INSECTS 



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INSECTS. 



The insects are divided into three groups: (1) the biting 

 or chewing insects, (2) the boring insects, (3) the sucking 

 insects. 



In order to understand insect injury, the reader must first 

 know the various stages, of the life history through which 

 insects pass. The changes in the life of an insect are known 

 as metamorphosis. Complete and incomplete metamor- 

 phosis are recognized in the life of the different insects. 



Fig. 51. — Showing the successive stages of the squash bug which is the 

 incomplete metamorphosis. (Folsom.) 



Complete metamorphosis means that the insect passes 

 through four complete changes during its life. Beginning 

 with the adult, we arrange the stages in the life history 

 in the following order: (1) the egg stage, (2) the larva stage, 

 (3) the pupa stage, (4) the adult stage. The adult lays the 

 egg from which hatches the little worm or the larva. The 

 worm eats the plant upon which it is placed, continues to 

 grow larger and to consume more of the plant tissue until 

 it finally reaches its full growth. When this feeding period 

 is finished, the worm goes into a quiescent stage, and this 

 stage is called the pupa. During the pupa stage the insect 

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