On those infrequent occasions when the three-toed sloth climbs down to the base of its tree to deposit dung, sloth moths fly out of the sloth's fur. The female moths lay their eggs in the pile of sloth dung pellets. The moth larvae hatch and feed on material (e.g. undigested plant remains, etc.) in the dung or nearby plants. When they become adult moths, they fly up into the canopy and find a sloth in whose hair they live and hide.

There are 3 species of sloth moth, found only on three-toed and two-toed sloths. They are about one-third inch long with flattened bodies, and can move easily through the sloth's dense hair. The moths are preyed upon (both as larvae and as adults) by a wide variety of insect-eating animals such as predatory ants, antbirds, etc. The adult moths do not seem to feed on the sloth's hair. Any advantages to the sloth of the moths’ presence are unknown.