INTRODUCTION. 71 



power of emitting a short retractile vesicle from 

 some one of the abdominal segments; and the 

 caterpillar of the Emperor-moth has a perforated 

 tubercle in front of the pectoral legs, through which, 

 when disturbed, it squirts a transparent fluid. This 

 is evidently given for defence, but with regard to 

 most of the appendages previously mentioned, and 

 others of a similar kind, we are wholly unacquainted 

 with their use. 



Many of them are almost wholly free from hairs 

 and pubescence, but in numerous instances these 

 form one of the most striking characters belonging 

 to them. Although much more varied in the 

 clothing of their bodies than butterfly larvae, they 

 are devoid of the strong spines formerly described 

 as characterising many of the latter*. These haira 

 are of different kinds, and arranged in a variety of 

 methods. Sometimes they are soft and decumbent : 

 at other times, long, slender, and tortuous, investing 

 the body as with a fleece of wool; while in other 

 instances they are long and stiff resembling bristles. 

 Frequently they are all directed backwards, at other 

 times they are turned towards the head, and in some 

 cases they are nearly all pointed upwards or down- 

 wards so as to cover the back or belly and leave the 

 opposite half of the body almost bare. In some 

 they are scattered promiscuously over the surface, 



* See vol. x. p. 65. The above remark, however, must be 

 understood as applying only to the caterpillars of British 

 moths ; those of certain exotic species are armed with spines 

 of such a size that Mr. Kirby describes them as " tre- 

 mendous." 



