276 HALF HOURS WITH INSECTS. [Packard. 



extinctions and creations of new faunas out of preceding 

 ones, as are indulged in by naturalists of tlie present day, in 

 the light of the knowledge pouring in upon them from Arctic 

 explorers and western geologists ? Granted these extraordi- 

 nary changes in the phj'sical surroundings of the animals 

 whose descendants people our land, do not a host of ques- 

 tions arise as to the result in the beings of our day of these 

 changes in the modes of life, the modes of thought, so to 

 speak, the formation of peculiar instincts arising from new 

 exigencies of life, which have remodelled the whole psychol- 

 og}', as it were, of the animals of our country? Instincts 

 vary with the varying structure and form of the animals. 

 Change the surroundings, and at once the mode of life and 

 psj'chology of the organism begin to undergo a revolution. 

 These changes may result in the gradual extinction of M^hole 

 assemblages of animals, which are as gradually replaced by 

 new faunas. 



Many, indeed most, insects are in our northern hemisphere 

 represented in the colder months of the year by the chrysa- 

 lis or eggs. These are eagerly sought after by the smaller 

 birds, and are in most cases protected by their colors, or by 

 their resemblance to the bark of the trees on which they 

 may be laid. The eggs of the canker worm are gra}^, like 

 the bark of the tree or paling on which they are deposited. 

 The eggs of the tent caterpillar are covered over with a 

 coating of gum, so that the bunch looks like an excrescence 

 on the tree. The chrj'salis of Vanessa Antiopa is exactly 

 of the color of old wood, and it is often found hanging from 

 fences and out-houses, while, before houses were built, for 

 this butterfly belongs to an ancient family, it assimilated in 

 hue the bark of trees. The cocoons of many of the silk 

 moths, like those of the Promethea moth, are covered with 

 leaves drawn around them in the process of weaving, and 

 hang all winter on the wild cherr^^, having the semblance of 

 a dead leaf. Those of the Polyphemus (Fig. 214) which fall 



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