ICHNEUMON FLIES. 277 



eggs : they remove them many times in a day^, eitlier 

 nearer to the surface of the ground^, or deeper below it;, 

 according as the heat or moistm-e of the weather varies. 

 One species of ichneumon fly digs a hole in the earth, 

 and, after carrying two or three living caterpillars into 

 it, deposits her eggs there, then nicely closes up the 

 nest with leaves ; providing, in this artful manner, as 

 if she had foresight, warmth to hatch her young, and 

 food for their sustenance when brought to life. Some 

 ichneumons lay their eggs in the backs of caterpillars, 

 where their maggot is nourished with that substance 

 that is converted into the silk thread of which the 

 future cocoon is formed. 



Insects that go through several transformations 

 often place their eggs where they may find food of a 

 different nature from that which they themselves con- 

 sume ; for example, butterflies lay their eggs on leaves, 

 though they eat honey; but let it be remembered, 

 that it is a caterpillar, and not a butterfly, that is to 

 proceed from the egg. Instinct teaches animals to ac- 

 commodate their habits to different climates. Spar- 

 rows, even in this country, are said to build their 

 nests without a covering when placed under shelter, 

 and with one when exposed to the weather. The 

 small birds of Europe, if in those countries where mon- 

 keys abound, change the form of their nests to that of 

 a long purse, suspended at the end of the bough of a 



