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The Aphis

THIS is an insect which has engaged the attention of naturalists for various reasons: their generation is equivocal, and their instinctive economy differs, in some respects, from that of most other animals. Linnæus defines the generic character of the aphis thus: beak inflected, sheath of five articulations, with a single bristle; antennæ setaceous, and longer than the thorax; either four erect wings, or none; feet formed for walking; posterior part of the abdomen usually furnished with two little horns. Geoffrey says, the aphides have two beaks, one of which is seated in the breast, the other in the head; this last extends to, and is laid upon, the base of the pectoral one, and serves, as that writer imagines, to convey to the head a part of that nourishment which the insect takes or sucks in by means of the pectoral beak.

Gmelin enumerates about seventy species, all of which, and doubtless many others, are found in different parts of Europe. They infest an endless variety of plants; and it is believed that each species is particularly attached to one kind of vegetable only: hence each sort has been hitherto named after the individual species or genus of plants on which it feeds; or if that could not be ascertained, that on which it had been found; for some species are rather uncommon and little known, though others are infinitely too numerous. The aphides are sufficiently known by the indiscriminate term of plant-lice; they abound with a sweet and grateful moisture, and are therefore eagerly devoured by ants, the larvæ coccinellæ, and many other creatures, or they would become, very probably, more destructive to the whole vegetable creation than any other race of insects known. If Bonnet was not the first naturalist (as is generally acknowledged) who discovered the mysterious course of generation in the aphides, or, as he calls them, pucerons, his experiments, together with those of his countryman, Trembley, tended at least to confirm, in a most satisfactory manner, the almost incredible circumstances respecting it, that an aphis, or puceron, brought up in the most perfect solitude from the mo ment of its birth, in a few days will be found in the midst of a numerous family; and that if the experiment be again repeated on one of the individuals of this family, a second generation will multiply like its parent; and the like experiment may be many times repeated with the same effect.