ABSTRACT
The insects of the order Psocoptera are commonly called psocids. Out-door forms on tree trunks and branches have been called bark lice, and in-door forms, sometimes found in old books, have been called book lice. A detailed description of these insects is given in the diagnosis. Suffice it to say here that they are small, usually soft bodied. The body and forewings are commonly shades of brown or gray. Some domestic and cave-dwelling species have no pigment in the body wall, the muscle and fat of the subcuticular layer showing through the cuticle as creamy white. The unique mouthparts (see diagnosis) set this order apart and indicate a close relationship to the Mallophaga, hence, probably in turn to the Anoplura. These three ‘louse’ orders are probably hemipteroids, as they share with the other hemipteroid orders a low number of tarsomeres — not more than three —, absence of cerci, and a well developed cibarial pump apparatus, which in psocids and Mallophaga appears to be involved in water uptake from the atmosphere (Rudolph, 1982a,b).
