Hermit crabs produce solid waste. They defecate into their shells. At intervals, they clean the waste out of their shells, depositing it on the ground. Individuals who keep hermit crabs as pets have to routinely remove the waste from the crab's enclosure.
Hermit crabs live in shells, but they do not grow their own shells. Instead, they borrow the empty shells of snails or whelks. Hermit crab abdomens are soft and need the protection provided by the borrowed shells. The anus of the hermit crab is located at the end of the abdomen. Because the borrowed shell was grown to fit a different animal, it does not have a natural opening through which the hermit crab can empty solid waste.