INSECTS 



107 



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. 50. — 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 



