INTRODUCTION. XXI 



case with the egg-classification, which brings into juxtaposition 

 groups with so little apparent affinity as the Pieridcz and the 

 Libytheidm. 



But this is only an instance of the difficulties we encounter 

 at every step in entomology, both on account of the vast 

 number of species with which we have to deal, and the various 

 forms of each species, to say nothing of the enormous number 

 of petty details, which prevents any man from attempting to 

 study more than a very small branch of the subject thoroughly. 



When the enclosed larva is ready to emerge, it pushes off 

 the lid of the egg, or eats its way out, and appears as the 



Larva or Caterpillar. 



The term " larva " means "a mask" in Latin, and is technically 

 applied to the second stage of all insects. " Caterpillar " is a 

 popular term applied to the same stage of Lepidoptera only. 

 True Caterpillars never have more than sixteen legs (except, 

 possibly, in one or two little-known exotic species), though 

 those of a whole family of Moths (the Geometrida) have only 

 ten ; and some of the Micro-Lepidoptera have hardly any. 

 The larvae of some of the Saw-flies ( Tentliredinidce) are often 

 called " False Caterpillars." They frequently much resemble 

 true caterpillars, but have from eighteen to twenty-two legs, or 

 else no legs at all. In certain genera of Saw-flies, too, the 

 antennas of the perfect insect are clubbed, a character which, 

 though met with occasionally in all orders of insects, is compara- 

 tively infrequent, except in the case of Butterflies and Ant- 

 Lions, and other allied Nearoptera. 



" The body of caterpillars is long and nearly cylindrical, and 

 is divided by deep incisions into twelve segments, exclusive of 

 the head. The outer integument, or skin, is usually mem- 

 branous and soft, but in some instances it approaches more to 

 a coriaceous texture. The general softness of the body is of 

 great utility, as it thereby acquires great flexibility, and easily 



