INTRODUCTION. 
71 
power of eniitting 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 pectond legs, through which, 
when disturbed, it squirts a transparent fluid. This 
is evidently given for defence, but nith 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 ahnost 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*. Tliese hairs 
are of diflerent kinds, and arr;vnged 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 
instiuices they ai'e long and still' resembling bristles. 
Frequently they are all duected backwards, at other 
times they are turned towards the head, and in some 
eases they are nearly all pointed upwards or dorni- 
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 eatcrpillars of British 
moths ; those of certain exotic species are armed with spines 
of such a size that Mr. Kirby describes them as “ tre- 
mendous.” 
