194 



HYDROCORIS.E, OR WATER-BUGS. 



FIG. 420. *-NOTO- 



NECTA. 



Bugs, there are two families only. The NOTONECTID/E, or Boat- 

 flies, live almost entirely in the water, where they 

 feed upon other aquatic insects ; these they seize 

 by means of their fore-legs. The legs of the 

 hinder pair have a fringe of bristles along their 

 edge ; by which the surface, with which they 

 strike the water in swimming, is greatly increased. 

 Their general form is extremely well adapted for 

 rapid progression in water ; and it is from the 

 peculiar aspect and movement of the body, that 

 they have received the name of boat-flies or water-boatmen. 

 The insects of this family swim on their backs ; and the arrange- 

 ment of all their organs has reference to this position. When 

 stationary at the surface of the water, as is much their custom in 

 calm hot weather, they very quickly obtain intelligence of the 

 approach of danger, by means of their eyes, which are so placed 

 that they are able to see both above and below the surface ; 

 and then, by a single stroke of their paddles, which are commonly 

 stretched out at full length, they descend out of sight. Their 

 motions are very quick in the element they are chiefly formed to 

 inhabit ; whilst on land they are scarcely able to walk. They 

 can fly well ; but they rarely exercise this power. The larva and 

 pupa only differ from the imago in their 

 smaller size, and in the deficiency of wings. 

 When they descend into the water, the 

 Notonectidae carry down a supply of air for 

 respiration, in a hollow which exists beneath 

 the wings, when these are folded together. 

 The NEPID^E, or Water- Scorpions, receive 

 their name from the scorpion-like form of 

 their fore-legs, which are efficient instruments 

 for seizing their prey. They are in most 

 respects similar in structure and habits to 

 the insects of the preceding family; but 

 their motions are much slower, their legs 

 not being so advantageously formed for 

 swimming. The species represented in the accompanying figure 

 is a very common inhabitant of our ponds. 



FIG. 421. NKPA 



CINKREA. 



