This is Armadillidium vulgare, and the most descriptive English name is the pillbug (or roley poley!) and you can see that when it goes into defensive mode at the sound of a spider's footsteps, it could be mistaken for a pill. In the dark. After a bender. The woodlouse (#195) can not get into this tight ball (called conglobulation). Conglobulating is not only an excellent defensive mechanism, but also conserves moisture. This is very important when your respiratory organs or pleopods are on your ventral surface. One study (in Smigal and Gibbs 2008) found that pillbugs would spontaneously conglobate at temperatures above 40 deg. C. or when in very dry soil (< 10% moisture).
The females carry their eggs in a "marsupium" and even after they hatch, the young are carried until they are able to go into the world on their own.
A. vulgare was introduced from Europe to North America.
Smigel JT, Gibbs AG. 2008. Conglobation in the pill bug, Armadillidium vulgare, as a water conservation mechanism. 9pp. Journal of Insect Science 8:44, available online: insectscience.org/8.44