VIII 



CRYPTOCERATA NEPIDAE 



563 



in South Europe. The other members of the family are very 

 widely scattered over the surface of the earth. 



Fam. 21. Nepidae. Abdomen furnished lu-li'md with a lony 

 slender siphon; front legs more or less elongate for capturiinj 

 pri't/, i>l <<<! ij/'/fe at the front 

 f</<fi- of the prothorax. This 

 family consists of two interest- 

 ing but very dissimilar genera, 

 Nepa and Ranatra. Both are 

 widely distributed over the 

 earth, and are rather numerous 

 in species. 1 We have one 

 species of each genus in Britain. 

 Xrjia cinerea, the common 

 " water - scorpion," is one of 

 the commonest of Insects in 

 Southern Britain, living con- 

 cealed in shallow waters when 

 nearly or quite stagnant. 

 Ranatra linearis (Fig. 276) is 

 much less common, and appears 

 to be getting rarer ; it is not re- 

 corded from farther north than 

 Cambridge. 



The nature of the respir- 

 atory arrangements in these 

 Insects is of considerable in- 

 terest ; the long tube at the 

 extremity of the body consists 

 of two parts (as shown in Fig. 

 276) brought together in the 

 middle, one from each side. 



Lacaze-Duthiers states that the Fir,. 276 Emmim linearis, with the two 



n , portions, a, of the respiratory siphon 



processes are elongated pleurae, ,,., i;ll , a ted. Cambridge. 



but in the young it is far 



from clear that this is the case. However that may be, they 

 seem to convey air to the true breathing organs, situate inside 

 the cleft on the apical part of the abdomen itself; but details 

 as to the way in which transfer of air is effected along this 

 1 Ferrari, Monograph of Nepa, Ann. Jl/ifmus. U'tcn, iii. 1888, p. 171. 



