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 antennae. 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 same nature as the simple eyes of spiders, and the 

 stemmata of various kinds of insects. The antennae, 

 often the most conspicuous appendages of the head 

 in perfect insects, are very minute in lepidopterous 

 larvae, 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 i number, and are placed in a 



