The brown-banded broodsac, scientific name Leucochloridium variae, is a species of a trematode whose life cycle involves the alternate parasitic invasion of certain species of snail and bird. While there is no external evidence of the worm's existence within the bird host, the invasion of the snail host involves the grotesque swelling of one or both of the snail's eye stalks as well as the takeover of the snail's brain. This invasion does not cause the snail's death, and snails who are thus invaded sometimes actually live longer than those which are not.