276 MOTIONS OF INSECTS. 



supply the want of legs by means of claws at their anus< 

 Thus that of the flesh-fly, Ray tells us in the place just 

 quoted, pushes itself by the protruded spines of its tail. 

 The larva also of a long-legged gnat (Tipiila repUcata, 

 Lr.), which in that state lives in the water, is furnished 

 with these anal claws, which, in conjunction with its an- 

 nular tension and relaxation, and the hooks of its mouth, 

 assist it in walking over the aquatic plants*. 



A remarkable difference, according to their station, 

 obtains in the bots of gad-flies : those that are subcutane- 

 ous {Ciiticoloe^ Clark) having no unguiform mandibles ; 

 while those that are gastric {Gastricolce, Clark), and 

 those that inhabit the maxillary sinuses of animals {Ca- 

 vicoice, Clark), are furnished with them. In this we evi- 

 dently see Creative Wisdom adapting means to their 

 end. For the cuticular bots having no plane surface to 

 move upon, and imbibing a liquid food, in them the 

 mandibular hooks would be superfluous. But they are 

 furnished with other means by which they can accomplish 

 such motions, and in contrary directions, as are neces- 

 sary to them ; the anterior part of each segment being- 

 beset with numbers of very minute spines, not visible 

 except under a strong magnifier, sometimes arranged 

 in bundles, which all look towards the anus ; and the 

 posterior part is as it were paved with similar hooks, but 

 smaller, which point to the head. '^Phus we may con- 

 ceive, when the animal wants to move forward, that it 

 pushes itself by the first set of hooks, keeping the rest, 

 which would otherwise impede motion in that direction, 

 pressed close to its skin — or it may depress tliat part 



' De Gcer, vi. 355. 



