Searching for an animated cartoon seen on the "Junior Frolics" show of the 50's with Fred Sayles - possibly a stop-action type animation featuring ants and a snail. The snail, as I recall, had bulldozer type treads for locomotion.

Found some interesting info about Fred Sayles' show here:
Uncle Fred Sayles
They reference 'Gumby" type shows (stop motion), called George Pal's Puppetoons (later named Madcap Models.. I think?) - anyway, maybe this can get you on the right track to find what you're looking for.. I looked up some of the puppetoon shorts available on YouTube, didn't see any with snails or ants though... good luck!