232 



AN INTRODUCTION TO ENTOMOLOGY 



Fig. 239. — Caudal segments of a 

 nymph of a female locust, dorsal 

 aspect: //, eleventh abdominal 

 segment; /, telson; c, cercus. 



known as the podical plates; but they have recently been named 

 the paraprocis because they are situated one on each side of the 



anus. They are the sternum of the 

 eleventh abdominal seji^ment, which 

 is divided on the midventral line, to 

 admit of the expansion of the poste- 

 rior end of the alimentar}^ canal during 

 defecation. 



In this insect the cerci (Fig. 238, c) 

 project from beneath the caudal border 

 of the tenth tergiim ; they appear, there- 

 fore, to be appendages of the tenth ab- 

 dominal segment; but it is believed 

 that in all insects where cerci are pres- 

 ent they are appendages ■ of the elev- 

 enth abdominal segment. This, for 

 example, is obviously the case in the 

 Plecoptera (Fig. 240). The homology 

 of the paraprocts is also well shown in 

 this figure. 



The ovipositor consists of three 

 pairs of processes or gonapophyses; 

 these are termed the valves or valvules of the ovipositor; they are dis- 

 tinguished as the dorsal, ventral, and inner valvulae, respectively. 

 In the locust the dorsal valvulee (Fig. 238, d) and the ventral valvulas 

 (Fig. 238, v) are strong, curved, and pointed pieces; the inner valvu- 

 las (Fig. 238, i) are much smaller. 



The relation of the gonapophyses to the segments of the abdomen 

 can be seen more clearly in the female of Ceuthophilus (Fig. 241). 

 The ventral valvulae arise from the posterior margin of the eighth 

 stemirm and the dorsal and inner valvulae arise from the ninth 

 stermmi. These relations can be seen even more clearly in very young 

 nymphs where the rudiments of the gonapophyses are mere tubercles, 

 one pair on the hind margin of the 

 eighth abdominal sternum and two 

 pairs on the ninth sterntun (Fig. 

 242). 



In the male, as in the female, 

 the form of the caudal end of the 

 abdomen and its appendages dif- 

 fers greatly in different members of 

 this order. Space can be taken here 

 to illustrate these parts in only a 

 single species. For detailed ac- 

 counts of these parts in other mem- 

 bers of this order, special papers on 

 this subject should be consulted. 

 Among the more recent and gen- 

 erally available of these are those of 



Fig. 240. — End of abdomen of Pter- 

 onarcys dorsata, female, ventral 

 view: 77, 77, the divided sternum 

 of the eleventh abdominal segment, 

 the podical plates ; c, c, basal parts 

 of the cerci. 



