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 larvse of Coccinellse or of aphidivorous 

 flies collected from less valuable vegetables. 



Lastly, to close this list of imparasitic insectivorous 

 larvae, I may mention those of Geoffrey'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 young ; and the ant-lion (Myr- 

 meleori) 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 larvae, an extremely numerous tribe, 

 must next be considered. These, with the exception of 

 a very few individuals, belong to the order Hymeno- 

 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 (Viverra 

 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 a , 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 pupae (Misocampus Pupa- 



a Latreille denominates this family, as he calls it, Pupivora: if by 

 this he alludes to their devouring the young of insects, from the clas- 

 sical 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 ge- 

 nerally devoured by their parasites. 



