Does anyone know of a spider that is small and black, and has a shell-like butt?

Question

i see these spiders in the woods in PA. they usually have a long web stung across a path, and they are very small. there's this shell thing hanging off them whether its their butt, or a separate part of them, i don't know, but i think whatever type of spider they are it starts with an "m" does anyone know the name of them?? thanks.

Answer 1

Micrathena?

http://bugguide.net/node/view/1979/bgpag...

Answer 2

Learn to ID it yourself with the help of these sites-

http://bugguide.net/node/view/1954

http://www.arachnology.be/pages/Pictures...

http://www.spideridentification.org/