288 THE LEPIDOPTERA. 



always efficient biting organs. In the Lepidoptera, 

 on the contrary, the mandibles are reduced to the 

 merest rudiments, concealed beneath the hairs with 

 which the front of the head is clothed, and between 

 them we find the labrum or upper lip in a correspond- 

 ingly rudimentary condition. Beneath these we see 

 the suctorial organ, the most characteristic peculiarity 

 of the Lepidoptera, in the form of a slender spiral 

 trunk reposing between a pair of large hairy cushions. 

 The structure of this trunk has been sufficiently de- 

 scribed already (see p. 14). It varies considerably 

 in length, and is sometimes even quite rudimentary ; 

 but, as a general rule, it is long, slender, and taper- 

 ing, and coiled up when at rest in a beautiful spiral 

 under the front of the head, from which, however, it 

 can be extended at the pleasure of the insect, for the 

 purpose of sucking up the nectar of flowers, on which 

 alone these insects live. 



But besides these peculiarities of the mouth, the 

 insects of this Order generally present several external 

 characters, which will enable them to be recognized 

 at the first glance. Amongst these the most striking 

 consists in the nature of the wings, which are almost 

 always present, four in number, of large size, mem- 

 branous, and traversed by a considerable number of 

 veins running in a longitudinal direction. The mem- 

 brane, however, instead of being naked and trans- 

 parent as in most other insects, or simply clothed 

 with a few hairs as in the Trichoptera } is usually 

 covered all over, and on both surfaces, with minute 

 scales, which are often of singular forms, and of the 

 most varied colours. These scales, however, are in 

 reality only modifications of the hairs which we find 

 scattered over the wings of many other insects j they 



