INTRODUCTION. 67 



Asellus and Limacodes Testudo), they are entirely 

 wanting, their place being supplied by a number of 

 small simple tubercles. The larvse of a great pro- 

 portion of the largest and most conspicuous of oar 

 native moths are provided with ten prolegs, like 

 those of butterflies, and placed in the same order. 

 In many others there are only eight, either one of 

 the abdominal pairs, or the anal one, being absent. 

 When the latter is the case, the hinder extremity 

 of the body sometimes bears two caudal appendages 

 (as may be seen in the caterpillars of the Puss and 

 Lobster moths), with the free motions of which a 

 pair of anal legs would probably interfere. Many 

 larvse possess only six prolegs, others four, and a 

 few of the smaller kinds merely a single pair, attached 

 to the anal segment. Such as have a considerable 

 number of intermediate legs generally keep their 

 body, when walking, parallel with the plain of posi- 

 tion, and advance by the rapid and successive motion 

 of each segment, as if, as has been happily remarked, 

 a wave were flowing over or pervading their bodies. 

 But such a mode of locomotion evidently cannot take 

 place when most or all of the abdominal segments 

 $re without legs, as is the case with some of those 

 just mentioned. These accordingly adopt a different 

 method, by means of which they are enabled to 

 move about with ease and celerity. They first fix 

 their prolegs to the plain of position and stretch the 

 body forward to its full extent ; then laying hold 

 with the anterior legs, the tail is let free and drawn 

 towards the head, the intervening portion of the 





