258 



MOTIONS OF INSECTS. 



are without them, they clothe all the tarsi of H. ceneus ( Chal- 

 cites K. Ms.). 1 In two other genera of the same order, Silpha 

 and Cicindela, the anterior tarsi of the males are furnished 

 with them ; in these, therefore, they may be regarded, like the 

 suckers of the larger water-beetles (Dytisci), as given for 

 sexual purposes. 2 The three first joints of the anterior tarsi 

 of many of the larger rove-beetles (Staphylinus L.) are dilated 

 so as to form, as in the last-mentioned insects, an orbicular 

 patella, but covered by cushions. Since in them this is not 

 peculiar to the males, it is probably given that they may be 

 able to support their long bodies when climbing. 



But the most remarkable class of climbers consists of those 

 that are furnished with an apparatus by which they can form 

 a vacuum, so as to adhere to the plane on which they are 

 moving by atmospheric pressure. That flies can walk upon 

 glass placed vertically, and in general against gravity, has long 

 been a source of wonder and inquiry ; and various have been 

 the opinions of scientific men upon the subject. Some ima- 

 gined that the suckers on the feet of these animals were 

 sponges filled with a kind of gluten, by which they were 

 enabled to adhere to such surfaces. This idea, though incor- 

 rect, was not so absurd as at first it may seem ; since we have 

 seen above in many instances, and very lately in that of the 

 Sminthurus fuscus, that insects are often aided in their motions 

 by a secretion of this kind. Hooke appears to have been one 

 of the first who remarked that the suspension of these animals 

 was produced by some mechanical contrivance in their feet. 

 Observing that the claws alone could not effect this purpose, 

 he justly concluded that it must be principally owing to the 

 mechanism of the two palms, pattens, or soles, as he calls the 

 suckers ; these he describes as beset underneath with small 

 bristles or tenters, like the wire teeth of a card for working 

 wool, which having a contrary direction to the claws, and both 

 pulling different ways, if there be any irregularity or yielding 

 in the surface of a body, enable the fly to suspend itself very 



1 The insect here alluded to is figured by Olivier under the name of Tenebrio 

 nitens (No. 57. t. i. f. 4.) : his Helops ceneus (No. 58. t. i. f. 7.) is a different in- 

 sect. 



2 See Kirby, in Fauna Boreali- Americana, on various modifications of these 

 foot cushions amongst some tribes of beetles. 



