I've never seen one of these out in nature in all my time in Minnesota. Apparently, you can find them in stagnant bodies of water and they are ferocious predators.
My wife had heard that if you use clear nail polish and apply it over the bite that it will help stop the itching. I didn't believe her at first, but what did I have to lose by trying it. Sure enough, within a little bit I realized I wasn't scratching at my legs or ankles anymore