They eat crops, which is why the humans fought them. They were a lot bigger back then, you can easily understand this if you compare a butterfly to a dragon. I'm guessing the use of pesticide is what have caused them to evolve into something so small, as smaller creatures are a lot harder to hit with spray.
A lot bigger? Were leaves that much bigger so that they could eat enough to survive?
I keep thinking if this was true, then the Wooly Bears
that people use to predict weather with, well if he's a dragon...then some people are still believing that they have the power to decide about winter, which IS a folk tale, or an old wives tale. So...that could in fact prove the existence of dragons...or maybe not. I think I'm now lost in the confusion of this discussion.