236 THE MECHANICAL FUNCTIONS. 



one is placed upon the under surface of each of the four first 

 joints of the toes, (Fig. 153;) and all the six feet are pro- 

 vided with these suckers. In the Dyiisciis niarginaliSy 

 suckers arc furnished to the feet of the male insect only. 

 The three first joints of the feet of the fore-legs of that in- 

 sect have the form of a shield, the under surface of which is 

 covered with suckers having long tubular necks: there is 

 one of these suckers very large, another of a smaller size, 

 and a great number of others exceedingly small. A few of 

 the latter kind are represented highly magnified in Fig. 154. 

 In the second pair of feet, the corresponding joints are pro- 

 portionally much narrower, and are covered on their under 

 surface with a multitude of very minute suckers. The Jicri- 

 diinn biguttiihivi, wdiich is a species of grasshopper, has 

 one large oval sucker, under the last joint of the foot, im- 

 mediately between the claws. On the under surface of the 

 first joint are three pairs of globular cushions, and another 

 pair under the second joint. Fig. 155 shows these parts. 

 The cushions are filled with an elastic fibrous substance; 

 which, in order to increase the elasticity of the whole struc- 

 ture, is looser in its texture towards the circumference.^ 



The mode in which these suckers operate may be dis- 

 tinctly seen, by observing with a magnifying glass the ac- 

 tions of a large blue-bottle fly in the inside of a glass tum- 

 bler. A fly will, by the application of this apparatus, remain 

 suspended from the ceiling for any length of time without the 

 least exertion; for the weight of the body pulling against 

 the suckers serves but to strengthen their adhesion: hence, 

 we find flies preferring the ceiling to the floor, as a place of 

 rest. 



Insects which, like the gnat, walk much upon the surface 

 of water, have at the ends of their feet a brush of fine hair, 

 the dry points of which appear to repel the fluid, and pre- 

 vent the leg from being wetted. If these brushes be moist- 

 ened with spirit of wine, this apparent repulsion no longer 

 takes place; and the insect immediately sinks and is drowned. 



* Philosophical Transactions for 1S26, p. 324. 



