EASTERN UNITED STATES. 25 



being fastened into the button of silk to which the anal 

 legs were attached before changing from the larva to the 

 pupa state. The joints back of the wing-cases are more 

 or less movable. In the chrysalides of the Papilios the 

 lateral ridges of the cephalo-thorax are continuous to the 

 cremaster ; in others, as some of the Nymphalidae, there 

 are rows of tubercles or spines. In all cases the abdomen 

 contains a row of stigmata on either side which corre- 

 spond to those in the larva, except the anterior, whose 

 places are covered by the wing-cases. 



The outside covering of the chrysalis is a fine, horny 

 substance known as chitine, the same as forms the hard 

 [>arts of all insects. In most of the pupae this is in color 

 gi'eenish, yellowish gray, or some shade of brown, some- 

 times ornamented with bright metallic spots. 



While the pupal period seems externally to be one of 

 inactivity, internally great changes are going on, — the 

 preparation for a change from the worm-like caterpillar, 

 which can only creep or slide over a leaf or twig, to the 

 airy and graceful butterfly. The time in which this 

 change takes place, the pupal period, varies greatly, 

 ranging from six or seven days to several months, as 

 with those that hibernate in this state ; but about four- 

 teen days is the usual time. 



When the pupal period draws to a close, the pupa-case 

 is burst open on the dorsal part of the cephalo-thorax, 

 and the butterfly, or imago, emerges with all its parts 

 limp and moist. This bursting of the case is accom- 

 plished partly by the moisture that is exuded from the 

 interior for the purpose of softening the inner integu- 

 ment of the shell, and partly, it seems, by favorable 

 atmospheric conditions, as the moist atmosphere of a 



B 3 



