26 



HOW INSECTS ARE CLASSIFIED 



Fig. 23. — Adult 

 Euthrips tritici 

 Original. 



thrips, 

 Fitch. 



Metamorphosis is incomplete. Both 

 nymphs and adults are slender insects, pro- 

 vided with sucking mouth parts. The adults 

 have two pairs of peculiar wings, very nar- 

 row, almost without veins, and fringed along 

 the margins with a row of long hairs, set 

 close together. The wings are laid along 

 the back when not in use. In most species 

 the adults are not more than one tenth or 

 one twelfth of an inch in length. The an- 

 tennae are comparatively short and simple. 



Usually the presence of these insects is 

 recognized fu-st by a whitening of the leaves 

 or a shriveling 

 of other parts on 



which they happen to be feeding. Close 



examination will then reveal the tiny 



active insect itself. 



Hemiptera 



A large group, including the true 

 " bugs," characterized throughout by 

 sucking mouth parts. 



Metamorphosis is incomplete. Active 

 nymphs, which look more or less like the 

 adults except that they have no wings, 

 hatch from the eggs laid by the parent 

 female. 



There are two large subdivisions in 

 this order, the Homoptera and the Het- 

 eroptera, distinguished from each other 

 by the tj^^e of wings, and the manner in 

 which the beak is attached to the head. 



In the Homoptera the wings, four in number, are membranous 

 throughout, and when the insect is at rest, usually are held in a slop- 



FiG. 24. — A cicada. Sub- 

 order Homoptera. Original. 



