Psocids are small insects belonging to the insect Order Psocoptera. They are often called barklice or booklice. Most of these insect species are free-living. A diminutive number of species, mostly belonging to the genus Liposcelis, are pests.

These insects are common household insects and are harmless. Their size varies from one to two millimeters and they feed on dry foods (powdery type). The variety of food they could eat could either be dry food products (cayenne pepper, flour, etc) and molds that usually develop in wet, humid conditions.

There are several types of Psocids. These insects are seldom found in places where food is manufactured. Contrary to popular beliefs, having these insects in your home does not mean the homeowners have poor hygiene. Psocids have no preference as long as the location is dark, humid, and warm. You can likely see them in the folds of food packaging in the cupboard. Psocids have a lifespan of up to six months. The female Psocids can lay a maximum of a hundred eggs during her lifespan.

Psocids that have wings can mostly be found outdoors (tree bark, under stones, foliage). These Psocids are commonly called barklice. Barklice feeds on a variety of plants including lichen, fungi, pollen, organic materials and decaying plants. When grouped together, these barklice are noticeable. Although they feed on plants, these insects are harmless and there is no need to control them.

Psocids that do not have wings are called booklice. An example of this type of Psocid is Liposcelis spp. These Psocids feeds on fungi, molds, insect fragments, grains as well as starchy materials like glue found on book bindings. They rarely inflict damage inside buildings but can be a problem when they occur in large groups.