Now that winter is here, it's nice to remember green pastures. A few days ago, while I was at a place we call "The Landing", I saw this one on the propane tank.
This is a close-up view of the propane tank's algal pasture land. The meandering trails are the feeding marks of slugs or snails. They move their head from side to side as they slime along, rasping up the algae with their radula. Here's an even closer look.
Just think who passed this way last summer. The little snail's house on the Prairie.
A great resource for more signs and tracks of invertebrates, is the book