232 



AN INTRODUCTION TO ENTOMOLOGY 



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

 the para prods because they are situated one on each side of the 

 anus. They are the sternum of the 

 eleventh abdominal segment, which 

 is divided on the midventral line, to 

 admit of the expansion of the poste- 

 rior end of the alimentan,' canal during 

 defecation. 



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

 project from beneath the caudal border 

 of the tenth tergum ; 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 

 Fig. 239.-Caudal segments of a o^ the paraprocts IS also well shown in 

 nymph of a female locust, dorsal this figure. 



aspect: 11, eleventh abdominal 'phg ovipositor consists of three 



segment; /, telson; r, cercus. ^^^-^^ ^^ processes or gonapophyses ; 

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

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

 In the locust the dorsal valvulae (Fig. 238, <i) and the ventral valvulce 

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

 lae (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 

 stemimi and the dorsal and inner valvulce arise from the ninth 

 sternum. 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 stemiun and two 

 pairs on the ninth sternum (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- Fig. 240.— End of abdomen of Pier- 

 bers of this order, special papers on onarcys dorsata, female, ventral 



this subject should be consulted. ""f^T- V- ^'l^^^t/''^^^^^ ^tevnnm 



, .1 ,1 of the eleventh abdominal segment. 



Among the more recent and gen- the podical plates; c, c, basal parts 



erally available of these are those of of the cerci. 



