Aphids are true bugs - they feed on plant sap which they suck up through highly modified very thin tubular mouthparts called stylets.
Euceraphis betulae belongs to a subfamily of aphids - the Calaphidinae. They live on the leaves of deciduous trees.
It belongs to a tribe, called Calaphidini. Aphids in this tribe restrict their feeding to trees in the family Betulaceae, which includes alders (Alnus) and birches (Betula).
Aphids of the genus Euceraphis are very particular about the trees they colonise - each species restricts its feeding to one birch species.
E. betulae lives only on the silver birch, Betula pendula.
In Britain there is a second common native birch species - the downy birch Betula pubescens, which is closely related to the silver birch but tends to occur in damper soils and is more common in north and west Britain.
The downy birch is colonised by a different, very closely-related Euceraphis species, E. punctipennis.
E. betulae and E. punctipennis are very difficult to tell apart and for many years were not recognised as separate species.
Differences in their chromosomes help distinguish them.
E. betulae has 2 pairs of the chromosomes called autosomes (A1 and A 2), whereas in E. punctipennis these have fused into one long pair (A).
In North America and eastern Asia other Euceraphis species live on birches and alders native to those regions.
In Europe there are 12 other aphid species that feed on birch trees - most of them are in the same aphid subfamily as Euceraphis. However, Euceraphis is recognisable by a combination of the following: