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LETTER XII. 
ON THE FOOD OF INSECTS. 
‘Insects, like other animals, draw their food from the vegetable and animal 
kingdoms: but a very slight survey will suffice to show that they enjoy a 
range over far more extensive territories. 
To begin with the vege/able kingdom.—Of this vast field the larger 
animals are confined to a comparatively small portion. Of the thousands 
of plants which clothe the face of the earth, when we have separated the 
grasses and a trifling number of herbs and shrubs, the rest are disgusting 
to them, if not absolute poisons. But how infinitely more plenteous is 
the feast to which Flora inyites the insect tribes! From the gigantic 
‘banyan which covers acres with its shade, to the tiny fungus scarcely visible 
to the naked eye, the vegetable creation is one vast banquet at which her 
insect guests sit down. Perhaps not a single plant exists which does not 
afford a delicious food to some insect, not excluding even those most nau- 
seous and poisonous to other animals,—the acrid euphorbias, and the 
lurid henbane and nightshade. Nor is it a presumptuous supposition, that 
a considerable proportion of these vegetables were created expressly for 
their entertainment and support. The common nettle is of little use either 
to mankind or the larger animals ; but you will not doubt its importance 
to the class of insects, when told that at least thirty distinct species feed 
upon it; and however important the oak may be to us, it is still more so 
to the insect world, of which Résel calculated that two hundred species 
either feed upon it, or upon other insects which do. But this is not all. 
The larger herbivorous animals are confined to a foliaceous or farinaceous 
diet. They can subsist on no other part of a plant than its leaves and 
seeds, either in a recent or dried state, with the addition sometimes of the 
tender twigs or bark. Not so the insect race, to different tribes of which 
every part of a plant supplies appropriate food. Some attack its roots; 
others select the trunk and branches; a third class feed upon the leaves; 
a fourth, with yet more delicate appetite, prefer the flowers; and a filth 
the fruit or seeds. Even still further selection takes place. Of those 
which feed upon the roots, stem, and branches of vegetables, some 
larvae eat only the bark; others both the inner bark and alburnum (Sco- 
tytus, &e.); others the exuding resinous or other excretions (Orthotenia 
resinella); a third class the pith (Aigeria tipuliformis) ; and a fourth pe- 
netrate into the heart of the solid wood (Prionus, Lamia, Cerambyx, &c.). 
Of those which prefer the leaves, some taste nothing but the sap which 
fills their yeins (Aphides in all their states); others eat only the paren- 
chyma, never touching the cuticle (subcutaneous Tinee) ; others only the 
lower surface of the leaf (many Tortrices) ; while a fourth descrijtion de- 
vour the whole substance of the leaf (most Lepidoptera). And of the flower- 
