THE ICHNEUMONS. 241 



Not only are insects of all kinds more or less sub- 

 jected to the dominion of these little destroy ers^ but 

 they are also liable to their attacks in all stages of 

 their existence. The eggs of many species_, minute 

 as they are, serve as the habitation of the larvae of 

 still more diminutive parasites, which find ample 

 room and nourishment even within this small com- 

 pass to enable them to reach their full development, 

 and undergo their metamorphosis. Nay, so exceed- 

 ingly minute are some of these egg-parasites, that, 

 according to Mr. Haliday, a single butterfly's egg 

 may supply the necessary food for many individuals. 



But by far the greater number of these parasitic 

 Hymenoptera deposit their eggs in the larvae of other 

 insects, in the interior of which theii* progeny live, 

 feeding upon the substance of their unfortunate host, 

 but carefully avoiding all the vital organs, so that the 

 infested larva continues feeding and growing as freely 

 as those of his fellows who bear no such disagreeable 

 inmate about with them, and even in many instances 

 undergoes his change to the pupa state without giving 

 any indication of the gnawing evil within him. In 

 these cases the parasitic larvae, after consuming the 

 whole substance of theii' victim, change to pupae in 

 the interior of his pupa-case, and only betray their 

 existence when the period for their assuming a more 

 active form arrives; but in a great many species, 

 generally when numerous parasites have feasted in 

 common upon a single larva, the Ichneumon-larvae 

 break through the skin of the latter, when, having 

 attained its full size, it is preparing for its trans- 

 formation, and spinning little silky cocoons upon 

 the empty skin or in its immediate neighbourhood, 

 undergo their change to the pupa state in the interior 



M 



