14 



STRUCTURE OF THE LEPIDOPTEPA 



frequently does it occur that the eggs are deposited either before 

 the flowers have appeared or after they have faded. 



Neither can we easily impute to the insect an acquired know- 

 ledge of the nature and wants of her offspring, or an acquaint- 

 ance with botany sufficient to enable her to distinguish plant 

 forms. Our only solution of the problem (which is really no solu- 

 tion at all) is to attribute the 

 whole thing to that inexplicable 

 quality which we are pleased 

 to term natural instinct. It 

 is to be observed, however, that 

 it is not all butterflies and 

 moths that display this unerr- 

 ing power. Some few seem to 

 deposit their eggs indiscrimi- 

 nately on all kinds of herbage. 

 But, I believe, the larvae of 

 these species are generally 

 grass feeders, and would sel- 

 dom^ have to travel far from 

 any spot without meeting with 

 an acceptable morsel. 



But we must now pass on 

 to a brief consideration of the 

 other stages of the insect's 

 existence, After a time, vary- 

 ing from a few days to several 

 months, the young caterpillars 

 or larvae make their appear- 

 ance. They soon commence 

 feeding in right earnest. Their 

 period of existence in this state 

 varies from a few weeks to 

 several months, and even, in 



some cases, to years. During this time their growth is generally 

 very rapid, and they undergo a series of moults or changes of skin, 

 of which we shall have more to say in a future chapter. Then, 

 when fully grown, they prepare for an apparently quiescent form, 

 which we speak of as the pupa or chrysalis, and in which they 

 again spend a very variable period, extending over a few days, 

 weeks, or months. Now, inclosed in a protective case, each pupa 



FIG. 10. THE FOUR STAGES OF THE 

 LARGE WHITE BUTTERFLY (Pieris 

 Brassicce). 

 a, larva ; 6, pupa ; c, imago ; d, egg. 



