Armadillidium vulgare (Woodlouse).
 
 
 
Size: approx. 6-8 mm. Photo: 08/27/11, 11 am.


Woodlice are crustacean with a rigid, segmented exoskeleton and fourteen jointed limbs. They need moisture because they rapidly lose water. A. vulgare is an introduced species from Europe and common in the US. 
 

 
bug guide (the small photo):
http://bugguide.net/node/view/569018
wikipedia:
http://en.wikipedia.org/wiki/Woodlouse