516 HEMIPTERA. 



foul odorous fluid. Lacaze-Duthiers has given a sectional view 

 of Ranatra (Fig. 516 ; v, dorsal vessel ; i, intestine ; N, ner- 

 vous cord) which shows the relation of the elements of an 

 abdominal segment. T, is the tergum ; EM, the epimerum ; 

 ES, the episternum, and s, the sternum. 



The ovipositor and the genital armature are generally con- 

 cealed within the tip of the abdomen, being rarely exserted so 

 as to form a prominent part of the body. It differs greatly in 

 its development, and is difficult to reduce to a common, type. 

 Lacaze-Duthiers states that we may consider the abdomen of 

 the Hemiptera as consisting of ten or eleven segments, accord- 

 ing as we consider the horny ring, lying between the abdomen 

 and thorax as the basal ring of the abdomen, or not. He re- 

 gards the former view as the true one. This author contends 

 that in Ploa the tergum of the first and second abdominal 

 v segments (proto and dentotergites) are coal- 

 < esced, and that the original sutures are marked 

 by simple striae, while at the opposite end of 

 the abdomen the genital and anal outlets are 

 separated by three rings, i.e., the eighth, 

 ninth and tenth. 



In the Cicadidce and Phytocoris the ovipositor is per- 

 fect and much as described in the Hymenoptera. In the 

 Fulgoridce, Naucoris, Ploa and Notonecta, the eighth 

 segment is complete, while the ovipositor is more or less in- 

 complete, and it often happens that a reunion of secondary 

 pieces represents a principal piece, and that the elements of 

 the two postgenital rings are articulated together by overlap- 

 ping each other. 



In Ranatra, Nepa and Gerris is a third modification of the 

 ovipositor, where the postgenital segment is incomplete, and 

 the sternal appendages and sternum of the segment bearing 

 the ovipositor only remain, the other parts being aborted. In 

 the Pentatomids and Cimex there is no ovipositor, but the 

 aborted elements are more or less developed, so as to be 

 identifiable. 



The nervous system consists, besides those of the head, of 

 two thoracic ganglia, of which the anterior is the smaller, which 

 send off two main trunks to the abdomen. 



