APHIS, a genus of insects belonging to the order hemiptera, sub-order homoptera the type of a family called aphidii. They are small insects, living by sucking the juices of plants, upon which they may be seen congregated in immense numbers, often doing serious injury, causing the distortion of leaves, and even the blight and decay of the plant. The woolly aphis, or American blight (A. lanigera; eriosoma mali. of Leach), is sometimes very injurious to apple-trees, and when once it has found its way into a garden or orchard, is very difficult of removal. It is a minute insect, "covered with a long cotton-like wool, transpiring front the pores of its body"—"a cottony excretion"— in which it differs from the ordinary aphides, and takes its place in the chinks and rugosities of the bark, multiplying rapidly, extracting the sap, causing diseased excres cences; and, ultimately, the destruction of the tree. It was first observed in England in 1787; but it is uncertain if it was, as has been supposed, accidentally imported from America. The hop-fly (A. huntull), and the A. of the turnip and cabbage (A. brassica), have sometimes caused the destruction of entire crops. The price of hops varies front one year to another, very much according to the numbers in which " the fly" has appeared. The potato A. (A. rastator) has been represented as the cause of the potato disease; but this opinion has few supporters. The aphides of the rose (A. roses) and of the bean (A. faba) are among the most familiarly known. Every one must have observed the leaves of trees anti shrubs deformed by red convexities. In the hollows of the under side of these, aphides have their habitation, and there they find their food; the exhausted leaf at last curls up. Most of the species are green; the A. of the bean is black. They
are generally called plant-lice. They have a proboscis (haustellam), by which they pierce and stick plants; and at the extremity of the abdomen, two horn-like processes, front which exude frequent small drops of a saccharine fluid called honey-dew, a favorite food of ants. It has been seen even to fall in a kind of shower from trees much covered with aphides. Mention has been made in the article ANT, of the means which ants take to obtain this food. The leg-s of aphides are long, and they move slowly and awkwardly by them. The greater number of them never have wings; it is in the autumn that per fect winged insects generally appear. From the pairing of these result eggs, which pro duce female aphides in the following spring, and successive generations of wingless aphides are produced in a viviparous manner without impregnation throughout the summer, after which winged aphides again appear. Their increase is restrained not only by birds, but by insects which feed on them. A family of coleopterans insects, to which the genus eoceinella or lady-bird (q.v.) belongs, has received upon this account the name of aphidiphagi, or aphis-eaters. There are also certain minute hymenopterous insects, which destroy them in great numbers by depositing their eggs in them; the larva feeds upon the living A., out of which it at last eats its way, leaving a mere desic cated skin.