Louse
2 of the 7 encyclopedias on this shelf carry an entry for Louse. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
a parasitic insect infesting man and beast. True lice are wingless and have soft, sucking mouth parts, suited for drawing blood. Three species infest people. One lives in the head, two live on the body. A related species infests the horse, another the cow. Stockgrowers plunge their animals into a tank of tobacco water, or spray them with an infusion of tobacco or an emulsion of kerosene. Lice are often so numerous on an animal as to keep it poor. Bird lice or chicken lice differ from true lice in having biting mouth parts by means of which they feed on wool and skin, but chiefly on feathers. Fowls and birds wallow in the dirt and take a dust bath to render their feathers an impossible living place for lice. Book lice are small, pale, black-eyed lice that hide in books and feed on paper. They are classified near the bird-lice. The true louse glues about fifty bean-shaped eggs to a hair. These nits, as they are called, hatch in six days, and in eighteen days more they are full grown. With a fair degree of prosperity, therefore, for forty-eight days, the descendants of a louse colonist may have passed the thousand mark.
Collier's New Encyclopedia (1921)
the genus Pediculus. The sexes of lice are distinct. The female is oviparous, producing eggs, popularly called nits. The young are hatched in five or six days, and in 18 these are capable of reproduction. Three species are Pablite reproduction. in certain circumstances on man. The body or clothes louse, Pediculus corporis or vestimentorum; the head or common louse, P. capitis; and the public or crab louse, P. pubis. The first species lives in the folds of the clothing in some elderly and uncleanly people. It has the abdomen three times as broad as the thorax.