8 THE INSECT WORLD. 
in different ways. Some move their six legs successively, or only 
two or three at a time without distinction, but never both legs of 
the same pair together, consequently 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 very regularly. 
They commence by moving the posterior 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 im 
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 downward 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. 
Swimming differs essentially from walking, for the foot being 
surrounded by a resisting medium, the legs on both sides are 
moved at the same time. . 
The act of jumping is principally performed by the hind legs. 
Insects which jump have these legs very largely developed, as in 
the figure (fig. 9). When about 
to jump they bring the tibia into 
contact with the thigh, which is 
often furnished with a groove to 
receive it, having on each side a 
row of spines. The leg then sud- 
denly straightens like a spring, 
and the foot being placed firmly 
on the ground, sends the insect 
into the air and at the same time 
propels forward. The jump is greater in proportion as the leg is 
longer. 

Fig. 9.—Posterior leg of a jumping insect. 
To speak here in a general manner of the wings of insects 
would be too’ vague. We shall speak of them at length in their 
