Beech Blight Aphid

I found a colony of a small, weird organism on a young beech tree as I was climbing up Starkey Hill near Guelph. Each individual was tufted white with one particular long white hair and it, bizarrely, waved back and forth from a brownish/black base. I guessed it was some kind of insect but it didn’t look like anything familiar. In fact, the waving back and forth reminded me more of a marine organism.
A naturalist friend of mine found a colleague to id it.