Ants are insects related to bees and wasps (Order Hymenoptera). Of the 12,000 ant species worldwide, only about 50 become household pests. In North America the number is even lower. Ants do many things to benefit the environments where they live, including your home lawn and gardens. Before you grab the insecticide, consider whether they are truly a pest. Ants invading homes should be controlled, but ant colonies outside can usually be left alone, especially in lawns where they aerate the soil, remove weed seeds, and reduce populations of pests that feed on grass. The exception is fire ants, which are not currently found in NY.
Ants are easily distinguished from most other insects due to their elbowed antennae, lack of wings on workers, and their narrow waists which make the three body segments (head, thorax, abdomen) very distinct. Ants, however, are often confused with termites, which have a thicker waist and straight antennae. There are a few types of arthropods that mimic ants, but these are not common. Mostly, ants are confused with other ants and the differences between species can be stark or subtle – requiring a hand lens or microscope. This can be important because ants have different habits and food preferences that affect how they react to baits and efforts to remove them from inside buildings. To tell them apart, we look at the coloring, size, antennae, the petiole (waist) and the rear end. When ants swarm to mate and reproduce, kings and queens may look quite different from the workers. Kings and queens are called “alates” meaning they have wings, which are shed after mating.
Common ant species of concern
Light to dark brown, 1/8 inch (2-3mm) long, all workers are the same size, one node that is not visible from above, peculiar smell when crushed.
Dark brown, 1/8 inch (3-4mm) long, somewhat larger than odorous house ants, grooves on head and thorax give it a dull appearance, two visible nodes in petiole, stinger present.
Larger ants in general but variable in size from ¼ - ¾ inch (6mm to 19mm), variable color depending on species (all black, black and red, dark yellow), evenly rounded thorax and one node in petiole.
Allegheny mound ants
Head and thorax rusty orange, abdomen dark brown, 1/8 - ¼ inch (3-6mm), thorax uneven, single large node on petiole, no stinger but aggressive biter and will inject formic acid into wound, extensive outdoor colonies with very large mounds common.
Pale to reddish brown, 1/16 inch (1-2 mm), very tiny and hard to see, petiole with two nodes, easily confused with thief ant. They will nest indoors and trail near food and water.
Color variable from light yellow to dark brown, 1/16 inch (1-2mm), very tiny and hard to see, petiole with two nodes, similar look to Pharaoh ant. Often seen trailing near food source.
In outdoor environments, ants are quite beneficial to the environment. Many species are scavengers that clean up dead animals, decaying food, sap, and even crumbs in your house. Their colonies can form complex and extensive tunnels that provide pathways for air and water to reach plant roots. Ants carry seeds back to the colony, often resulting in seed dispersal and germination. Some ants will eat termites. And ants are the favorite food of many bird species such as woodpeckers, and other animals. When living in the yard, garden, farm field or forest, ants are beneficial.
Although ants are important in natural habitats, they often present problems for humans in the built environment. Some ants invade termite or water-damaged wood in buildings, causing more damage. Others can contaminate food, equipment and sterile environments (food plants or hospitals). Ants that nest under objects can undermine surfaces made of stone and concrete. Some species of ants have painful stings and others may bite and even spray formic acid into the wound, resulting in more pain. Only a few species are responsible for the harm associated with ants.
Ants live in colonies underground, in rotting wood, inside trees, leaf litter, under bricks or patio stones, or in other moist, protected places. Carpenter ants are more neighborly. They’ll set up shop in your home if they need space or if water or water-damaged wood is nearby. Smaller ants may also create nests in cavities, such as walls or roof eaves, and spaces all around the building. And several ant species create numerous satellite nests that are related and connected to a larger central nest. Ant colonies can be small, but most pest ants create large colonies of tens of thousands of workers and some species have hundreds of egg-laying queens. It is important to note that you may see ants trailing indoors, but they may not be nesting indoors. Often ants are only foraging for food and water inside, while the nest is located outside. It may be possible to learn where the ants are living by providing food (something visible to you that they can carry) and watching the ants head back toward the nest. Cooked rice, cracker crumbs or granola may work for this.
Ants eat just about everything from honeydew and nectar to dead animals, live insects and their eggs, fungi, seeds, oils, and more. Their diet changes seasonally to accommodate the nest life cycle and this information can be used for more successful baiting in a control program. For example, ants may prefer sweet foods in the spring and protein-rich foods in the fall.
Ants, in general, can be difficult to control permanently inside a building because they can be so numerous and widespread outside. Correct identification is key to creating a management plan. Options for control include the following with examples:
Sanitation to reduce attractive food and water indoors and sometimes outdoors
- Food and drinks, spills and crumbs on the counter, floor, in the garbage can, and on used dishes can attract ants. Kitchen sanitation is key to avoiding ant problems.
- Examine shrubs in the landscape for aphids and scale insects that produce honeydew; consider removing and replacing infested plants to reduce ant food
- Funnel rainwater farther away from the foundation using downspout diverters or splash blocks
- Avoid feeding pets where ants can find the food
Exclusion - keep them out of your space
- Replace uneven or broken garage door bottom seal
- Make sure doors and windows seal well when closed
- Repair and seal openings around the foundation, roof edge, and where utilities enter (electric, plumbing, etc.)
Habitat modification to reduce their activity in an area
- Remove stones and landscape timbers in the perimeter of the house or building to reduce nesting nearby
- Cut grasses, vines, trees and shrubs off of, and at least 6 inches away from, the structure
- Very effective ant baits are available in hardware stores and online. Follow this guidance for choosing and using the right product. We do not recommend homemade baits.
- Barrier, perimeter, and direct insecticide treatments of ant nests are effective when done correctly. Drawbacks to insecticide use include risk of pesticide exposure for people, pets, and beneficial animals like pollinators. Hire a professional for the job, or follow label instructions when doing pesticide treatments.
Each species of ant has different habits and requires a different approach. Control begins with accurate identification and understanding why they have become a pest. With this information you can choose a control strategy.
For more information on ants, we were joined by Karen M. Vail, University of Tennessee, to speak in our NYSIPM Academic Seminar Series. She gave a presentation titled, Urban Ant IPM: It starts with an "eye".