INDIRECT BENEFITS DERIVED FROM INSHCTS. 151 
egs, The common sand-wasp (Ammophila vulgaris) destroys caterpillars 
of a larger size, and most of the other Vespoid and Sphecoid Hymeno- 
ptera, viz. Trypowylon, Philanthus, Larra, &e. assist in this great work. 
Pompilus, to which genus probably several species mentioned 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 (Sphew ceruleus), has been 
known to seize a spider eight times its own weight.1_ 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 cockroach, and is therefore one of the great benefactors to 
mankind. 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 
be 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 
Sphex pennsylvanica of Linné, 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 (Hemerobius), 
the larvae of which, Reaumur, from their being insatiable devourers of 
them, has named the lions of the Aphides. The singular pedunculated eggs 
from which these larva proceed, taba describe when we come to treat 
upon the eggs of insects; the larve themselves 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 (many species — 
of Synphid@), whose grubs are armed with a singular mandible, furnished 
like a trident with three points, with which they transfix their prey. They 
May often be seen laid at their ease under a leaf or upon a twig, environed 
by such hosts of Aphides, that they can deyour hundreds without changing 
their station; and their silly helpless prey, who are provided with no 
1 Nat. Hist. of Carolina, ii. 105. 
2 Reaum. vi. 282. St. Pierre’s Voyage, 72. 
5 Bartram in Philos. Trans. xlvi. 126. 
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