242 



INSECT A. 



observers. The foot of the house-fly, nevertheless, is a very curious 

 piece of mechanism ; for, in addition to the recurved hooks pos- 

 sessed by other climbing species, it is furnished with a pair of 

 minute membranous flaps (Jig. 107, c), which, under a good mi- 

 croscope, are seen to be covered with innumerable hairs of the ut- 

 most delicacy : these flaps, or suckers as they might be termed, 

 adhere to any plane surface with sufficient tenacity to support the 

 whole weight of the fly, and thus confer upon it a power of pro- 

 gression denied to insects of ordinary construction. 



Fig. 107. 



In Bibio febrilis (fig. 107, B) the sucking discs appended to 

 the foot are three in number, but in other respects their conforma- 

 tion is the same. 



In Cymbex lutea (fig. 107, D) the arrangement of the suckers 

 is different, one large and spoon-shaped disc being attached to the 

 extremity of each tarsal joint. Moreover, in this case there is 

 another singular structure, two spur-like organs project from each 

 side of the extremity of the tibia, each being is provided with 

 a sucking disc, while the two together form a strong prehensile 

 forceps. 



In some water-beetles (Dytiscidce) the feet are armed with a 

 still more elaborately constructed apparatus of suckers ; but in this 

 case, as they are only met with in the male insect, they perhaps 

 ought rather to be looked upon as a provision made for the purpose 



