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 



13 



Fig. 28. — But- 

 terfly (Papilio 

 aster ias) just 

 emerging from 

 chrysalis. 



