EXTERNAL ANATOMY. 63 



is immovably united to the tenth, a faintly marked suture 

 separating the two. On the median line the tenth tergum 

 is very narrow, but at the sides it is about as long as the 

 ninth. The posterior margin of the tenth is sharply defined. 

 The eleventh tergum is a movable shield-shaped plate upon 

 the median dorsal surface. It is about as long as the eighth 

 tergum, and it is divided into two nearly equal portions by 

 a faint transverse suture. In shape it is quite different from 

 the other terga, and its sides as well as its posterior margin, 

 are free. On each side of this plate the outline of the dorsal 

 surface of the body is completed by a setose movable plate, 

 about as large as the eleventh tergum, the cerciis, (cer). This 

 plate projects back from the lateral margin of the tenth 

 tergum, to which it is movably articulated. Projecting be- 

 vond the end of the eleventh tergum the end of the ventral 

 sub-genital plate is visible. If the end of the eleventh tergum 

 is raised, a pair of vertical plates can be seen on each side of 

 the median line, the podical plates. Between these plates is 

 the anus, and below them the genital chamber, already 

 noticed. 



In a side view, (.4), the sterna of the second to eighth seg- 

 ments are equal in length to the corresponding terga, and 

 the constrictions between the segments entirely surround 

 the body. The suture, which on the dorsal surface marks 

 the line between the ninth and tenth terga, does not extend 

 downwards, and the lower margins of these two terga 

 form a single plate. Below this plate is the ninth sternum, 

 as long as the area formed b\' the union of the ninth and 

 tenth terga. Running backwards from the posterior margin 

 of the tenth tergum is the flat cercus. Above this a portion 

 of the eleventh tergum is visible. Below and internal to the 

 cercus is the podical plate, triangular in a side view, and be- 

 low this the large sub-genital plate, wdiich is joined to the 

 ninth sternum. 



The abdomen of the female, (Fig. 39), in a ventral view, 

 ( C),has the first to the seventh sterna like those of the male. 



