Sloth moth is a generic term used to refer to coprophagous moths which have evolved to exclusively inhabit the fur of sloths and to use sloth dung as a substrate for the early stages of reproduction.
Certain lepidopteran moths snout moth family Pyralidae (namely subfamily Chrysauginae) have evolved to inhabit sloth fur exclusively. Typically, sloth moths follow a life-style broadly on the lines of Cryptoses choloepi, a moth in the snout moth family that lives exclusively in the fur of the Brown three-toed sloth Bradypus variegatus infuscatus. Adult female moths leave the fur of the sloth to lay eggs in the sloth droppings when the sloth descends, once a week, to the forest floor to defecate. The larvae of Cryptoses choloepi live in the dung and newly emerged moths later fly from the dung pile into the forest canopy to find a host sloth.[1][2]
Chrysauginae moths, such as Cryptoses spp., spend their lives as adults in the fur of sloths, particularly the three-toed species, except when the sloths went to defecate and females flew to the sloth dung to oviposit. An imbalance in population sex ratios favouring males has been noticed and surmised as female moths not making it back to host sloths after ovipositing.[3]
Sloth moths are considered to get nutrients from the secretions of the sloths' skin and/or the algae present on the fur as well as protection from avian predators.[3]
Some three-toed sloths have been recorded carrying more than 120 moths in the fur of an individual sloth. Two-toed sloths are recorded as harbouring lower populations. Several different moth species may coexist on the same animal.[3]
Lepidopterans belonging to the coprophagous guild that are specialised to live around sloths include: