ANATOMY AND EMBRYOLOGY. 257 



that at the time were proving such a plague in parts of Kansas and 

 Missouri. In February, 1876, the wheat and oats fields in parts of Texas 

 were being badly damaged by small insects that were similarly supposed 

 to be young locusts, but which, in reality, were also leaf-hoppers; two 

 species, more particularly the I^iedrocejihalajiavice^halaj Fitch, and a Jas- 

 sus allied to immicus, Say, being concerned. 



CHAPTER IX. 



ANATOMY AND EMBEYOLOGY. 



In order to properly understand the habits and physiology of the lo- 

 cust, in connection especially with its great voracity, powers of flight, 

 and the injury it receives from its internal and external parasites — 

 questions of so much importance in studying its natural history and re- 

 lations to agriculture — it has been thought that a brief general account 

 of its external and internal anatomy, as well as the minute anatomy of 

 the digestive system, would be of considerable practical value. 



EXTERNAL ANATOMY. 



On making a superficial examination of the locust, any one will soon 

 perceive that its body consists of an external crust, or thick, hard in- 

 tegument, protecting the soft parts or viscera within. This integument 

 will be seen to be at intervals segmented or jointed, the segments more 

 or less like rings, which in turn are subdivided into pieces. These seg- 

 ments or rings are most simple and easily comprehended in the abdomen 

 or hind bjpdy, which is composed of 10 of them. The body is composed 

 of 17 of these segments, variously modified and more or less imperfect 

 and difficult to make out, especially at each extremity of the body, namely,, 

 in the head and at the end of the abdomen. These 17 segments, more- 

 over, are grouped into 3 regions, 4 composing the head, 3 the thorax, 

 and 10 the hind body, or abdomen. On examining the abdomen, it will 

 be found that the rings are quite perfect, and that each segment may 

 be divided into an upper (tergal), a lateral (pleural), and an under (ster- 

 nal) portion, or arc (Fig. 12, A). These parts are respectively called 

 iergite, pJeurite, and sternite, while the upper region of the body is called 

 the tergum, the lateral the pleurum, and the ventral or under portion 

 the sternum. 



As these parts are less complicated in the abdomen, we will first de- 

 scribe this region of the body, and then describe the more complex thorax 

 and head. The abdomen is a little over half as long as the body, the 

 tergum extending far down on the side and merging into the pleurura 

 without any suture or seam. The pleurum is indicated by the row of 

 spiracles, which will be noticed further on. The sternum forms tbe 

 17 a 



