CHAPTER III 



STRUCTURE AND DEVELOPMENT OF INSECTS 

 THE more experience the farmer has with insect pests, the 

 more he comes to realize that if he would successfully combat 

 them he must have a certain amount of knowledge concerning 

 their structure and growth. 



In general, the artificial means which may be effectually 

 used to combat an insect pest will depend more or less upon 

 the anatomical structure of the insect, while control by general 

 methods of culture will depend upon a knowledge of the peculiari- 

 ties of its life-history. The value of a proper understanding of 

 these important factors in insect control is therefore apparent. 



General Structure of an Insect 



The body of an insect is composed of three separate parts 

 the head, thorax, and abdomen (Fig. 14), each of which is com- 

 posed of several rings or segments. 

 To the head are attached the 

 jointed antennae, or feelers, the 

 compound eyes, and the mouth- 

 parts, which are described below. 

 Each of the three segments of 

 the thorax bears a pair of legs, 

 and adult insects usually possess 

 one or two pairs of wings upon 

 the last two segments of the 

 thorax. The abdomen is com- 



^ 1 . T,. , ,. posed of nine or ten segments, 



FIG. 14. Honey-bee, showing the f 



three principal regions of the body but bears no appendages save 

 of an insect: h, head; th, thorax; the ovipositor of the females of 

 aba. abdomen. . . , 



certain orders. 



Harvest-mites, or " daddy-long-legs," sow-bugs, thousand- 

 legged worms, and related forms are often popularly called 



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