The pernicious ravages of the aphis, however, are checked by its natural enemies. Fortunately it has many of these in other insects. Helpless and inactive of itself, it is equally incapable of shunning danger by flight, and of repelling it by force. Wings almost seem superfluous, they are so seldom used by the few which are provided with them. The coecinella, a small he mispherical beetle, well known by its trivial name, the Zady bird, chiefly lives on aphides, both while alary a or worm, and after attaining its perfect state. Ano ther dreaded enemy is the ichneumon Ily, which ope rates destruction in a more extraorciinary way. The female, which is often to be found where aphides are plenty, selects one suitable to the object it has in view, not of serving as food to itself, but as a nidus and ali ment to its young. By means of a sharp instrument, proceeding from the abdomen, said to be invisible to the naked eye, it punctures the body of the aphis, and deposits an egg within it. A single aphis is not enough; several arc, in the same manner, successively punctur ed, and each receives an egg. The egg is quickly hatched, when the young larva proceeding from it lite rally devours the aphis alive. Having consumed the whole, excepting the skin, the larva first becomes a chrysalis, and next attains the perfect state. It then flies away to inflict a similar wound, for the purpose of preserving its progeny. Different aphides are infested by different ichneumons ; and though generally sub mitting to this lethal operation patiently and without resistance, some occasionally seem to anticipate the danger, and strive to shun so mortal an enemy. Be
sides the coccinellx and ichneumons, the larva of a species of fly, thence called 771US•U aphidivora, feeds vo raciously on aphides. Twenty or thirty scarcely suffice for a meal. The earwig likewise contributes to their destruction, and many are devoured by birds. At the latter end of the season they appear infected by disease ; their bodies swell and discolour; gradually weakening, they lose their hold, hanging by the proboscis only, which still remains inserted ; and at length they drop ofl and disappear. The extraordinary multiplication of these animals is, therefore, counterbalanced by the dan gers to which they are exposed ; and their destructive ravages are checked by the numerous enemies to which they become a necessary prey.
SEE Bonnet, Sur les Pucerons, Mite d'Insectologie et CEuvres, tom. 1. De Geer, Armoires Sur les In sectes, torn. S. Lyonnet, Theologie des Insectes de Les ser. Geoffroy, Armoires sur les Insectes, tom. 1. Lin nxus, Fauna Suecica. P. Huber, Relations des Fourmis avec les Pucerons et les Galle Insectes. Reaumu•, Me moires sur les Insectes, torn. 3, 6. Richardson On the .41zhides of Linn.cits, Phil. Trans. v. 61. Curtis On :Wicks, Transact. Linnican Society, vol 6. (c)