58 



THE STUDY OF INSECTS. 



The subject of external anatomy of insects consists very 

 largely in a study of the sclerites of which the different seg- 

 ments of the body and of its appendages are composed. 

 This part of the subject is quite difficult, and will not be 

 discussed here. It is treated at length in a more advanced 

 text-book by the senior author.* 



Fig. 



-Side-view of Locust with wings 

 removed 



Fig. 71. — Wasp, with 

 head, thorax, and 

 abdomen separated. 



The segments of the body in a fully developed insect are 

 grouped into three regions : head, thorax, and abdomen 

 (Fig. 71). In the larval state this grouping of the segments 

 is not well shown. 



The Head and its Appendages. 



The head is the first of the three regions of the body. 



It is supposed to be formed of several body-segments grown 



together ; but entomologists differ in their views as to the 



number of segments that have entered into its composition. 



The head bears the compound eyes, the simple eyes, the 



antennae, and the mouth-parts. 



The Compound Eyes. — On each side of 

 the head of an adult insect is an organ, 

 which is recognized at once as an eye. 

 But when one of these eyes is examined 

 with a microscope it is found to present 

 an appearance very different from that of 

 the eye of higher animals ; its surface 

 a large number of six-sided divisions 





Fig. 72. — Part of com 

 pound eye, greatly en 

 larged. 



is divided into 



* An Introduction to Entomology by John Henry Comstock 

 by the Comstock Publishing Co., Ithaca, N. Y. 



Published 



