THE CLASSIFICATION OF INSECTS 67 



Order VI. — Corrodentia. 



This order comprises a number of small insects which 

 have biting mouth-parts and undergo incomplete meta- 

 morphosis. They were formerly included with the 

 Neuroptera. Two sub-orders are recognised, viz. : — 



Sub-Order 1. — Copeognatha. 



These are small, soft-bodied insects called Psocidce — 

 the only family of the sub-order. Wings are usually 

 present in the adults, the fore-wings being much larger 

 than the hind. Certain species, however, never develop 

 wings, and among these are the familiar " book-lice." 

 One kind, known as Atropos divinatoria, is often 

 numerous in houses, especially if they are damp. It will 

 attack and devour almost any kind of edible substance, 

 including books and papers, while it is sometimes very 

 destructive to collections of dried plants and insects. 

 Many of the winged species are also very common, and 

 may be found upon the trunks and branches of trees, 

 where they feed upon lichens and fungi. They are repre- 

 sented in all parts of the world. 



Sub-Order 2. — Mallophaga. 



These are the small, large-headed insects which are 

 commonly called "bird-lice" or "biting-lice." They are 

 wingless, entirely parasitic, and spend their lives among 

 the plumage of birds or the fur of animals. They feed, 

 however, upon the delicate parts of the feathers and hairs, 

 as well as on the dried secretions of the skin, and must 

 not be confused with members of the order Anoplura 

 (p. 74). Most of the species are associated with birds, 

 though a few are found on mammals. 



