Aphids are sap-sucking true bugs. They range in size from 1 to 7 mm (¼ in or less) long. Some aphids are known as greenfly or blackfly, but there are species that are yellow, pink, white or mottled. There are more than 500 aphid species in Britain. Some feed on only one or two plant species, but others can be found on a wide range of plant hosts. Many have lifecycles that involve more than one host plant. Almost any plant can be a host to aphids, including ornamentals, vegetables, fruits, greenhouse plants and houseplants. More information on aphids. 

Hellebore aphid is whitish green and only found on hellebores it is present throughout the year, although colonies are usually only noticed in spring.
 

• Whitish-green aphids, 2-4 mm (about 1/8 in) long, sometimes form dense colonies on the underside of hellebore leaves and flowers in early spring
• The sugary honeydew they excrete can lead to the growth of sooty moulds on the foliage
• This species of aphid is only found on hellebores

Aphids form the basis of many food chains and it is not unusual to have some of these animals in a healthy balanced garden ecosystem. On established plants, aphids can be considered part of the biodiversity they support; natural enemies will normally reduce numbers before summer.

• Where possible tolerate populations of aphids
• Check hellebores frequently from spring onwards so action can be taken before a damaging population has developed
• Use finger and thumb to squash aphid colonies where practical
• Encourage aphid predators in the garden, such as ladybirds, ground beetles, hoverflies, parasitoid wasps and earwigs. Be aware that in spring aphid populations often build up before natural enemies are active in sufficient numbers and then give good control