APHIS (a'fis), a genus of insects, the typical one of the family aphidu. It contains those soft pulpy little animals, winged or wingless, and with long anten na;, which are seen beneath the leaves, or in curled-up leaves, or in the axils of many plants, or even on the roots of some. Sometimes, as in the case of the elm, their destructive operations upon a leaf raise a gall of considerable size. The species are very numerous, and are called after the plants on which they feed, as A. rosx, the aphis of the rose; A. fabie, the bean aphis; A. brassicm, the cabbage fly; A. humuli, the hopfly. They are exceedingly prolific, but are kept within bounds by various insects, especially by the coccinellide, or lady birds, of which they are the ap propriate food. They drop a fluid called honey-dew, which is so grateful tothe ants that the latter, to receive it, tend them like milch cows. The mode of propa
gating their race is the abnormal one described as alternation of generations, metagenesis, and parthenogenesis. The winged aphides, confessedly perfect in sects, bring forth a wingless race, apparently mere larva?, and which there fore, it might be thought, would be in capable, while thus immature, of bring ing forth young. In certain cases they do it, however, and their offspring are winged, and as perfect as their grand parents. This alternation of genera tions, or metagenesis, with its attendant parthenogenesis (or birth from virgins) in every second generation, goes on for nine or ten generations by which time the season is over. The last aphides of the year are fully formed and winged, and deposit eggs, which are hatched in spring.