The Life-History and Anatomy of Butterflies 
Fig. 27.— 
Chrysalis of 
Pieris olera- 
cea (Riley). 
draws near, it is in many cases possible to discern through the 
thin, yet tough and hard, outer walls of the chrysalis the spots and 
colors on the wings of the insect. 
Duration of Pupal Life. — Many butterflies remain in the chrys¬ 
alis stage only for a few weeks; others hibernate in this state, and 
in temperate climates a great many butterflies pass the winter as 
chrysalids. Where, as is sometimes the case, there are two or 
three generations or broods of a species during the year, the life 
of one brood is generally longer than that of the 
others, because this brood is compelled to over¬ 
winter, or hibernate. There are a number of but¬ 
terflies known in temperate North America which 
have three broods: a spring brood, emerging from 
chrysalids which have overwintered; an early sum¬ 
mer brood; and a fall brood. The chrysalids in the 
latter two cases generally represent only a couple 
of weeks at most in the life of the insect. In 
tropical and semi-tropical countries many species re¬ 
main in the chrysalis form during the dry season, and emerge at 
the beginning of the rains, when vegetation is refreshed and new 
and tender growths occur in the forests. 
The Transformation from the Chrysalis to the Imago.— The 
perfectly developed insect is known technically as the imago. 
When the time of maturity in the chrysalis state has been reached, 
the coverings part in such a way as to allow of the 
escape of the perfect insect, which, as it comes 
forth, generally carries with it some suggestion of 
its caterpillar state in the lengthened abdomen, 
which it with apparent difficulty trails after it until 
it secures a hold upon some object from which 
it may depend while a process of development 
(which lasts generally a few hours) takes place pre¬ 
paratory to flight. The imago, as it first emerges, 
is provided with small, flaccid wings, which, to¬ 
gether with all the organs of sense, such as the 
antennae, require for their complete development 
the injection into them of the vital fluids which, 
upon first emergence, are largely contained in the 
cavities of the thorax and abdomen. Hanging pendant on a pro¬ 
jecting twig, or clinging to the side of a rock, the insect remains 
1 3 
Fig. 28. —But¬ 
terfly (Papilio 
aster ias ) just 
emerging from 
chrysalis. 
