INTRODUCTION 



THE object of the explanations given in. this portion of the 

 present work is solely to make the subsequent portion intelli- 

 gible, and no subject is discussed in greater detail than is 

 necessaiy for that purpose. Hence no account is given of the 

 internal organs belonging to the digestive, nervous, and mus- 

 cular systems, which, so far as studied, have not yet been 

 found to present characters available for use in classification. 



The Lepidoptera are amongst those insects in which the life 

 of the organism, after leaving the egg, is marked by a series 

 of well-defined changes in structure and habits. In the case 

 of the Lepidoptera three separate stages (besides the egg) are 

 constituted, each with its appropriate function ; (1) the larva 

 (or caterpillar), whose function is growth ; (2) the pupa (or 

 chrysalis), whose function is maturation ; and (3) the imago 

 (or perfect insect), whose function is reproduction. 



Structure of Imago. 



All the details of structure hereafter mentioned can be 

 observed with a simple lens of moderate power ; but a strong 

 lens (such as a platyscopic or Coddington) will sometimes be 

 found useful. In the examination of obscure details the proper 

 management of the light is essential ; if the illumination of 

 the object is satisfactory, the magnifying power of the lens is 

 a secondary consideration. 



A Lepidopterous insect is regarded as normally composed of 

 thirteen segments, of which one (really consisting of several 

 segments fused together) forms the head, three the thorax, and 

 the remaining nine the abdomen, though one or two terminal 

 segments of the abdomen are often much modified and little 

 recognisable ; four wings and six legs are usually present as 

 paired appendages of the thorax, but in certain cases are not 

 developed. 





