THEIR INSTINCT. 127 



The instinct of these extraordinary creatures 

 leads them to the most complete regulation of 

 the number of their eggs by the size of the 

 victim in each case, and that of the larvae to 

 which they are to give birth. Sometimes they 

 lay a single egg where there is only enough for 

 the support of its grub, but the numbers vary 

 from one to a large quantity. There is scarcely 

 an insect in existence that is not more or less 

 subject to this species of attack ; and the ich- 

 neumons themselves vary in size according to 

 the dimensions of the bodies on which they are 

 destined to prey. " Some,'* says Mr. Kirby, 

 "are so inconceivably small, that the egg of a 

 butterfly, not bigger than a pin's head, is of 

 sufficient magnitude to nourish two of them to 

 maturity ; others so large, that the body of a 

 full-grown caterpillar is not more than enough 

 for one." It is not the ichneumon itself, but 

 its larva, or maggot, which destroys such quan- 

 tities of insects. The ichneumon is a fly with 

 four wings, whose food is honey, and the female 

 seems to live only for the purpose of depositing 

 eggs in the way mentioned. " In search of 

 this," we are told by the aged entomologist just 

 alluded to, " she is in constant motion. Is the 

 caterpillar of ^a butterfly or moth, the appro- 



