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 heUnd with a long 

 slender siphon; front legs more or less elongate for capturing 

 prey, placed quite at the front 

 edge of the prothorax. — This 

 family consists of two interest- 

 ing but very dissimilar genera, 

 Mpa and Ranatra. Both are 

 widely distributed over the 

 earth, and are rather numerous 

 in species.^ We have one 

 species of each genus in Britain. 

 Nepa 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. 

 Eanatra 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 Fig- 276— Ranatra linearis, with the two 

 T j_ 1 1 portions, a, of the respiratory siphcii 



processes are elongated pleurae, separated. 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 



^ Ferrari, Monograph of iVepa, An7i. Rofmus. Wien, iii. 1888, p. 171. 



