the cast (shed) exoskeleton of an invertebrate. -OR- The sloughed-off skin or covering of an animal, especially an arthropod.

the cast skin of an arthropod (including insects).

cast skin of an arthropod, e.g. mite, spider, insect.

The cast-off skins or coverings of various organisms, such as the shells of crabs or the external coverings of the larvae and nymphs of insects.

cast-off skins or coverings of various organisms during ecdysis

the empty shells left behind after the adult emerges from the last larval stage. (technically, the shell left behind from any molt stage)

(sing. pl.) cast skin from any larval molt (including transformation into adult)