Summer of '98 or '99, we had cicadas in the southeast similar to a swarm of locusts. Honestly I don't remember what they did to plants, if anything. What I remember was that they covered everything. I was 13 or 14, and the local putt putt place would pay me and my buddy to clear the course and water features of cicadas. Did that everyday for weeks. It was pretty crazy. They are terrible fliers, and they love things that make noise. Watching someone operate a mower or any kind of equipment was always entertaining, they would swarm in a huge cloud smacking into anything and everything.
At first they are terrifying. They're big bugs, probably 2" long, 1/2" diameter, big ass red eyes, and a giant set of wings. They look like something out of a horror movie, and they make all kinds of racket. But they don't bite. Like I said, they are terrible at flying, so they'll smack right into your face. It was summer so I was always at the creek fishing, and they were almost like a blanket on the water. That was the 13 year cycle I believe. 2011 wasn't really bad, kind of strange, but Cicadas are strange. It seems like their purpose is simply a bonus buffet from nature.