In some species there are no lungs, some have 2 pairs of lungs and some have 5 pairs. These lungs appear as white patches on the underside and can be seen with the naked eye. The number of lungs helps to determine the amount of time that the woodlouse can spend away from its damp shelter. It is possible that they also take in water by absorption through the cuticle. Any excess water can be removed from the body by pressing the uropods together to form a tube which is pressed against a dry, absorbent surface and the water is lost through reverse capillary action.
Water also leaves the body by transpiration through the cuticle and with the faeces.
The temperatures that individual species can tolerate vary, generally it is between -5C and 42C, species from damper habitats can tolerate less of a change. Most woodlice, except the very old, are nearly always in some active stage of moulting. This continues throughout the life of the woodlouse whilst it is actively growing. The whole skin is shed, half at a time. Before the skin is lost it loosens, making the animal appear whitish over half of the body.