564 



HEMIPTERA-HETEROPTERA 



CHAP. 



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- 

 FIQ. 277. Egg of ture and formation of the e<ws have been 





(After Korscheit.) investigated with considerable detail by Kur- 

 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 



1 Lull. 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. 



z Ada Ac. German, li. 1887, p. 224, and Zcitschr. wiss. Zool. xliii. 1886, p. 537. 



