What kind of bug has 3 legs on each side of it's body by it's head, looks like a caterpillar, with ridges?

Question

Recently while in my basement, I have found several strange bugs. They were all by my bathroom down in my basement and looked kinda like caterpillars. They had 3 legs on each side, both towards the front of it's body by it's head. The mystery bug was about 2-3 inches long and was black with ridges along it. Does anyone have any clue what kind of bug this is? I'm clueless. Is there like a nest or something?

Answer 1

http://www.ipm.iastate.edu/ipm/iiin/node...

i dont know.... maybe it was that ↑ missing a few legs or .....

or does this look like it?:

http://davesgarden.com/guides/bf/showima...

thats the best i could do sorry =]