Hairy caterpillar. Head-on view of the larva of a lepidopteran (moths and butterflies) with long hairs (setae, white) covering its body. Many caterpillars are covered in hairs that act as a defence mechanism. The hairs often have detachable tips that will irritate would-be predators by lodging in the skin or mucous membranes. Here, the caterpillar has an old exoskeleton attached to its head after a recent moult.