Scaly leg mites (Knemidocoptes mutans) are microscopic insects that live underneath the scales on a chicken’s lower legs and feet. They dig tiny tunnels underneath the skin, eat the tissue and deposit crud in their wake. The result is thick, scabby, crusty-looking feet and legs. The longer the mites reside under the chicken's leg scales, the more discomfort and damage they inflict; an unchecked infestation can result in pain, deformities, lameness and loss of toes.