INSECTS 



ENTOMOPHAGA 



Ichneumons and their Allies 



This group comprises several thousands of species, of which, 

 though some are of moderate size, the great majority are very small 

 .and obscure, and in the present imperfect state of our knowledge the 

 study of most of them is attended with considerable difficulty ; for while 

 many are excessively variable, others though abundantly distinct are 

 superficially so much alike, and their specific distinctions are so minute 

 and so easily overlooked, that only a very few experts are able to deter- 

 mine them with certainty. 



They are divided into several sections, which include the Cbrysididte, 

 the Icbneumonidcf, the Braconida, the E-vaniidee, the Chalcidida and the 

 Proctotrupida. As a rule they are parasitic upon other insects, a large 

 proportion of them passing their earlier stages in the larva? of the Lepi- 

 doptera. The Chrysididce or Ruby-tailed flies are not very numerous in 

 Britain, and their proper place is perhaps rather with the Aculeata than 

 the Entomophaga. They prey upon certain of the bees and wasps, laying 

 their eggs in the burrows of their victims after the manner of the cuckoo 

 bees. They are extremely beautiful insects, being resplendent with 

 brilliant blue, green, crimson, burnished copper and other gorgeous 

 colours. The Ichneumonidce, Eraconidce and E-vaniida deposit their eggs 

 principally upon or in the larva? and ova of the Lepidoptera, but they 

 attack other insects and also spiders ; and upon the efficient discharge 

 of their important functions the welfare of the world depends to a far 

 greater extent than the world generally is at present aware of. For if 

 all insects were allowed to increase without let or hindrance, they would 

 multiply at such a prodigious rate that every green leaf would speedily 

 be devoured by them. It is quite true that other agencies, such as 

 insectivorous birds, are also at work in keeping them in check, but it is 

 probably not going too far to say that the birds are but the Sauls who 

 slay their thousands while the ichneumons are the Davids who slay their 

 tens of thousands. Nay, it is highly probable that by far the larger 

 portion of those larva? which are consumed by birds would perish in any 

 case from the attacks of ichneumons, and more than possible that in 

 many instances the attacks of birds, though immediately fatal to multi- 

 tudes of individual larvae, may be ultimately beneficial to the species to 

 which they belong by the wholesale destruction of its far more inveterate 

 and insidious foes. 



But while of the innumerable larva? that emerge from the egg very 

 few escape from the attacks of the ichneumon, Nature is also careful of 

 her children in more ways than one ; for when a parasite becomes so 

 numerous as to threaten the extinction of a race, it is very frequently 

 itself preyed upon by a hyper-parasite, which attacks it after a similar 

 fashion. 



The Chalcididee are for the most part extremely minute brilliantly 

 coloured insects, with habits similar to those of the Ichneumonidcc. The 



in 



