ON THE ICHNEUMON FLY. 165 



when they are in the larva state. Sometimes they oviposit in chrysalides, 

 and occasionally in eggs, but never, it is believed, in any insect while in a 

 perfect condition. The object of their eggs being thus laid is, that they 

 may under these circumstances, which are favourable to their nature, hatch 

 into grubs. These grubs or maggots soon commence attacking the living 

 substances in which they are placed, and ultimately destroy them. 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 gi"ub, 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 

 Ichneumons 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 larger 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 larvae or maggots which destroy such 

 quantities 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 

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

 it is provided; the active Ichneumon braves every danger, and does not desist 

 till 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." Such are the singular habits of these creatures, 

 thus aptly described. All these processes are, as might be expected, varied 

 according to the number of eggs that may be placed with a hope of safe 

 existence in any one body. 



As soon as these eggs are hatched, the young maggots revel in the feast 

 the body of their victim provides, while the supply of food in every instance 

 is regulated with an inconceivable precision, so as just to last these young 

 Ichneumons till they have grown to an age to do without it. Then the 



