THE WATER-BOATMAN. 13 



And it is worthy of notice, that the greater the improvement in 

 rowing, the nearer do we approach the original insect model. 



The first which we shall notice is the insect which, from its 

 singular resemblance to a boat propelled by a pair of oars, has 

 received the popular name of Water-boatman. Its scientific 

 name is Notonecta glanca, the meaning of which we shall 

 presently see. It belongs to the order of Heteroptera, and is 

 one of a numerous group, all bearing some resemblance to each 

 other in form, and being almost identical in habits. Though 

 they can fly well, and walk tolerably, they pass the greater 

 part of their existence in the water, in which element they 

 find their food. 



Predacious to a high degree, and armed with powerful weapons 

 of offence, it is one of the pirates of the fresh water, and may be 

 found in almost every pond and stream, plying its deadly vocation. 



Its large and powerful wings seem only to be employed in 

 carrying it from one piece of water to another, while its first 

 and second pairs of legs are hardly ever used at all for progres- 

 sion. The last pair of legs are of very great length, and 

 furnished at their tips with a curiously constructed fringe of 

 stiff hairs. The body is shaped in a manner that greatly 

 resembles a boat turned upside down, the edge of the elytra 

 forming a sort of ridge very much like the keel of the boat. 



When the creature is engaged in swimming, it turns itself 

 on its back, so as to bring the keel downwards, and to be able 

 to cut the water with the sharp edge. From this habit it has 

 derived the name of Notonecta, which signifies an animal 

 which swims on its back. The first and second pairs of legs are 

 clasped to the body, and the last pair are stretched out as 

 shown in the illustration, not only looking like oars, but being 

 actually used as oars. 



Now, I wish especially to call the reader's attention to the 

 curiously exact parallel between the water-boatman and the 

 human oarsman. As the reader may probably know, the oar 

 is a lever of the second order, i.e. the power comes first, then 

 the weight, and then the fulcrum. The arm of the rower 

 furnishes the power, the boat is the weight to be moved, and 

 the water is the fulcrum against which the lever acts. 



I have more than once heard objections to this definition, 

 the objectors saying that the water was a yielding substance, 



