INSECT A . RHY'NCOTA 



281 



holds on to the weeds by the short first pair of legs, and the 

 hind legs lie stretched out at full length on each side. It is 

 a swift swimmer, and will catch animals larger than itself, 

 diving underneath its victim and catching hold of it with its 

 front legs, and then burying its powerful beak in the flesh 

 and sucking from it all its juices. The eggs are laid singly 

 in the tissues of water-weeds. The larvae (Fig. 206, A) are 

 in shape and habits much like the adults, but are of a pale- 

 green colour with red eyes ; also they have at first no wings, 

 though these develop gradually. 



Corixa. 



The closely allied, but much smaller, Corixa 

 uses its back legs in swimming, 

 much as Notoneda does, but 

 swims with its back uppermost ; 

 also the back is flat instead of 

 being strongly keeled, and the 

 " scutellum " is not distinct as it 

 is in the Boatman. The body, 

 which is about half an inch long, 

 is heavier than the water, and 

 therefore Corixa has to swim to 

 the surface to breathe, instead 

 of merely floating up. At the 

 surface, the thorax projects out 

 of water, and air is taken in 

 directly by the thoracic spiracles, 

 a new air-film forming round the 

 neck. 



The commonest species is 

 Corixa geoffroyi, which is dark 

 brown in colour, and spotted 

 with yellow on the thorax and 

 upper wings. The eggs are fixed 

 to submerged objects, and the larvae are similar to the adults 

 except for their lack of wings. Corixa, like Notonecta and 

 Nepa, spends the winter buried in the mud at the bottom 

 of the water, but a warm day will always entice it out for a 

 swim and a feed. 



Corixa geoffroyi. 



The adult insect above and the larva 

 below. (Natural size shown by 

 the lines to the right.) 



