There are about 5,500 species of book lice and bark lice. Despite their names, these small insects are not true lice. There are many variations of bodies and wings among the species, which measure up to 1/2 inch. Book lice received this name because they like to eat the paste found in old book bindings. Bark lice are found on trees and feed on algae and lichen. They lay their eggs in foliage and the young are born as miniature adults. The nymphs molt about six times before they finally emerge as adults and their total lifespan is up to six months. They like to live in moist environments, do not bite humans and primarily eat dry, starchy materials.