Bagworm moth caterpillar. They live in a silk case covered with various plant items for camouflage. The case variation is kinda cool, as caterpillar cases mere feet apart can look very different because of the camouflaging material available.

http://bugguide.net/node/view/352578/bgp...

I found a ton of these bugs on my pathway and lawn. They looked like dead weeds until I got a closer look and noticed a black caterpillar like front sticking out of the weed looking part. They move very slow and are hanging all over my path lights. I have lived in Philadelphia my whole life and have never seen them.