564 



HEMIPTERA-HETEROPTERA 



CHAP. 



very protracted passage are not forthcoming. The develop- 

 ment in Nc'pa, 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 Xepidae are remarkable objects ; 

 that of the common water-scorpion bears seven 

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

 1! nut m is more elongate, and bears only tw T o, 

 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 Hanatra 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- 

 FIG. 277. Egg of ture and formation of the eggs have been 

 (After KorscliVit') investigated with considerable detail by Kor- 

 schelt. L ' 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 



1 //////. S<>r. PlrHiuiiiit. (8) v. 1893, ]>. :"7. There is sonic diversity of opinion 

 as bo the ivspiratory orilices, and some authorities say that thoracic stigmata exist 

 even in I In- inin^'i. 



- Ad, i Ac. German, li. 1887, p. 224, and Zeilschr. wiss. Zoot. xliii. 1886, p. 537. 



