INDIRECT BENEFITS DERIVED FROM INSECTS. 153 



larvae 1 ; and the ant-lion (Myrmeleon) and Reaumur's improperly named 

 worm-lion (Leptis), whose singular stratagems will be detailed in a sub- 

 sequent letter, both of which destroy numerous insects that are so 

 unfortunate as to fall into their toils. 



The Parasitic larvae, an extremely numerous tribe, must next be 

 considered. 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, 

 &c. 



The habits of the whole of this tribe 2 , which properly includes several 

 families (Ichneumomdte, Chalcidida, &c.) 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 Pupantm) ; at others 

 while in the egg state (Pteromalus ovulorum, and bifasciatus, Chrysolampus 

 tristis, &c.). The eggs thus deposited soon hatch into grubs, which imme- 

 diately 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 uninvested by their appropriate parasite. Such is the 

 activity 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. s . 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. 4 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, 



1 Macquart, Dipteres, i. 482. 



2 Latreille denominates this family, as he calls it, Pupivora ; if by this he alludes 

 to their devouring the young of insects, from the classical meaning of the word pupa, 

 the term is very proper ; but this should be borne in mind, as the majority of readers 

 would imagine it to refer to the pupa state of insects, in which they are not so gene- 

 rally devoured by their parasites. 



3 Marsham in Linn. Trans, iii. 26. 



4 See above, pp. 92, 93. 



