26 THE COMMONER BUTTERFLIES. 



One of these concerns the mode of transformation. In 

 the moths, with very few exceptions, a cocoon or cell is 

 formed within which the transformations take place. The 

 Skippers form a cocoon, bnt lighter than is common among 

 the moths, and in addition (j^erhaps not universally, but 

 very generally) the chrysalids are loosely swung up within 

 the cocoon by the Y-shajied shrouds mentioned above. 

 The Typical Butterflies retain the shrouds though they droj") 

 the cocoon, but, as the result, the hinder shrouds become a 

 mere pad of silk, the median shrouds a loose loop. The 

 only change in the Gossamer-winged Butterflies is the tight- 

 ening of the median loop and the flattening of the ventral 

 surface of the chrysalis to correspond. Lastly in the Brush- 

 footed Butterflies the median loojo is dropped and the chry- 

 salis hangs by the tail-fastenings alone, while the straight 

 ventral surface is generally retained — a significant atavistic 

 indication of the girt stage. 



The other regards the structure of the forelegs of the 

 imago. In the Skippers these agree perfectly with the other 

 legs (as in the moths), except in the presence of a median 

 spine on the tibiae. The same is true of the Typical Butter- 

 flies excepting that the median spine is wanting in one of 

 the two subfamilies (Pierids) regarded as the further re- 

 moved from the Skij)pers. In the Gossamer-winged But- 

 terflies atrophy has begun, but is insignificant excepting 

 in the male sex. While in the Brush-footed Butterflies 

 atrophy in both sexes has extended to complete disuse in 

 both, though usually more excessive in the male than the 

 female; one subfamily, nearest to the Gossamer-winged 

 Butterflies, partakes in this particular of the characters of 

 the latter, namely, the Snout Butterflies or Long Beaks 

 (Libytheinae). 



