Every spring we get large winged ants in the house. We can't find an entry point. They are in the basement and on both floors of the house. What can we use to get rid of them?

I would take some of these to your county extension office and make sure that they are not termites. I speak from experience!

WallyH

WALLY'S right. Termites look similar to ants in their winged states. To distinguish between them, check the wings or the waist. A termite will have four wings that are close to equal in size, and termites drop their wings readily. Winged ants will also have four wings but the front pair are longer than the back pair. Ants have a pinched waist, whereas termite are thick waisted. Termites can get larger than ants.

Ants and termites with wings are the reproductive stages that emerge, often in response to spring rains, from the colony to start new colonies in a new location.

Termites are more of a problem. You may have ants or termites living in, or under your house. The best solution is to get rid of the nest. Unfortunately, if may be difficult to find the nest and with termites, you might have to seek a professional (and expensive) solution.

Ant biology, ID & control (http://www.ipm.ucdavis.edu/PMG/menu.ants.html)
Termite biology, ID & control (http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7415.html)