266 INDIRECT BENEFITS DERIVED FROM INSECTS. 



easy, as I have experienced, than to clear a plant or 

 small tree by placing- upon it several larvas of Coccinel- 

 laB or of aphidivorous flies collected from less valuable 

 vegetables. 



Lastly, to close this list of imparasitic insectivorous 

 larvs, I may mention those of Latreille's genus Volu- 

 cella (Sj/rphifs, F.), 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 {Mt/rmeleon) and Reaumur's improperly 

 named worm-lion {R/tagio, F.), whose singular strata- 

 gems will be detailed in a subsequent letter, both of 

 which destroy great numbers of insects that are so un- 

 fortunate as to fall into their toils. 



The parasitic \sii'\'ss, an extremely numerous tribe, 

 must next be considered. These, with the exception of 

 a very few individuals, belong to the order Ihjmcno- 

 ptera, and were included by Linnc under his vast genus 

 Ichneumon y so named from the analogy between their 

 services and those of the Egyptian Ichneumons ( Viterra 

 Ichneumon, L.), the former being equally important 

 as destroyers of insects, with the latter as devourers of 

 serpents, the eggs of crocodiles, &c. 



The habits of the wliolc of this tribe, winch properly 

 includes a great number of distinct genera, are similar. 

 They all oviposit in living insects, chiefly while in the 

 larva state, sometimes while pupje (Ich. Puparum, L.) ; 

 and ev^en while in the e^^ state {Ich. Ovulorum, L.); 

 but not, as far as is known, in perfect insects. The 

 eggs thus deposited soon hatch into grubs, which im- 

 mediately attack their v ictim, and in the end insure its 

 destruction. The number of eggs committed to each 



