MICROSCOPE IN- DOORS. 67 



common bee (Fig. 199, PI. 7). The feet are also 

 covered with hairs, and are frequently supplied with 

 hooked joints, which assist the animals in laying 

 liold of rough objects where their suckers would be 

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

 the hooked joints and hairs enable the creature to 

 crawl with facility (Fig. 200, PL 7). In the Dyticus, 

 the fore leg is supplied with two large suckers (Fig. 

 209, #, PL 8), besides a number of smaller ones, and a 

 hook ; whilst the foot of the middle leg is destitute 

 of the large suckers (6). 



The legs of beetles are often covered with little 

 cushion- like bodies, which undoubtedly act as suck- 

 ers (Fig. 214, PL 8). 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) (Fig. 208, PL 8),.in which the first 

 leg (a) is very much elongated, whilst the third is 

 broad and short (c), and adapted for swimming, from 

 its oar-like form. The second leg (b) 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 (Fig. 213, 

 PL 8) ; when it will be found to consist, at its 

 extremity, of a little sac surmounted with hooks. 



The wings of insects, too, are beautiful objects ; 

 easily investigated by a low power. The nerves 

 which run through them are supplied with trachea, 

 and they thus become organs of respiration. The 

 under wing of the bee is supplied with a series of 

 hooks (Fig. 204, PL 7), which slide on a thickened 

 nerve on the upper wing (a), and keep the wings 

 steady during flight. 



The lepidopterous insects, including the butterflies 

 and moths, have got their name from the scales on 



