\ 
CHAPTER IX. 
Order CORRODENTIA (Cor-ro-den'ti-a). 
The Psocids (Psocids) and the Book-lice . 
The winged members of this order have four membranous 
wings , with the veins prominent , but with comparatively few 
cress veins; the fore wings are larger than the hind wings; 
and both pairs when not in use are placed roof-like over the 
body , being almost vertical , and not folded in plaits . The 
mouth-parts are formed for biting . The metamorphosis is in¬ 
complete. 
The name of this order is from 
the Latin corrodere , to gnaw, and 
refers to the gnawing habits of these 
insects. 
The wings, especially the fore 
wings, are often smoky in color or 
fig . io 7 .—Psocus vtnosus. variegated. The arrangement of the 
veins of the wings (Fig. 107) differs in a striking manner 
from that of any other biting insect. 
The order includes two families, but representatives of 
only one of them occur in the United States. 
Family PSOCIDS (Psoc'i-dae). 
The Psocids (Pso'cids) and the Book-lice. 
Books may be old and out of date from our standpoint, 
but still be of vital importance to others. Take down from 
the shelf a time-yellowed book and open its neglected leaves 
98 
