300 



INSECTA. 



The structure of the foot is therefore modified : the tarsus in this insect 

 terminates in a single moveable claw, which bends back upon a tooth- 

 like process derived from the tibia, and thus forms a pair of forceps, 

 fitted to grasp the stem of the hair and secure a firm hold. 



(782.) Many insects, especially those of the Dipterous order, are able 

 to ascend the smoothest perpendicular planes, or even to run with 

 facility, suspended by their feet, in an inverted position, along substances 

 which, from their polished surfaces, could afford no hold to any appa- 

 ratus of forceps or hooklets. In the common flies (Muscidce), the exer- 

 cise of this faculty is of such everyday occurrence, that, wonderful as it 

 is, it scarcely attracts the attention of ordinary observers. The foot of 

 the House-fly, nevertheless, is a very curious piece of mechanism ; for, 

 in addition to the recurved hooks possessed by other climbing species, it 

 is furnished with a pair of minute membranous flaps (fig. 150, c), which, 



Fig. 150. 



Feet of insects : A, F, Dytiscus. B, Bibiofebrilis. c, Musca domestica. r, Cimbex lutea. 

 E, Abyssinian Grasshopper. 



under a good microscope, are seen to be covered with innumerable hairs 

 of the utmost 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 progression denied 

 to insects of ordinary construction. 



(783.) In Bibio febrilis (fig. 150, B), the sucking disks appended to 

 the foot are three in number, but in other respects their conformation 

 is the same. 



