194 AFFECTION OF INSECTS FOR THEIR YOUNG. 



pupae, nay the very eggs of these animals, are not safe from their insidious 

 manoeuvres. The size of the different species varies in proportion to that 

 of the bodies which are to be their food; some being 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 1 ; others so large that the 

 body of a full-grown caterpillar is not more than enough for one. They 

 are the larvae of these Ichneumons which make such havoc of our pigmy 

 tribes : the perfect insect is a four-winged fly, which takes no other food 

 than a little honey; and the great object of the female is to discover a 

 proper nidus for her eggs. In search of this she is in constant motion. 

 Is the caterpillar of a butterfly or moth the appropriate food for her 

 young ? you see her alight upon the plants where they are most usually 

 to be met with, run quickly over them, carefully examining every leaf, 

 and, having found the unfortunate object of her search, insert her sting 

 into its flesh, and there deposit an egg. In vain her victim, as if conscious 

 of its fate, writhes its body, spits out an acid fluid, menaces with its ten- 

 tacula, or brings into action the other organs of defence with which it 

 is provided. The active Ichneumon braves every danger, and does not 

 desist until her courage and address have insured subsistence for one of 

 her future progeny. Perhaps, however, she discovers, by a sense the 

 existence of which we perceive, though we have no conception of its 

 nature, that she has been forestalled by some precursor of her own tribe, 

 that has already buried an egg in the caterpillar she is examining. In this 

 case she leaves it, aware that it would not suffice for the support of two, 

 and proceeds in search of some other yet unoccupied. The process is of 

 course varied in the case of those minute species of which several, some- 

 times as many as 150, can subsist in a single caterpillar. The little Ich- 

 neumon then repeats her operations, until she has darted into her victim 

 the requisite number of eggs. 



The larvae hatched from the eggs thus ingeniously deposited, find a 

 delicious banquet in the body of the caterpillar, which is sure eventually 

 to fall a victim to their ravages. So accurately, however, is the supply of 

 food proportioned to the demand, that this event does not take place 

 until the young Ichneumons have attained their full growth ; when the 

 caterpillar either dies, or retaining just vitality enough to assume the pupa 

 state, then finishes its existence ; the pupa disclosing not a moth or a 

 butterfly, but one or more full-grown Ichneumons. 



In this strange and apparently cruel operation one circumstance is truly 

 remarkable. The larva of the Ichneumon, though every day, perhaps for 

 months, it gnaws the inside of the caterpillar, and though at last it has 

 devoured almost every part of it except the skin and intestines, carefully 

 all this time avoids injuring the vital organs, as if aware that its own exist- 

 ence depends on that of the insect on which it preys! Thus the cater- 

 pillar continues to eat, to digest, and to move, apparently little injured, to 

 the last, and only perishes when the parasitic grub within it no longer re- 

 quires its aid. What would be the impression which a similar instance 

 amongst the race of quadrupeds would make upon us ? If, for example, an 

 animal such as some impostors have pretended to carry within them 

 should be found to feed upon the inside of a dog, devouring only those 

 parts not essential to life, while it cautiously left uninjured the heart, 



i Bonnet, ii. 314. 



