188 INDIRECT BENEFITS DERIVED FROM INSECTS. 



The parasitic larvae, an extremely numerous tribe, jpust next be consid- 

 ered. These chiefly belong to the order Hymenoptera, and were included 

 by Linne under his vast genus Ichneumon, so named from the analogy 

 between their services and those of the Egyptian Ichneumons (^Viverra 

 Ichneumon), the former as destroyers of insects, being equally important 

 with the latter as devourers of serpents, the eggs of crocodiles, &tc. 



The habits of the whole of this tribe^, which properly includes several 

 families {Ichneumonida, Chalcidida, &tc.) and a great number of distinct 

 genera, are similar. They all oviposit in living insects, chiefly while in 

 the larva state, sometimes while pupae (^Misocampus Puparum) ; at others 

 while in the egg state {Pteromalus ovulorum, and bifasciatiis, Chrysolam- 

 pus iristis, he). The eggs thus deposited soon hatch into grubs, which 

 immediately attack their victim, and in the end insure its destruction. 

 The number of eggs committed to each individual varies according to its 

 size, and that of the grubs which are to spring from them ; being in most 

 cases one only, but in others amounting to some hundreds. 



From the observations hitherto made by entomologists, the great body 

 of the Ichneumon tribe is principally employed in keeping within their 

 proper limits the infinite host of lepidopterous larvae, destroying, however, 

 many insects of other orders; and, perhaps, if the larvae of these last fell 

 equally under our observation with those of the former, we might discover 

 that few exist uninfested by their appropriate parasite. Such is the activ- 

 ity and address of the Ichneumonidans, and their minute allies (Pupivora 

 Latr.), that scarcely any concealment, except, perhaps, the waters, can 

 secure their prey from them ; and neither bulk, courage, nor ferocity avail 

 to terrify them from effecting their purpose. They attack the ruthless 

 spider in his toils ; they discover the retreat of the little bee, that for safety 

 bores deep into timber; and though its enemy Ichneumon cannot enter its 

 cell, by means of her long ovipositor she reaches the helpless grub, which 

 its parent vainly thought secured from every foe, and deposits in it an egg, 

 which produces a larva that destroys it.- In vain does the destructive 

 Cecidomyia of the wheat conceal its larvae within the glumes that so 

 closely cover the grain ; three species of these minute benefactors of our 

 race, sent in mercy by Heaven, know how to introduce their eggs into 

 them, thus preventing the mischief they would otherwise occasion, and 

 saving mankind from the horrors of famine.^ In vain, also, the Cynips 

 by its magic touch produces the curious excrescences on various trees and 

 plants, called galls, for the nutriment and defence of its progeny : the 

 parasite species attached to it discovers its secret chamber, pierces its wall, 

 however thick, and commits the destroying egg to its offspring. Even 

 the clover-weevil is not secure within the legumen of that plant ; nor the 

 wire-worm in the earth, from their ichneumonidan foes. I have received 

 from the late Mr. Markwick that of the former, and Mr. Paul has shown 

 me the destroyer of the latter, which belongs to Latreille's genus Procto- 

 trupes. Others are not more secured by the repulsive nature of the 



• Latreille denominates this family, as he calls it, Pupivora : if by this he alludes to their 

 devouring the young of insects, Irom the classical meaning of the word pupa, the term is 

 very proper ; but this should be borne in mind, as the majority of renders would imagine it 

 to refer to the pupa stale of insects, in which they are not so generally devoured by their 

 parasites. 



* Marsham in Linn. Trans, iii. 26. * See above, pp. 126, 127. 



