In concluding this subject, it may not be superfluous to advert to an objection which is sometimes thrown out against regarding with any particular sympathy the affection of the lower animals to their young, on the ground that this feeling is in them the result of corporeal sensation only, and wholly different from that love which human parents feel for their offspring. It is true that the latter involves moral considerations which cannot have place in the brute creation; but it would puzzle such objectors to explain in what respect the affection which a mother feels for her new-born infant the moment it has seen the light, differs from that of an insect for its progeny. The affection of both is purely physical, and in each case springs from sensations interwoven by the Creator in the constitution of his creatures. If the parental love of the former is worthy of our tenderest sympathies, that of the latter cannot be undeserving of some portion of similar feeling.
I am, &c.
[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 vegetable 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 invites 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 nauseous 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. 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 fifth the fruit or seeds. Even still further selection takes place. Of those which feed upon the roots, stem, and branches, of vegetables, some larvæ eat only the bark (Sesia apiformis, &c.), others the alburnum (Semasia Wœberana), others the exuding resinous or other excretions (Scoparia Resinella), a third class the pith (Xanthia Ochraceago), and a fourth penetrate 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 veins (Aphides in all their states), others eat only the parenchyma, never touching the cuticle (subcutaneous Tineæ, Gracillaria?) others only the lower surface of the leaf (many Tortrices), while a fourth description devour the whole substance of the leaf (most Lepidoptera). And of the flower-feeders, while some eat the very petals (Cucullia Verbasci, Xylina Linariæ, &c.), others in their perfect state select the pollen which swells the anthers (bees, Lepturæ, and Mordellæ), and a still larger class of these the honey secreted in the nectaries (most of the Lepidoptera, Hymenoptera, and Diptera).
Nor are insects confined to vegetables in their recent or unmanufactured state. A beam of oak when it has supported the roof of a castle five hundred years, is as much to the taste of some, (Anobia,) as the same tree was in its growing state to that of others; another class (Ptini) would sooner feast on the herbarium of Brunfelsius, than on the greenest herbs that grow; and a third (Tineæ, Termites), to whom
"... a river and a sea
Are a dish of tea,
And a kingdom bread and butter,"