That is a slug. It will be one of your worst enemies in your yard. I suggest looking at ways to trap them..

In large numbers and in a moist environment, they can be quite destructive. On another note, slugs are more closely related to a clam then to an insect. They are quite closely related to snails.

This post was edited by smivies on Wed, Aug 21, 13 at 22:04

But thankfully these are slow. A way to get them all is to place a dish of beer as they are drawn to them and they will drown. Or use slug pellets to protect certain plants like hostas.. or use the rind of a watermelon as bait. Leave it out overnight and collect the rind and slugs in the morning. Destroy