Eastern Zigzag Salamander
Plethodon dorsalis dorsalis

Union Co., Illinois. October 1983.
 

Here's a nice Zigzag from southern Illinois.  Under the next rock you might find a dorsalis that looks identical to a Redback Salamander, Plethodon cinereus, that is, sans zigzags.  The third rock over may shelter a Leadback Zigzag, with no pattern and a dark grey color with silvery grey flecks.  Salamander identification is difficult at best, and sometimes all you can do is rely on the range maps in your Field Guide.

Below is a dorsalis from central Kentucky.