PlantFiles is getting a new look! Just in time for spring, we're rolling out a new look for the best online plants database. It will also work with your smart phones and mobile devices, so now you can take it with you on garden center visits or botanical garden tours. Questions or comments? Please post them here.
Unfortunately, I cannot see enough detail in your images to be at all confident of an i.d. - could you try borrowing a camera with better macro capabilities? One possibility is aphids, but it is a bit late in the year (especially at your latitude) for these to be a problem. Nevertheless, you might try Googling images of aphids/plant lice to see if anything resembling your critters pops up.