I pruned a large passionflower plant which had been growing up the side of my house. I was struck by how much mess the snails had left on my (fairly) recently repainted wall. When I looked at it again about 1/2hr later there must have been about 20 snails making their way up the wall. I don't know where they were going but it was like there was a coordinated mission going on. Maybe they have a collective consciousness.