colony, the larvae only develop into males in high numbers leading up to the mating season.

Are carpenter ants dangerous to humans?

With their large, wood-cutting mandibles, carpenter ants can deliver a pretty good bite if threatened, and it can hurt, Green said. They also produce a form of acid they can spray as a defense.

“I’ve never been sprayed,” Green said. “But in talking with people who have I’m told it can be pretty painful on the lungs if you breath it in.”

For the most part, Green said, the carpenter ant just wants to be left alone to occupy its place in the ecosystem, regardless of if your home is in its path.

“We are the ones who make them a pest,” she said. “It’s not the ants’ fault we build our homes on top of their colonies.”

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