ANATOMY OF AN ARTHROPOD. 



91 



wing-covers arc inovably united to the tergum or mesonotum. If 

 we are examining Blatta orientalis we shall not observe these 

 in the female, nor the second pair of wings. The mctathorax 

 bears also a pair of thinner wings, the true organs of Hight. 



The ahdomen (Ah) is flattened dorso-ventrally. It is com- 

 posed of ten distinct somites, the hinder ones being invisible, 

 as they are pushed iirto the anterior ones. The upper parts of 

 the segments are called terga (fig. 35, T). Of the ten, only eight 

 can normally be seen, the eighth and ninth being hidden under 

 the seventh. Situated at the side of the posterior ventral anus 



11 '^ ^f'-^'- 



A. 2. 



Fig. 32. — A, Head, and b, Lower Lip of Cockroach. 



are a pair of small plates called the podieal plates. It is said 

 that these represent an eleventh segment. They can easily be 

 observed by raising the tenth tergum. On the tenth tergum 

 are a pair of jointed processes called cerci (fig. 31, 6'e). In the 

 male a pair of styles are also borne on the ninth sternum (S). 

 The sterna are the ventral plates, the ventral equivalents of the 

 terga. The seventh in the female bears a process passing 

 backwards, forming part of the large genital pouch. 



Appendages of the head. — On the head are placed the an- 

 tennae and the mouth. The latter opens behind the labrum and 

 between the jaws. The two antennae arise from two oval mem- 



