About every other day I find these little squigly white worms in the bottom of bucks hard plastic water pail. They are about the size of a pencil mark & an inch long. Sometimes just one or two, sometimes a small ball of them, always at the bottom. Every time I see them I empty the pail & sanitize it but they are back the next day. The girls rubber water containers never get any. This has me perplexed! The barn kitties have their own water; never any in theirs. Any ideas? No overhanging trees or foliage.