INDIRECT BENEFITS DERIVED FROM INSECTS. 223 



kind. When this insect perceives a Blatta (called there 

 Kakerlac and Cancrelas) it stops immediately : both animals 

 eye each other ; but in an instant the sand-wasp darts upon 

 its prey, seizes it by the muzzle with its strong jaws, and, 

 bending its abdomen underneath it, pierces it with its fatal 

 sting. Sure of its victim, it now walks or flies away, leaving 

 the poison to work its effect ! but in a short time returns, and, 

 finding it deprived of power to make resistance, seizes it again 

 by the head, and drags it away, walking backwards to deposit 

 it in a hole or chink of a wall.^ 



Grasshoppers are the prey of another sand-wasp, supposed 

 to be the Spliex pensylvanica of Linne, a native of North 

 America, each of which in its larva state devours three of a 

 large green species with which its mother has provided it.'^ 



From none of the imparasitic insectivorous larvae do we 

 derive more advantage than from those which devour the 

 destructive Aphides, whose ravages, as we have seen above, 

 are more detrimental to us in this island than those of any 

 other insect. A great variety of species of different orders 

 and genera are employed to keep them within due limits. 

 There is a beautiful genus of four-winged flies, whose wings 

 resemble the finest lace, and whose eyes are often as brilliant 

 as burnished metals {Hemerohius), the larvae of which, Reau- 

 mur, from their being insatiable devourers of them, has 

 named the lions of the Aphides. The singular pedunculated 

 eggs from which these larvas proceed, I shall describe when 

 we come to treat upon the eggs of insects ; the larvoe them- 

 selves are furnished with a pair of long crooked mandibles 

 resembling horns, which terminate in a sharp point, and, like 

 those of the ant-lion, are perforated, serving the insect instead 

 of a mouth; for through this orifice the nutriment passes 

 down into the stomach. When amongst the Aphides, like 

 wolves in a sheep-fold, they make dreadful havoc: half a 

 minute suffices them to suck the largest ; and the individuals 

 of one species clothe themselves, like Hercules, with the 

 spoils of their hapless victims. 



Next in importance to these come the aphidivorous flies 



1 Reaum. vi. 282. St, Pierre's Voyage^ 72. 



2 Bartram in Philos. Trans, xlvi. 126. 



