What does it mean when a snail has black lines in the middle of its shell?

If you have a pet snail, or have seen a snail in your garden with crust on the hole of it's shell, well, first, good job at being so observant! What you have discovered is a snail in hibernation! Yes, believe it or not, snails do hibernate. Like bear, squirrel, and bobcats, some snails fatten up in the summer and burrow down in the dirt to escape the cold winter months. The snail will sustain itself on the extra fat they've stored. Once the snail has burrowed down, it (most snails are girl and boy at the same time, like flowers) will make a white, crusty layer over the opening of it's shell. HAve you ever noticed a trail of slime behind a snail? They use that mucus to cover the opening of their shell, and then it hardens. When Spring comes, the snail can simply knock the crust out with their head, and enjoy the world once again. Sometimes, a snail will go into a slight hibernation, called estivation, when condtitions are not the best for them. Then, the mucus coat will stay moist and not harden.