232 



MOTIONS OF INSECTS. 



sus is armed with a single claw. 1 The larvae that have these 

 legs walk with them sometimes very swiftly. In stepping 

 they set forward at the same time the anterior and posterior 

 legs of one side, and the intermediate one of the other ; and 

 so alternately on each side. 



Pedate larvae are of two descriptions ; those that to perfect 

 legs add spurious ones with or without claws, and those that 

 have only perfect legs. I begin with the former — those that 

 have both kinds of legs. But first I must make a few remarks 

 upon spurious legs. Because their muscles, instead of the 

 horny substance that protects them in perfect legs, are covered 

 only by a soft membrane, they have been usually denominated 

 membranaceous legs; since, however, they are temporary, 

 vanishing altogether when the insect arrives at its perfect 

 state, — are merely used, for they do not otherwise assist in 

 this motion, as props to hinder its long body, when it walks, 

 from trailing on the ground ; to push against the plane of 

 position ; and, by means of their hooks or claws, to fix itself 

 firmly to its station when it feeds or reposes, — I shall there- 

 fore call them prolegs (propedes 2 ). These organs consist of 

 three or four folds, and are commonly terminated, though not 

 always, by a coronet or semicoronet 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, 



1 Lyonet, Tr. Anat. t. iii. f. 8. 



2 Mr. W. S. MacLeay, where quoted above, objects to this term ; but as the 

 organs in question are generally given to the animal to assist in its motions, and 

 have been universally regarded as a kind of legs, it was judged best, for the sake 

 of distinction, to give them a different name from perfect legs, and at the same 

 time one that showed some affinity to them. 



