Euceraphis betulae on Silver birch (Betula pendula).
Suonenjoki, Finland.

Preference of this aphid species (and some other birch aphids) on yellow
senescencing birch leaves has been demonstrated in California
(Hajek, A.E., Dahlsten, D.L. 1986. Coexistence of three
species of leaf-feeding aphids (Homoptera) on Betula pendula
Oecologia 68, 380- 386) and
in Finland (see Oikos 99: 184-188. and
BioEssays 30: 889-896.).