THE BOOK-LICE AND THEIR ALLIES 



(Order Corrodentia.) 



The curious little wingless insects known as book-lice, 

 which are found frequently in numbers among old, dusty books 

 in damp places, and the interesting little bark-inhabiting creatures 

 known as Psocids are structurally so different from all other 

 insects that they have been brought together in the order Corro- 

 dentia. 



Those which are winged have four wings with prominent 

 veins but very few cross veins. The fore wings are larger than 

 the hind wings, and both are held in a roof-shaped manner over 

 the back when not in use. The mouth-parts are formed for biting, 

 and all of these insects have very incomplete metamorphoses. 



The true Psocidae (I regret that there is no popular name for 

 these insects, for they are very interesting, and always attract 



attention when seen) live to- 

 gether in curious little col- 

 onies on the bark of trees, 

 especially old trees covered 

 with a growth of lichens, or 

 even upon the surface of old 

 fence boards. They possess 

 the power of spinning a cer- 

 tain amount of silk, and each 

 colony is generally covered 

 with a delicate silken web. 

 The eggs are laid together in 

 clusters, and the development 

 of individuals is rather rapid. 

 Psocus venosus is a com- 

 mon form in most parts of the country, and its habits have been 

 described by Hubbard, who has studied it in its southern range 

 upon the trunks of orange trees in Florida. It is small and 



350 



Fig. 240. — Atropos divinatoria. 

 ( Redrawn from Marlatt.) 



