Psocids
Order:
Psocoptera
Family: Liposcelidae
Species: Liposcelis corrodens and other species,
Trogium spp., Lachesilla spp., Psyllipsocus
spp., Psocathropos spp., Lepinotus
spp.
The psocids (so-sids), commonly called book lice or paper lice, are nuisance pests that inhabit humid areas. Despite what its common name implies, the book louse is not in the same order as lice.
This small insect is difficult to detect without the aid of a hand lens. When large numbers of book lice are present, tiny shadows cast by their small bodies may be seen by an inspector using a bright flashlight. Indoors, the psocids seek out damp, warm, undisturbed areas, such as inside books placed on shelves, moldy foodstuffs kept in a pantry, or stacks of stored slip sheets. Outdoors, these insects seek out protected areas, such as under tree-bark or leaves.
Biology
Psocids are generally colorless in appearance although some species may be grayish or light brown. The small body (1/25 to 1/12 inch in length) may support small, scale-like wings. The wings, if present, usually are held in a roof-like position over the body when at rest. The larger trogiid, Trogium pulsatorium, also called “deathwatch” due to the audible tapping motion of its abdomen, has brownish spots on its pale-colored body.
Psocids undergo gradual metamorphosis, that is the immature forms resemble the adult forms. The life cycle from egg to adult can vary greatly with each species and with seasonal and other local environmental conditions. Changes in relative humidity below a critical point may hinder development or cause death due to desiccation. Generally, development takes from four weeks to two months or more.
Psocids may feed on a variety of substances including molds, fungi, starches, and dead insects. Certain species will feed on the starchy glue and paste that binds books or adheres wallpaper to flat surfaces. Other species may feed on bulk grains that contain certain antibiotics of a fungal origin.
Control
Control measures should aim to reduce the relative humidity in infested areas to less than 50 percent to dry out infested goods and to eliminate mold, mildew, and other food sources for psocids. Supplemental ventilation will incase moisture evaporation, eliminating the humid conditions that support microscopic mold and fungi growth on packaging materials, grains, and other products. Equipment, flooring, and walls can be disinfected with appropriate cleaners to dislodge fungal growth. By eliminating food sources and lowering relative humidity, psocids will not be able to continue to survive in previously infested areas.
Several insecticides include booklice on their labels. Generally, a crack-and-crevice treatment is recommended in areas such as book shelves or storage racks where psocid activity has been observed. Products containing silica aerogel and other types of desiccants may help to reduce localized humid conditions.
(Courtesy of the National Pest Control Association.)