132 ELEMENTARY LESSONS ON INSECTS 



These are common on lichen-covered bark of trees and on 

 boards of fences. A minute pale, wingless species, commonly 

 found between the leaves of old books, is known as the 

 "book louse." 



For further information concerning all of these, consult 

 the larger works on entomology. 



There remain three orders containing a few insects of 

 larger size and more importance. 



Isoptera, termites or "white ants"; soft-bodied, mostly 

 pale insects with biting mouthpa r ts and incomplete meta- 

 morphosis. The wings 

 when present are two 

 pairs that are alike, as 

 the name implies,* with 

 a few stiff veins at the 

 front and a broad irreg- 

 ular meshwork of faded- 

 out venation behind. 

 Termites are social in 

 habits are differentiated 

 into castes. 

 These are wood-eating 

 insects of great importance in the warmer parts of the earth, 

 where they destroy books, furniture and even houses. They 

 live in colonies like ants, but are quite unlike ants in every 

 other way. 



Fig. 54. — The onion thrips, Thrips tabaci, a minute 

 sucking insect of much economic importance. 



* Isos, equal and pteron, wing. 



