"Macrosiphum hellebori", commonly known as Hellebore aphid or greenfly, is a sap feeding aphid that infests the flowers and foliage of hellebore plants. The whitish-green aphids are about 2–4mm long and form dense colonies on hellebores, coating them with a honeydew that can lead to the growth of sooty mold on the leaves and flowers of the hellebore. This species of aphid only affects hellebores and is most active in March and April when the hellebores are flowering and when few aphid predators are around, though they may infest during any time of the year.