Blepharisma feed on a variety of smaller organisms, including bacteria, flagellate algae, rotifers, other ciliates and even smaller members of the same species. Experiments with Blepharisma undulans have shown that cannibalism causes gigantism. When individuals are given a diet of smaller Blepharisma, or certain ciliates (particularly Colpidium colpoda), they grow to a relatively enormous size. As long as their diet remains unchanged, cannibal giants will divide to produce more giants. When large prey become unavailable, the offspring will revert to normal size.