INTRODUCTION. 



Wc shall not dwell on the different parts, as they perform functions 

 which will occupy us later, when speaking of the various species of 

 the great class of insects. 



The functions which the legs 

 of insects have to perform con- 

 sist in walking, swimming, or 

 jumping. 



In walking, says M. Lacor 

 daire, insects move their legs in 

 different ways. Some move their 

 six legs successively, or only two 

 or three at a time without dis- 

 tinction, but never both legs of 

 the same pair together, conse- 

 quently one step is not the same 

 as another. The walk of insects 

 is sometimes very irregular, espe- 

 cially when the legs are long ; and 

 they often hop rather than walk. 

 Others 'have one kind of step, 

 and walk ver}^ regularly. They 

 commence by moving the pos- 

 terior and anterior legs on the 

 same side and the intermediate 

 ones on the opposite side. The 

 first step made, these legs are 

 put down, and the others raised 

 in their turn to make a second. 



Running does not change the 

 order of the movements, it only 

 makes them quicker — very rapid 

 in some species, and surpassing 

 in proportion that of all other 

 animals ; but in others the pace 

 is slow. Some insects rather 

 crawl than walk. 



In swimming, the posterior legs play the principal part. The 

 other legs striking the water upwards or downwards, produce an 

 upward or do\^Tlward motion. The animal changes its course at 

 will by using the legs on one side only, in the same way as one 

 turns a rowing boat with one oar without the aid of a rudder. Swim- 

 ming differs essentially from walking, for the foot being surrounded 



Fig. o. — Poiterior leg of a jumping insect. 



