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Visual Reference Library - Insects
 IN-26.0 Psocids

Psocids (SO-sids)


Soft bodied insects, less than 4 mm long with long, slender antennae and chewing mouthparts. They may have four wings or be wingless. They are generally gray or brown in color. Psocids are readily identified (under magnification) by the presence of a large, conspicuous clypeus (nose).


Psocids live outdoors and have wings for the most part. They can be found on tree bark, tree and shrub foliage, and under stones. This type is known as “bark lice.” Psocids can be found indoors, and this type is extremely tiny and difficult to see. They are often referred to as “book lice” since they are common around old books in damp locations (such as the basement). This type is also wingless.


The female psocid attaches up to one hundred sticky white eggs to food. The eggs hatch into nymphs and will go through several molts before becoming an adult. In optimum development conditions the life cycle can be completed in as little as eight weeks. The adults survive for around six months. Psocids need to live in moist areas since they feed primarily on microscopic molds.


Psocids do not usually feed directly upon human food, but they will when there has been mold or fungal development within the food itself. Psocids are often found within dry products such as flour, bagged nuts, milk powder, chocolate, yeast, and stored cereal grains. They may also be found on books, furnishings, walls, and newly plastered surfaces which are still damp.

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Last updated May 2003