Secondary pest: Scavengers
Acronym: PSO

Various species including:

  • Liposcelis bostrychophilus (Psocoptera: Liposcelididae)
  • Trogium pulsatorium; (Psocoptera: Trogidae)
  • Also Families: Lachesiilidae, Psyllipsocidae


  • Are quite small, 1 mm or less in length.
  • Larger pale booklouse can reach lengths of 2 mm, similar to some stored-product beetles.
  • Have very long, thread-like antennae and have an enlarged hind femur.
  • Are soft bodied and often translucent, varying in colour from black to white.

Similar species

  • May be confused with some larger species of predatory mites

Commodities affected

  • Animal and plant products, fungi
  • Stored grain, packaged food, glues, paper products, fabrics

Signs of infestation

  • Infestations develop in grain with moisture content higher than 14%.
  • Booklice are often associated with presence of moulds.


  • Is a minor pest of stored grain and does not damage sound grain
  • Damage is indistinct
  • Feeds preferentially on germ of broken kernels and on exposed endosperm of damaged kernels
  • Populations may be significant enough to cover walkways in elevators, creating a slipping hazard
  • May cause inhalation allergies and respiratory issues in susceptible individuals

How to control

Where found

  • Prefer moist, humid environments
  • Found in granaries, elevators, households, warehouses, processing facilities, museums
  • Are associated with high moisture content in stored grain and are found feeding at the tops of the grain bulk

Geographic range

  • Are found around the world and across Canada

Life history

  • Life cycle is incomplete metamorphosis with nymphs morphologically similar to adults.
  • Adults may be winged or wingless; nymphs are always wingless.
  • Adults prefer breeding conditions with high temperature and high humidity.
  • Generally, booklice require humidity higher than 60%.
  • Females lay eggs randomly in the food source.


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