478 THE MICROSCOPE. 



It was formerly supposed, from experiments made by Sir 

 Everard Home, that Flies were enabled to walk against 

 glass, and with the back downwards in various situa- 

 tions, solely by the creation of a vacuum under the 

 soles of their feet, if we may so term, them ; for it was 



observed that the margins of 

 the feet were closely applied 

 to the glass, while the cen- 

 tral part was drawn up. It 

 has, however, been dis- 

 covered that this hypo- 

 thesis was incorrect. Mr. 

 Blackwell (a gentleman re- 

 siding in Manchester, an 

 acute observer of nature,) 

 noticed that Flies remained 

 attached to the sides of an 

 exhausted glass receiver over 



Oan air-pump, even after they 

 had entirely lost the power 

 of locomotion, and that an 

 Fig. 239.-s U ckcr on the leg of a Water- evident distension of the 



beetle. (The circle encloses the object body had been Occasioned 

 about the natural size.) , \ , ,. ,, 



by the exhaustion of the air. 



To detach them from such stations, Mr. Westwood adds, 

 the employment of a small degree of force is found 

 requisite. In prosecuting this subject, clean phials of 

 transparent glass, containing Spiders and various insects in 

 the larva and imago (perfect) states, capable of walking on 

 their upright sides, were breathed into, till the aqueous 

 vapour expelled from the lungs was copiously condensed on 

 the inner surface of the phials. The result was remarkable ; 

 the moisture totally prevented those animals from obtaining 

 any effectual hold on the glass, and the event was equally 

 decisive if a small quantity of oil was substituted for the 

 aqueous vapour. In fact, it was found that powder, or 

 any substance on the inside of the phials, prevented the 

 Flies from climbing; and the idea naturally suggested 

 itself that, some glutinous substance was emitted by the 

 feet of the Flies, which enabled them to adhere to the glass. 

 The next point to be determined, therefore, was, whether 



