Booklice belong to a large group of small to medium sized insects called Psocoptera. Also known as psocids, booklice are related to plant insects called barklice. Though booklice may have a body shape similar to a louse, that is all they share in common. They do not bite people or pets. However, they are suspected to aggravate asthma attacks.
Booklice are widely distributed throughout the United States. Most are small, up to 1/4 inch long, soft-bodied and vary in color from yellowish-white to pale grey. They are found indoors and are wingless.
Booklice females only mate once, while males may mate with several females. The eggs are usually laid on paper or food products. Young booklice look like miniature versions of the adults. The average booklouse takes about one month to develop from egg to adult. Adults can live an additional three months.
Booklice depend on warm temperatures and humidity to survive. Ideal temperatures and relative humidities for survival range from 75-82°F and 75-90% RH. They are negatively affected by low humidity (50-60%) and can die within weeks if levels remain low.
Large numbers can build up in a short time. They feed on molds, and a variety of animal and plant matter and are often found feeding on papers or books with mold, dead insects, animal and plant specimens, flour, grains, cereals, and dried fruits. Booklice, damage damp books when they feed on moldy paper and starchy glue used for binding and may also damage paper if their bodies are crushed. Sometimes, booklice build up to large numbers in newly constructed buildings. Freshly applied plaster and drywall may contain high amounts of moisture that can support mold growth.
Control of booklice is best achieved by reducing humidity in a building to a level below 50%. Low humidity prevents most mold growth and directly kills booklice. Food items supporting mold growth should be removed. Thoroughly clean the infested area. Correct leaks or moisture problems. Store books and paper in well-ventilated, non-cluttered areas. Chemical control of booklice should not be necessary. These insects, while easily killed with insecticides, are often resting in locations that are hard to treat and humidity control alone can be very effective.
Originally published 03/04