222 INDIRECT BENEFITS DERIVED PROM INSECTS. 



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 

 Hymenoptera 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 Chrysidca or golden wasps feed 

 upon insects of their own order. One of the latter {Parnopes 

 incarnatci) commits her eggs to the progeny of Bemhex ros- 

 trata: another (^Chrysis bidentatd) attacks the young of 

 Epipone spinipes. 



Bemhex and Mellinus confine themselves to Diptera, the 

 former preying upon Eristalis tenax, Bomhylii, and the like ^ ; 

 the latter, amongst others, ridding us of the troublesome 

 Stomoxys calcitrans. One of these last I have observed sta- 

 tioned on dung watching for flies, which, when seized, she 

 carried to her burrow. The numerous species of Crabro Fab. 

 also store up chiefly dipterous insects in their cells, some con- 

 fining themselves to one and the same species, others ap- 

 parently taking any that offer. 



Epipone spinipes, belonging to the family of Wasps, feeds 

 upon certain green apod larvae, of which the female deposits 

 ten or twelve with each egg. The common sand-wasp {Am-" 

 mophila vulgaris^ destroys caterpillars of a larger size, and 

 most of the other Yespoid and Sphecoid Hymenoptera, viz. 

 Trypoxylon, Philanthus, Larra, &c. assist in this great work. 



Pompilus, to which genus probably several species men- 

 tioned by Reaumur as preying on these insects should be 

 referred, has it in* charge to keep the number of spiders 

 within due bounds : and some sand-wasps lend their aid. 

 One of these last, mentioned by Catesby (^Sphex ccsruleus), 

 has been known to seize a spider eight times its own weight.'^ 

 Another species of this genus, which is common in the Isle of 

 France, attacks an insect still more difficult, one would think, 

 to turn to its purpose, the all-devouring Blatta, or cock- 

 roach, and is therefore one of the great benefactors to man- 



1 Latreille, Observations nouvelles sur les Hym^nopteres. Annul de Mus. 1 1 . 



2 Nat. Hist, of Carolina, ii. 105. 



