Adult male scales are tiny 2-winged insects. Eggs of the European fruit lecanium are white, and crawlers of both species are light colored. Immature female scales overwinter on the bark of twigs and limbs, usually being more abundant on the underside. They resume feeding in the spring and mature during May. During June the terrapin scale produces crawlers, whereas the European fruit lecanium produces eggs which hatch into crawlers.
Crawlers migrate to the underside of foliage to feed for about one month.
Female scales return to the bark of twigs and limbs to continue feeding, whereas males usually mature on foliage and emerge to mate with females. There is one generation of the terrapin scale and one or two generations of the European fruit lecanium per year. Where infestation is severe, twig and limb death may occur as feeding scale remove sap from the tree. A more common problem is the discoloration of fruit and leaves from a black sooty mold which grows on the honeydew produced by feeding scale. A thin coating of petroleum jelly will enhance and extend the tape's effectiveness in capturing crawlers.