1*24 OX THE CATERPILLARS 



although those of the Zepidoptera have the colours 

 generally more distinct and varied. 



The breathing pores are placed in both groups along the 

 sides of the body, but they are more indistinct in the larvae 

 of the saw-flies. Both, also, have three pairs of scaly- 

 articulated legs, and a number of fleshy prolegs placed on 

 the hinder segments of the body ; these prolegs are, how- 

 ever, considerably more numerous in the larvae of the saw- 

 flies, the smallest number (where they exist at all) being 

 six pairs, whilst many have seven and even eight pairs, 

 whereas the greatest number of prolegs in any Lepidopterous 

 larva is ten, namely, four pairs of ventral and one pair of 

 anal prolegs ; moreover, the prolegs of Lepidopterous larvae 

 are armed with a coronet of minute curved spines or 

 hooklets, of which the prolegs of the saw-fly larvae are 

 destitute. 



The form of the head and its organs, although presenting 

 a general similarity, offers certain points of difference in the 

 two groups. Indeed the form of the head varies much in 

 different Lepidopterous larvae, but the head of the larvae of 

 the saw-flies is formed on a single model, unlike, in its 

 details, that of the head of any Lepidopterous larva, being 

 short, rounded or somewhat spherical and rather flattened 

 in front. Moreover they possess only a single eye on each 

 side of the head, of a size sufficiently large to be seen with 

 the naked eye, whilst the heads of caterpillars are provided 

 with five or six much smaller eyelets on each side, placed a 

 little higher than the base of the mandibles 



With reference to that important organ, the mouth, al- 

 though the structure of the bilobed upper lip, and the 

 short, triangular, multidentate mandibles, is very similar 

 in the larvae of both groups, that of the lower parts of the 

 mouth is much more distinct. The saw-fly larvae (at least 



