564 



HEMIPTERA-HETEROPTERA 



very protracted passage are not forthcoming. The develop- 

 ment in Nepa has been studied to a certain extent. The 

 apical stigmata are the only pair of the abdominal stigmata 

 that exist in the imago of Nepa, the other six pairs being 

 obliterated ; the third, fourth, and fifth, according to Schiodte, in 

 a very peculiar manner : hence, as Martin says, 1 the respiratory 

 system is metapneustic. In an earlier stage of the life, however, 

 these six pairs of stigmata exist in functional activity placed in 

 a groove on the under surface of the body ; so that the condition 

 is that termed peripneustic, and remains so till the final moult, 

 when the long siphon appears. In the early life there is a 

 short prolongation from the end of the body in connection with 

 the pair of grooves alluded to, but it is a single unpaired organ, 

 and does little therefore to explain the appear- 

 ance of the siphon, which must, at present, be 

 considered as being suddenly developed at the 

 last moult. 



The eggs of Nepidae are remarkable objects ; 

 that of the common water-scorpion bears seven 

 filaments at one end (Fig. 277); while that of 

 Ranatra is more elongate, and bears only two, 

 very elongate, threads. These eggs are deposited 

 in the stems of water-plants, being introduced 

 therein, so that the body of the egg is concealed 

 while the threads project : those of Ranatra are 

 placed in stems floating on the water, and in 

 consequence of the threads the stems look as if 

 they were infested by some fungus. The struc- 

 Egg of ture and formation of the eggs have been 

 (After Korscheit) investigated with considerable detail by Kor- 

 schelt. 2 He looks on the filaments as pneu- 

 matic, and considers that they supply a coating of air to the 

 body of the egg; they consist of a spongy mass encircled by two 

 layers of egg-shell, both of these latter being peculiar in struc- 

 ture ; the spongy mass is continuous with a layer of the same 

 kind of substance placed on the interior of the shell of the body 



i'JSutt. Soc. Philomat. (8) v. 1893, p. 57. There is some diversity of opinion 

 as to the respiratory orifices, and some authorities say that thoracic stigmata exist 

 even in the imago. 



2 Ada Ac. German, li. 1887, p. 224, and Zeitschr. wiss. Zool. xliii. 1886, p. 537. 



FIG. 277. 

 Nepa 



