If you live near a hardwood, or deciduous, forest, you would have heard these by now; in fact, they may even be keeping you awake at night if you have a bedroom window open. The evening chorus is courtesy of the common true katydid (Pterophyla camellifolia).
True katydids are a key phenology species. Phenology is the study of timing of periodic events occurring in nature. I usually hear calls starting right around the last week in July to the first week in August; this year, I first heard katydid calls in Pike County around the second week in July.