I have a Chokecherry tree that has lots of aphids, I also have a lot of attached insects. I looked on your page: http://www.ext.colostate.edu/pubs/insect/05550.html and I was wondering if this is a variation of the lady bug larva in figure 2?
Denver County Colorado trees and shrubs
Those larva look like the larva for the multicolored Asian lady beetle. Here is a great fact sheet about all things lady beetle.
It is great to know that the lady beetles are helping you control your aphid problem.
I hope this helps.
Thank you very much!