The perfect insects are usually found resting quietly on plants and other objects on the banks of streams. The large brown species, Perla bicaudata, appears in the spring, and is very common in the neighbourhood of pools, streams, and canals.
Tribe IV.—Corrodentia.
This tribe contains two families, one of which is represented in the British Isles.
Family 5, Psocidæ.—This is a family of small insects with simple veined wings. They have a rather large head, and bear a pair of long tapering antennæ. They are found upon trunks of trees, old palings, walls, etc. They are very active in their movements, and generally appear in the imago state about the end of summer or beginning of autumn.
Atropos pulsatorius is one of these. It lives in books and among old damp papers, whence it is often called the "Book Louse."
Fig. 57.—Perla Bicaudata.
Fig. 58.—Psocus Bipunctatus.