I always save lots of time just chopping a couple of dozen or so in half for the other slugs to eat, they get full on their friends and leave your crops alone. I put bran down as well, they gorge on that and sometimes pop :D
Robert, I think the carnivorous slug is the Leopard slug, its markings are very pretty. It hunts down and eats slugs, Im not sure though if its slightly omnivorous ???