238 TEESH-WATEE AQTJAEIA. 



Gravesend. They are all more or less interesting in the 

 aquarium, where they may be kept much more easily than 

 the NotonectcB. The head of a Corixa is rather curious; it 

 is convex in front, and very concave behind, and it is attached 

 apparently so slightly to the thorax that there always seems 

 a danger of the creature becoming decapitated. Indeed, I 

 have not seldom found Corixos in the aquariiim floating about 

 dead and minus their heads. The creatures take in a fresh 

 supply of air by coming up to the surface of the water in 

 such a way that the top of their heads and the upper part 

 of their thoraces are slightly out of the water, and then, 

 bending their heads downwards and upwards, they enclose 

 some air, which is conducted to the breathing-holes beneath 

 their bodies. During summer the bottoms of shallow ponds 

 may be seen literally swarming with small species of Corixa, 

 which are continually coming to the surface of the water for 

 oxygen. Corixce have wings, which they frequently use. 

 The upper part of their bodies is flat, and in many of the 

 species is ridged. While in the aquarium Corixce are much 

 more easUy provided with food than the Notonectce, for they 

 will readily content themselves with garden-worms or pieces 

 of raw meat. They are very good scavengers. I have kept 

 a great many Corixce for a long time, and I have never seen 

 them attack fish, but I am not sure that they would not do so 

 if starved. They will occasionally prey upon each other. The 

 Corixce make quite a distinct noise as they knock their heads 

 against the side of the aquarium in which they are confined. 

 Corixa Geoffroyi (Fig. 150) is the largest and about the 



commonest species of the 

 CorixcB. It is about |in. long, 

 and the upper part of its 

 body is a kind of dark brown, 

 minutely spotted with yellow, 

 with the exception of the 

 Fig. 150. Corixa Geoffroyi. thorax, which is marked with 



trajisverse black and yellow 

 lines. These spots and lines cannot well be seen without 

 the help of a magnifying-glass. The legs are also yellow, 



