The green-banded broodsac, scientific name Leucochloridium paradoxum, is a parasitic flatworm (or "helminth") that uses gastropods as an intermediate host. It is typically found in land snails of the genus Succinea that live in Europe and North America where it infects the host’s eyes making them appear as caterpillars that other birds prey on. Various birds consume these infected gastropods, becoming the definitive host for L. paradoxum to mature and release eggs in the rectum that are later found in the feces of the bird host.