72 
INTRODUCTION. 
place where the jaws unite, and serves as a groove, 
both to give steadiness to the margin of the leaf, and 
to guide it in the direction most favourable for the 
jaws to act upon it. 
The only remaining organs to which it is neces- 
sary to allude, are the eyes and antennte. The former 
appear as small dark-coloured points, arranged in two 
circles, containing six each, on the anterior part of the 
head. These points vary in size, and seem to be of 
the Bame nature as the simple eyes of spiders, and the 
stemmata of various kinds of insects. The antenna, 
often the most conspicuous appendages of the head 
in perfect insects, are very minute in lepidopterous 
larva, usually consisting of two or three short joints. 
They are almost always of a conical form, and many 
species have the power of drawing the joints within 
each other, like the tubes of a telescope, till they are 
wholly concealed. 
Many caterpillars of the day-flying Lepidoptera 
are smooth on the surface, or covered only with a 
very short matted pubescence ; but in some cases 
they are furnished with rigid hairs, and numerous 
long spines. These hairs are sometimes simple, but 
more commonly they have a series of small pointed 
pieces springing from each side, like leaves from a 
stem. They are seldom planted irregularly over the 
surface of the skin, but usually issue from a tubercle, 
and diverge in all directions. These tubercular ele- 
vations vary greatly in number, and are placed in a 
