Woolly aphids ?

Woolly aphids ?

Observation - Woolly aphids ?. Description: A twig of alder in the border between a thin strip of grassland and a pool was covered in fluff. After a while I noticed the fluff was moving. The only references to woolly aphids on alder I can find on the internet are from the other side of the Atlan

A twig of alder in the border between a thin strip of grassland and a pool was covered in fluff. After a while I noticed the fluff was moving.

The only references to woolly aphids on alder I can find on the internet are from the other side of the Atlantic and the species Prociphilus tessellatus.

Are aphids of this sort plant specific? Any suggestions as to the species?