390 INSECT TRANSFORMATIONS. 



mentions "a very small handsome lizard, about a 

 finger's length, which climbs along the walls, and 

 even along glass, in pursuit of flies and other in- 

 sects ;"* and Sir Joseph Banks noticed another lizard, 

 named the gecko {Lacerta Gecko^ Linn.) which 

 could walk against gravity, and which made him de- 

 sirous of havmg the subject thoroughly investigated. 

 On mentioning it to Sir Everard Home, he and Mr. 

 Bauer commenced a series of researches, by which 

 they proved incontrovertibly, that in climbing upon 

 glass, and walking along the ceilings with the back 

 downwards, a vacuum is produced by a particular 

 apparatus in the feet, sufficient to cause atmospheric 

 pressure upon their exterior surface. 



The apparatus in the feet of the fly consists of two 

 or three membranous suckers connected with the last 

 joint of the foot by a narrow neck, of a funnel shape, 

 immediately under the base of each claw, and move- 

 able in all directions. These suckers are convex 

 above and hollow below the edges, being margined 

 with minute serratures, and the hollow portion 

 covered with down. In order to produce the vacuum 

 and the pressure, these membranes are separated and 

 expanded, and when the fly is about to lift its foot, 

 it brings them together, and folds them up as it were 

 between the two claws. By means of a common 

 microscope, these interesting movements may be 

 observed when a fly is confined in a wine-glass. t 



It is a very remarkable analogy, that many flying 

 insects, as well as many birds, instead of walking, 

 leap or hop along somewhat in the manner of a 

 kangaroo or a jerboa. But the most common and 

 best known instance of a leaping insect, is the flea 

 {Pulei irritans)^ whose wings are, according to 

 Kirby, obsolescent. The structure of this annoying 



* Voyage to the Isle of France, p. 73. 

 t Philosopli. Trans, for ISIH, p. 325. 



