One night of succos my son jumped out of his bed in the succah startled. He was half sleeping when he felt a mushy thing in his hands. When he got up to check what it was he saw a slug. We turned the lights on and twenty minutes later we had captured 13 slugs of all sizes. We were shocked because we had never seen these before other that an occasional slug in the garden. We didn't know what to do. The next night we had some friends over who told us to pour salt near the succah walls because slugs are 90% water and they hate salt because it will melt them. This is why they also do not come out in sunlight.
Slugs are like the reshaim of this world. As long as they stay in their cozy shell in this world they are safe and protected. In the next world when they come out and face the truth that hits them like bright light, they melt away very quickly because their wholes lives consisted of nothing but vapor which cannot stand up to the bright light of truth.
Even in our own lives we often take a position that we put much thought and effort into justifying to ourselves. That's all fine and dandy until we are forced to face the real truth. Suddenly all the excuses and "bubba meisos" that we told ourselves for years disappear in one second and we feel really dumb.
The Slug sings: Kimo Shavlul Temes Yahaloich, Naifel Eishes Bal Chazu Shemesh; Like the slimy track of a slug which disappears; like the stillborn of a woman that does not see the sun.