If their skin turns into a sort of plated armor, I also vote for some sort of beetle or fly larva- I can't think of any worms offhand that fit that description.
I was just talking to someone in my community garden last weekend about worms in compost, actually. There are the earthworms living naturally in most soil, and if you put your compost pile directly on the ground, they'll probably make their way into it on their own (unless the compost pile is too hot for them- then they'll hold off). But my friend was talking about using red wigglers, a somewhat different kind of worm. They're better at ingesting larger pieces of plant matter, and are better at quickly breaking the stuff down into what plants can use.
Peasant (1963-1972) and Fluffy (1970s?-1982- I think of you as 'Ambrose' now)- Your spirits outshone some humans I have known. Be happy forever.