A Copper Underwing Caterpillar, Amphipyra pyramidea, was nibbling on our native plum tree. It's a pretty blue green color that stands out against the foliate. It's a hefty sucker too. Perfect for fishing, making some bird happy, or just turning into a boring brown moth. They feed on assorted fruit trees, and hardwoods. I read they only have one generation each year and over winter in the egg stage. Considering it's May I guess one generation means females lay continuously over the summer, because it's hard to see the adults just waiting for fall.