Facts, Identification & Control

Latin Name

Order Psocoptera


What do they look like?

There are more than 200 species of psocids (often pronounced "so-sheed") in the United States. Most psocids are tiny insects.

  • Size: Depending on the species, the size ranges from 1 to 6 mm.
  • Color: The color of psocids varies according to the species.
  • Wings: Psocids that live outdoors often have wings. Psocids that invade homes usually have very small wings or no wings at all.

Psocids have chewing mouthparts, but they do not bite people or pets. When they invade kitchens, they can contaminate open packages of food.

How Did I Get Psocids?

Psocids, also called book lice although they are not truly lice, live in warm, moist places. They feed on mold or fungi and if found in decaying organic material, as well as grains, insects, and starches like book binding glue it is the result of psocids eating the mold and/or fungi growing on these items. Psocids are common in humid climates and poorly ventilated areas in homes. Damp cardboard boxes, books, papers, molded wood and leaking sinks often attract the pests.

How Serious Are Psocids?

The presence of psocids is merely a nuisance because the pests do not harm humans or pets and do not bite. Large populations usually indicate an underlying mold or moisture problem. When homeowners spot them near stored food in pantries, the pests are an indicator of food spoilage. If items are infested by psocids, throw the items away and take steps to reduce the humidity and moisture in and around other, non-infested foods.

How Do I Get Rid of Them?

Make a careful inspection to find the moisture sources. If psocids are active in the kitchen, start the inspection under the sink. Empty the cabinet if necessary. Inspect every area that has plumbing. In the bathroom, there should be a trap door near the head of the bathtub for access to the pipes. Inspect tile walls carefully. If grout is missing, mildew can grow behind the tiles.

There can be other moisture sources besides the plumbing. Look at the gutters and downspouts. Make sure they are not blocked. Downspouts should drain away from the foundation.

Check the crawlspace vents. They should be open in warm weather. If there is moisture on basement walls, specialists at the home store can recommend ways to waterproof them. A dehumidifier can also help reduce moisture in a basement.

The Orkin Man™ is trained to help manage psocids and similar pests. Since every building or home is different, your Orkin technician will design a unique program for your situation.

Signs of a Psocid Infestation

The main sign of psocids is the sighting of the psocids themselves on surfaces or in products. Psocids often seem to appear suddenly. This may be because they are so small that people do not notice them when there are only a few around. Some people think psocids look like tiny termites.

Behavior, Diet & Habits

Psocid vs Book Lice

Some people call them barklice or booklice. The name barklice probably comes from the fact that outdoors they gather under the bark of trees. The name booklice comes from the fact that they gather on moldy books in damp homes. Experts think that the sizing and starch in the bindings of books supports mold growth in humid environments.

What do they eat?

Psocids are tiny insects that live in damp environments. They eat mold and mildew.

Where do they live?

Psocids invade areas where there is dampness and mold, like basements and crawlspaces. They also infest areas where a plumbing leak causes mildew or mold to grow. Psocids have infested bath traps with leaking or sweating pipes. They have also infested air conditioning drain lines.


Psocids cannot retain water in their bodies, so they are sensitive to changes in humidity. A key step in controlling psocids is reducing the humidity in their environment. When the humidity is low, the psocids will die. If the humidity stays low, they will not reinfest.

Reproduction & Life Cycle

The females lay eggs in the spring and summer. The immature insects are called nymphs. They look like the adults but have no wings.

More Information

Although people call them booklice, psocids are not really lice and do not feed on blood. They are insects in the order Psocoptera.