262 INDIRECT BENEFITS DERIVED FROM INSECTS. 



task devolves, and incalculable are the benefits which 

 they are the means of bestowing upon us ; for to them 

 we are indebted, or rather to Providence who created 

 them for this purpose, that our crops and grain, our cat- 

 tle, our fruit- and forest-trees, our pulse and flowers, and 

 even the verdant covering of the earth, are not totally 

 destroyed. Of these insects, so friendly to man, some 

 exercise their destructive agency solely while in the larva 

 state ; others in the perfect state only ; others in both 

 these states ; and lastly, others again in all the tiiree states 

 of larva, pupa, and imago. For order's sake, and to give 

 you a more distinct view of the subject, I shall say some- 

 thing on each separately. 



The first, those which are insectivorous only in their 

 larva state, may be further subdivided into ^arcrsiVes and 

 imparasitcs, meaning by the former term those that feed 

 upon a living insect, and only destroy it when they have 

 attained their full growth ; and by the latter, those that 

 prey upon insects already dead, or that kill them in the 

 act of devouring them. 



The imparasitic insect devourers chiefly belong to the 

 Hymenoptcra order; and though it is in the larva state 

 that their prowess is exhibited, the task of providing the 

 prey is usually left to the female, of which each species 

 for the most part selects a particular kind of insect. Thus 

 many species of Cerceris and the splendid Chrysidcc or 

 golden wasps feed upon insects of their own order. One 

 of the latter {Pamopcs incamaia) commits her eggs to 

 the progeny o^ Bcmbcx rostrata: another [C/nysis bidcn- 

 lata) attacks the young oi Epipojie spinipcs. 



Bc7nbex and Mclliims confine themselves to Diptcra, 



