By John Woodmansee, Purdue Extension Educator

Ants are common throughout the world, and although some may stereotype them all as pests, they do perform beneficial work. Their tunneling aerates soils, and many species are predators of other insect pests. Ants come in varying colors – primarily red, dull yellow, brown and black. Some are quite small, like the Pharaoh ant at one-sixteenth of an inch, while others are up to one-half inch long.

Of course, ants can also be pests. And, some homeowners may currently be experiencing an ant invasion in their homes. Purdue experts Gary W. Bennett and Timothy J. Gibb offered additional insight in a Purdue Extension Publication they co-authored, simply entitled, “Ants.”

Bennett and Gibb said, “The best way to prevent ants from invading a house is to locate and destroy their nest.” They suggested looking in the soil around the foundation of the house, and if controls are needed, you can use appropriately labeled insecticides around the home’s perimeter.

Also look for ant mounds in the lawn. Ants actually provide a valuable role in turfgrass by attacking other pests, like grubs and cutworms. “Because of this, it is rarely advisable to treat lawns for ants,” they said. “Where ant mounds occur, however, they can be unsightly and may interfere with mowing.” To destroy mound-building ants, they recommended lightly soaking the mounds with a labeled liquid insecticide. “Use only formulations labeled for ant control in lawns, and follow label directions,” they said.  

If ants have gained entry into the house, Bennett and Gibb suggested applying insecticides where the ants gain entry or hide – at foundation walls, doorways, windowsills, baseboards, behind built-in cabinets and furniture, beneath refrigerators, and under other heavy appliances. A number of ready-to-use indoor sprays can be used for spot treatments. Ant baits are also available. Bennett and Gibb said, “You may have to try more than one bait to find one that is effective for your ant problem, and they may require 10 days or more to produce the desired effects.”

Of course, good sanitation should also accompany your ant control efforts. You may find that ants are foraging for some dropped and forgotten foodstuff, infesting stored food, or visiting an area with spilled vegetable oil or grease drippings.

One common question I get is whether an insect is an ant or a termite. Bennett and Gibb explained that ants have narrow “waists” like a wasp. A termite has a straighter body with no pinched waist. Winged ants have two sets of wings that are not the same length. Winged termites have two sets of wings the same length, twice as long as their body. Ants swarm all seasons except winter, while termites typically only swarm in the spring. And, if you want to look closely at the insect, ants have elbowed (bent) antennae, while termites have straight antennae.

Like termites, carpenter ants can present structural problems for homeowners. Carpenter ants are large black ants, winged or wingless, and up to one-half inch long. “They construct their nests in hollow trees, logs, telephone poles, posts, porch pillars, and other timber used in homes,” they said. “Their trademark is a small pile of coarse sawdust beneath their nesting site.” These nests are typically found in wood with a higher than normal moisture content.

So, carpenter ants hollow out tunnels and discard the sawdust, while termites actually consume wood. Bennett and Gibb said, “While usually not as serious as termites, they can weaken building structures.”

Bennett and Gibb said that the secret to control of carpenter ants is direct treatment of the nests. “Look for the piles of sawdust to locate the entries, then treat the ‘galleries’ by injecting spray or dust,” they said.

“To prevent carpenter ant invasion, spray foundation walls and adjacent soil with a formulation labeled for this use,” they said. “Exclude ants by sealing cracks and openings on the exterior of buildings, and by keeping overhanging branches trimmed away from the roofline.”

If using an insecticide on ants, be sure to note whether it is for indoor or outdoor use and follow all label instructions. For additional information, consult Bennett and Gibb’s publication on ants at: https://extension.entm.purdue.edu/publications/E-22.pdf