Inspired by the recent thread on Cactus photos for Wikipedia, I went to a location near Greenville where I had previously seen prickly pears, hoping to find them in flower. Shortly after uploading, they were identified as the southeastern prickly pear, part of the eastern prickly pear complex. I seem to have just missed the flowering season; there were a few dried-up flowers, but mostly green fruits. But instead, I found these really spectacular insects:
Link to observation: Cactus Coreid Bug (Chelinidea vittiger). There were so many of these that I think they are the reason the pads look yellowish instead of a healthy green.
As far as I know, all of the native cactuses in the eastern states are Opuntia, as is the one cactus species found in Canada.