We have many different species of ants in Iowa that live in different habitats and eat different foods. Only a small percentage of ants are what we would categorize as pest ants (meaning that they come into house occasionally for food or shelter). Some ants make colonies in the soil, and of these some prefer out in the middle of a lawn and others like to be under a rock or other object. Some ant species will form colonies in rotting wood. Many species are not terribly picky about where they set up home sweet home. Some species of ants, such as carpenter ants, are meat eaters. Their diet consists of proteins from other insects. Some ants prefer more sugary foods and many of them will feed on the honeydew of sap feeding insects.
With all the great variety in ant species commonly found in Iowa they do have one thing in common. They reproduce with winged swarmers. Swarmers are queen and king ants that fly out to start a new colony of ants. Once they have mated a queen finds a suitable habitat, begins digging out space for a colony, and lays eggs to produce her daughter, worker ants. It is interesting to note that the worker ants you see are all females, males just mate and die.
A well established ant colony may produce hundreds of swarmers. And all the ant colonies of the same species in an area produce swarmers at the same time. At some times of the year the air is full of winged ants. Most of us are fine with them outside, but become more concerned when we discover winged ants inside our homes. It is important to make sure it is a winged ant and not a winged termite. Termites produce swarmers as well and the presence of winged termites in a home is a strong indication that a colony of termites may be eating the wood of the house. See drawing below.
Finding ant swarmers indoors could indicate that there is an ant colony indoors, or it may just be a colony near the foundation of the house, or it may be that some species are attracted to lights at night. I always struggle a bit with what to advise people. It is easy when there are hundreds indoors because it means the colony is almost certainly in the house somewhere – in the walls, or rotten wood, or under the slab. Fewer than 10 swarmers and I usually tell people to keep an eye out for ant activity, but it is likely these were accidental invaders from an outdoor colony.
I do know that before any management is considered the first step is to properly identify the ant species. Just knowing it is a winged ant is a relief if you are concerned about termites, but it does not help at all in knowing if they are a species of ant that does form colonies inside homes, where to start looking for the colony, and what management techniques will be most effective in controlling the ants if there is an indoor colony. For ant identification please contact your local extension office or the Plant & Insect Diagnostic Clinic.