MICROSCOPE IK-DOORS. 89 



to the locomotive habits of the insect. In the 

 common fly it is terminated with a pair of disks, 

 which are covered with suckers, called pulvilli. 

 Those of the Empis, a species of fly, are drawn at 

 figure 205, plate 7. By means of these suckers the 

 animal is enabled to lay hold of smooth surfaces, and 

 thus to crawl up them. They also exude a glutinous 

 matter, which assists in this process. The same 

 kind of arrangement is observed in the common 

 bee, represented in figure 20G. The feet are also 

 covered with hairs, and are frequently suppMcd with 

 hooked joints, which assist the animals in laying 

 hold of rough objects where their suckers would be 

 of no use. In the spicier there are no suckers, but 

 the hooked joints and hairs enable the creature to 

 crawl with facility. These hooks are seen in the 

 foot of the spider in figure 207, plate 7. In the 

 Dyticus the fore leg is supplied with two large 

 suckers, which are seen in figure 218, plate 8, 

 besides a number of smaller ones, and a hook ; 

 whilst the foot of the middle leg is destitute of the 

 largo suckers, as seen at figure 219. 



The legs of beetles are often covered with little 

 cushion-like bodies, which undoubtedly act as 

 suckers. These are seen at figures 215, 216, 217. 

 The three legs often differ very much from each other, 

 and probably perform modified functions, according 

 to their structure. This is well seen in the legs of 

 the whirligig-beetle (Gyrinus natator\ in which the 

 first leg, in figure 215, is very much elongated, 

 whilst the third is broad and short, as at figure 217. 

 and adapted for swimming, from its oar-like form. 

 The second leg, seen at figure 216, is intermediate 

 in form and size. 



As a contrast to these legs, adapted for the 

 varied functions of the perfect insect, the leg of 

 any common caterpillar may be examined ; when it 



