INDIRECT BENEFITS DERIVED FROM INSECTS. 267 



this knowledge, nothing is more easy, as I have expe- 

 rienced, than to clear a plant or small tree by placing 

 upon it several larvae of Coccinellae or of aphidivorous 

 flies collected from less valuable vegetables. 



Lastly, to close this list of imparasitic insectivorous 

 larvee, I may mention those of GeofFroy's genus Volu- 

 cella so remarkable for their radiated anus, which live 

 in the nests of humble-bees, braving the fury of their 

 stings and devouring their 3'oung; and the ant-lion {Mj/r- 

 vieleon) and Reaumur's improperly named worm-lion 

 (Leptis), whose singular stratagems will be detailed in 

 a subsequent letter, both of which destroy great numbers 

 of insects that are so unfortunate as to fall into their 

 toils. 



The parasitic larv£e, an extremely numerous tribe, 

 must next be considered. These, with the exception of 

 a very few individuals, belong to the order Hymcno- 

 ptera, and were included by Linne under his vast genus 

 Ichneumon^ so named from the analogy between their 

 services and those of the Egyptian Ichneumons {Viveira 

 Ichneumon), the former as destroyers of insects, being 

 equally important with the latter as devourers of ser- 

 pents, the eggs of crocodiles, &c. 



The habits of the whole of this tribe*, which properly 



includes a great number of distinct genera, are similar. 



They all oviposit in living insects, chiefly while in the 



larva state, sometimes while pupa3 {Misocampus Pupa- 



^ Latrcille denominates this family, as he calls it, Pupivura : if by 

 this he alludes to their devouring the j/o?<);g of" insects, from the clas- 

 sical meaning of the word pupa, the term is \qy^ 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 arc not so ge- 

 nerally devoured by their parasites. 



