• Size: Range in size from one-twenty-fifth to one-thirteenth of an inch.
  • Color: Cream colored to pale white.
  • Behavior: Most psocids live outdoors, have wings as adults and are commonly found on or under the bark of trees. These outdoor species are known as “bark lice.” The psocids found indoors are extremely tiny and difficult to see. They are wingless and are common in moist or damp areas. They are known as “booklice” because they are often found in association with old books stored in damp conditions such as in a basement. Unlike true lice, however, psocids do not bite and are harmless. Psocids feed primarily on microscopic molds; therefore, they need to live in moist situations where such molds can grow. They can be found in most buildings but are rarely seen in homes as pests. Homeowners, however, may occasionally capture one and ask a pest professional to identify it.


Psocids can be found outside under bark, in logs, under stones and within leaf litter. They occur in houses, warehouses, museums, libraries, in stored foods and many other types of buildings. Psocids prefer damp, warm, undisturbed situations where microscopic molds thrive.