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Any of various small, soft-bodied insects of the superfamily Aphidoidea that feed by sucking sap from plants and that can reproduce asexually. Also called plant louse.
[New Latin Aphis, Aphid-, type genus, coined by Carolus Linnaeus, perhaps as a back-formed singular *Aphīs, from plural *Aphīdes, irregularly derived from Greek apheideis, plural of apheidēs, unsparing, unmerciful, lavish (in reference to the damage caused by aphids or to their high reproductive rate) : a-, not; see a-1 + pheidesthai, to spare, be merciful, live thriftily; see bheid- in Indo-European roots.]
a·phid′i·an (ə-fĭd′ē-ən) adj. & n.