OUR COMMON INSECTS. 



INTRODUCTORY. 



WJiat is an Insect? When we remember that the insects 

 alone comprise four-fifths of the animal kingdom, and that 

 there are upwards of 200,000 living species, it would seem a 

 hopeless task to define what an insect is. But a common plan 

 pervades the structure of them all. The bodies of all insects 

 consist of a succession 6f rings, or segments, more or less hai'd- 

 ened by the deposition of a chemical substance called chitine ; 

 these rings are arranged in three groups : the head, the thorax, 

 or middle body, and the abdomen or hind body. In the six- 

 footed insects, such as the bee, moth, beetle or dragon fly, 

 four of these rings unite early in embryonic life to form the 

 head ; the thorax consists of three, as may be readilj- seen on 

 slight examination, and the abdomen is composed either of ten 

 or eleven rings. The body, then, seems divided or insected 

 into three regions, whence the name insect. 



The head is furnished with a pair of antennas, a pair of jaws 

 (mandibles), and two pairs of maxilla, the second and basal 

 pair being united at their base to form the so-called labium, or 

 under lip. These four pairs of appendages represent the four 

 rings of the head, to which they are appended in the order stated 

 above. 



A pair of legs is appended to each of the three rings of the 

 thorax ; while the first and second rings each usually carry a 

 pair of wings. 



