PABASITES THAT ABE FKEE WHEN OLD. 165 



time of which varies more or less according to the 

 species, each ichneumon takes his departure, seeks for 

 booty on his own account, and passes through the last 

 stages of his existence at full liberty in the open air. 

 Nothing is more beautiful than this insect in the plenitude 

 of its life. The species of the ichneumon are very 

 numerous. Mons. Wesmael has devoted a part of his 

 life to the study of these insects. 



We often ask ourselves what can be the use of these 

 little creatures — what good purpose can be effected by 

 vermin which annoy everybody ? Michelet replied to 

 this question when he wrote "The Insect." "Birds," 

 says the brilliant historian, " prefer to destroy those 

 insects which are the most injurious." We may say the 

 same of those which we are now considering. The most 

 common caterpillar, and that which is the most dreaded 

 on account of its great fecundity, is precisely that which 

 is more eagerly sought by the greater number of ichneu- 

 mons. No less than thirty-five kinds of these little 

 assassins fall on certain species, to make them serve as 

 a quarry to be given to their young ones. The Bombyx 

 pini is one of the most dangerous and destructive insects 

 in our woods. The ichneumons would seem to take into 

 consideration the too great fecundity of this moth, and 

 instead of one species, as is often the case, thirty-five 

 different species direct their attacks upon it. It would 

 be indeed difficult for the mother to withdraw her young 

 ones from the ovipositors of so many enemies, but there 

 will be always enough of them remaining to keep up the 

 balance in this little world ; the greatness of the danger 

 with respect to plants will be counterbalanced by the 

 number of ichneumons which arrest the propagation of 



