@cf82808b the male turns into a moth. The female stays a worm and makes this bag to lay eggs in. It attaches it to the trees and disguises it to look like a pine cone. It lays up to 1000 eggs in that bag. They hatch in the spring and eat the trees. One of our trees is dying from them. I had never heard of them either until I saw this in my driveway.  I had to google it to see what it was. My husband pulled about 60 of them off one tree in front of our house. 

 @44d466f2 Holy crap. I thought the hornworms on my tomato plants were bad.