Booklice (Psocid)

What it does

Booklice are tiny, quick, soft-bodied insects that scurry across damp surfaces feeding on microscopic mold. Despite the name, they are not true lice and are unrelated to head or body lice. They do not bite people or pets. Their populations grow fast in humid conditions and drop sharply once the air dries.

Where it lives

They thrive anywhere humidity is high and mold grows: damp books and paper, cardboard, wallpaper paste, window frames, and pantry shelves. They are common in new homes where plaster and framing are still curing, and in stored grain, flour, and cereals. Indoor pest species are usually wingless.

How it breeds

Many indoor booklice reproduce rapidly, and some can reproduce without mating. Females lay small eggs in cracks and on stored items; nymphs resemble tiny adults and mature in as little as two to four weeks in warm, humid conditions. Multiple overlapping generations occur each year, especially in summer.

What it eats

Booklice feed mainly on mold, mildew, and fungi, plus starchy materials like paper, book bindings, wallpaper paste, and grain dust. They are drawn to stored foods more for the mold on them than the food itself, though they can infest flour, cereal, and other dry goods.

Identification

Booklice are very small, about 1-2 mm, and pale gray, tan, or nearly translucent, so they are easily mistaken for moving flecks of dust. They have a soft body, a relatively large head, long thread-like antennae, and, in indoor forms, no wings.

Signs of an infestation

• Tiny pale specks moving across books, paper, or damp walls
• Insects in stored flour, cereal, or grain, or on pantry shelves
• Sightings near mold, mildew, or condensation
• Presence in new construction where materials are still damp

Prevention tips

• Keep indoor humidity low with ventilation and a dehumidifier
• Store dry foods in airtight glass or plastic containers
• Discard or dry out moldy books, papers, and cardboard
• Fix leaks and condensation on windows and pipes
• Improve airflow in closets, pantries, and basements

Professional solutions

Booklice seldom need professional treatment. Reducing humidity below about 50 percent usually eliminates them within days by killing the mold they eat. Insecticides are rarely necessary. Persistent infestations, especially in stored food or a business, may warrant a pest professional to find the moisture source and check for contamination.