Booklice belong to a group of insects collectively called psocids (sō΄ sids). The psocids are small, soft-bodied insects, ranging in color from a translucent white to gray to light brown. They are usually less than 1/16 inch long (1.5 mm); however, outdoor species can be 1/4 inch (6 mm). They are both winged and wingless, and they have long, filamentous antennae. Psocids have chewing mouthparts and a bulging clypeus — the front part of the head — between the eyes.
Psocids’ primary food sources are fungi, cereals, pollen, fragments of dead insects, or other similar materials. They cause little loss by actually eating foodstuffs since they do feed chiefly on mold. At times they may become extremely abundant and spread throughout an entire building, where they prefer warm areas with high humidity. In such situations they may contaminate foods and materials to the point the goods must be discarded. Damage to books may be more direct as they eat the starch sizing in the bindings of books and along the edges of pages.
The majority of psocids are outdoor species with well developed wings. They are also referred to as “barklice” because they are commonly found on bark or on the foliage of trees and shrubs. Most of the species found in buildings are wingless. Because they are often found among books or papers, they are called booklice. The term “lice” in the names is somewhat misleading because none of these insects are parasites and few of them have a louselike appearance.
During the warm summer months, the psocid female can lay 50 to 60 eggs. The eggs of psocids are laid singly or in clusters and are often covered with silken webs or debris. Most species pass through six nymphal stages. The entire life span from egg to adult is between 30 and 60 days.
Reduction of moisture (humidity) to less than 50% can eliminate the formation of molds and is the most effective method for controlling booklice. Infested furniture, bedding, or other movable furnishings should be thoroughly cleaned and aired. Infested foodstuffs should be discarded. Clean up spilled food products and keep all stored products in tightly sealed containers.
Chemical control is not usually necessary once moisture has been reduced. However, if an insecticide is required, apply a spot treatment or crack-and-crevice treatment using a product labeled for crawling insects or booklice and apply it according to label directions. Mothballs containing naphthalene or 1,4-dichlorobenzene can be used in areas where it is not possible to reduce humidity, such as basements, closets, and storage areas. Always follow insecticide label instructions carefully.