MOTIONS OF INSECTS. 285 



organs consist of three or four folds, and are commonly 

 terminated, though not always, by a coronet or semicoro- 

 net of very minute crooked claws or hooks. These claws, 

 which sometimes amount to nearly a hundred on one 

 proleg, are alternately longer and shorter. They are 

 crooked at both ends, and are attached to the proleg by 

 the back by means of a membrane, which covers about 

 two-thirds of their length, leaving their two extremities 

 naked. Of these the upper one is sharp, and the lower 

 blunt. The sole, or part of the prolegs within the claws, 

 is capable of opening and shutting. When the animal 

 walks, that they may not impede its motion, it is shut, 

 and the claws are laid flat with their points inwards ; but 

 when it wishes to fix itself, the sole is opened, becoming 

 of greater diameter than before, and the claws stand 

 erect with their points outwards. Thus they can lay 

 stronger hold of the plane of position^. 



The number of these prolegs varies in different spe- 

 cies and families. In the numerous tribes of saw-flies 

 {Serrifern), the larvae of which resemble those of 

 Lepidoptera, and are called by Reaumur spurious cater- 

 pillars [fausses chenilles)^ one family {Tjoph^jrus) has six- 

 teen prolegs ; a second [Hylotoma, &c.) fourteen ; an- 

 other {Tenthredo, F.) twelve; and a fourth {Lyda) none 

 at all, having only the six perfect legs. The majority 

 of larvae of Lepidoptera have ten prolegs, eight being 

 attached, a pair on each, to the sixth, seventh, eighth, 

 and ninth segments of the body, and two to the twelfth 

 or anal segment^. The caterpillar of the puss-moth 



different name from perfect legs, and at the same time one that 

 showed some affinity to them. 



^ Lyonet, 82-/. iii./. 10-16. " Ibid. t. i.f. 4. 



