This is the Eastern Tent Caterpillar. You may not be familiar with what you see in this photo, but I’m pretty positive you’ve come across the “tents” they leave in your trees. In late summer, you’ll often find them gathered like sardines inside of large cotton candy like webs in your trees. I have a semi-repressed memory of dousing them in lighter fluid and…. well you get the idea. (I don’t condone killing any living thing anymore).
Oh, and here’s a fun fact. I can’t tell you how, but these have been suspected to cause horse abortions. Really. Seriously. Look it up. I dare you.