in zoology, a genus of insects belonging to the order of insects hemiptera. The rostrum or beak of the aphis is inflected; the antennæ or feelers are longer than the thorax; it has four erect wings; the feet are of the ambulatory kind; and the belly often ends in two horns. There are 33 species of the aphis, all of which are inhabitants of particular plants; and from this circumstance their trivial names are taken; as aphis ribis, ulmi, roseae, &c.