Any of various small, soft-bodied insects of the family Aphididae which have mouth parts especially adapted for piercing and feeding by pulling the sap from vegetation: Aphids are plant lice which suck the sap from the stems and leaves of various plants and they develop wings and migrate to other places; especially, when there are too many of them in the area.

As small as they are, plant lice are big pests of many fruit trees and vegetable crops.