MUS. COATES'S BATH. 65 



seized and borne below, held firmly in the jaws of its 

 captor. 



It is an insect full of wonders, and contains in itself 

 the elements of more than one mechanical invention. 

 In the first place it is a living diving-bell. Like all 

 insects it breathes atmospheric air by means of tubes, 

 which permeate the whole of the body. The apertures 

 by which these tubes communicate with the air lie 

 on the upper part of each side, under the wing-cases. 

 Now these wing-cases, or elytra, are convex, while the 

 upper part of the body is flat, so that there is a space 

 between the wing-cases and the body. Every now and 

 then the beetle comes to the surface of the water, pro- 

 trudes the end of the body, draws in a supply of air 

 into the space between the elytra and the body, and 

 dives again, the elytra fitting so closely to each other 

 and to the sides that the air cannot escape. Some- 

 times, if the beetle be not alarmed, it will remain at 

 the surface, with its head downwards, and its body 

 balanced by its extended swimming-legs, and on a calm 

 day quite a number of water-beetles may be seen thus 

 suspended. 



The swimming-legs which have just been men- 

 tioned are themselves very wonderful examples of 

 structure. They are so made that the only movements 

 which they can perform are those of swimming, and 

 they are fringed with stiff hairs so set that when the 

 leg is struck against the water the hairs stand out and 

 act like the blade of an oar ; while, when the limb is 



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