232 FRESH-WATEB AQTIAEIA. 



The two familes belonging to the tribe EydroeoriscB (Water- 

 Bugs) found in Britain are the NepidcB and the Notonectidw. 

 The former include the genera Nepa, Banatra, and Naucoris, 

 and the latter Notonecta and Corixa. 



All the members of the Nepidce family (Water-scorpions) live 

 for the greater part of their life in the water, and there feed 

 upon other aquatic animals. They are not very active insects, 

 trusting rather to stealth than to speed for the capture of 

 their victims. The Water- scorpions have very powerful rap- 

 torial fore-legs, with which they seize and hold their prey 

 while they extract all its juices. There are four other legs, 

 which are chiefly used for swimming or crawling among 

 aquatic plants. Their rostrum, which has three joints, is 

 quite strong enough to pierce the human skin. They have 

 wings and fair powers of flight. 



The Water-scoi-pion should not be kept in the same 

 aquarium with small fish, for it will kill them ; nor with large 

 ones, for they might kill it. Though this insect is so coura- 

 geous and predaceous, it will quickly succumb to improper 

 treatment. It is an interesting object in a small tank, where 

 it ought to be the only occupant. The vessel in which it is 

 confined should be covered, and should also be provided with 

 something or other, such as a piece of cork, wood, or pumice- 

 stone, which will float, and upon which the creature can climb 

 when it wishes to leave the water for a short time. With 

 care the Water-scorpion will live for a long while in captivity. 

 For food it apparently prefers small fish and tadpoles, but it 

 is content with almost anything of an animal nature. 



Nepa cinerea (Fig. 146) is very common in ponds nearly 

 everywhere. It readily escapes detection, however, owing to 

 its colouring, which is similar to that of the mud upon which 

 it is fond of resting. More than once I have thought that 

 my Water-scorpions had escaped from their aquarium, on 

 account of this facility of hiding, and only discovered my 

 mistake by their change of position. This aptitude for con- 

 cealment is very useful to the insect, for its prey comes un- 

 suspectingly into its neighbourhood, and only realises its danger 

 as it is seized by the cruel fore-legs, and pulled within reach 



