22 THE BUTTERFLIES OF THE 



a muscular pad, by whose expansions and contractions 

 the larva moves. 



The Papilios have in the upper part of the second 

 segment a peculiar V-shaped extensile appendage, known 

 as a "scent-organ," or osmateria, which they protrude 

 from a transverse slit when disturbed, but which is at other 

 times concealed. This organ is without doubt used as a 

 defense, the disagreeable odor emitted repelling enemies. 

 In some of the Lyca?nida? the posterior part of the body 

 has extensile organs that secrete a sweet fluid which is 

 eaten greedily by ants. These in turn guard the larva? 

 against the attacks of ichneumon-flies, very much as they 

 protect plant-lice from the attacks of enemies for the 

 sweet fluid they get from the honey-tubes of the lice. 



In passing from the eggs to the full-grown larvae, 

 caterpillars moult or shed their skins from four to five 

 times. At each moult they not only come out in a skin 

 that is larger than the old one, which thus permits further 

 growth, but the color and other markings are usually 

 changed. 



In habits of feeding each species has its larval peculi- 

 arities. Some feed singly, as the larva? of Grapta Comma, 

 on the under side of a hop- or nettle-leaf. Some stitch 

 together the edges of a leaf, making a more or less closed 

 retreat ; others feed on the surface without any attempt 

 at concealment, as Papilio Oresphontes, but here the color 

 and shape so mimic an object which would be distasteful 

 to birds that it is not molested by them. The young 

 larva? of Apatura are gregarious, but are not protected 

 by a web. After the third moult they scatter, and the 

 rest of the time are solitary, llelitcea Phaeton larva? 

 make a web, within which they feed till after the third 



