Whether the aphids ultimately kill the sunflower remains to be seen, but for now they have probably provided fodder for all kinds of predators such as those goldfinches. They'll stay, and if some enemies rise up against them and wipe out the colony, so be it.
RIGHT HERE). My initial reaction was that they were one of the milkweed bugs, and I guess they are, sort of. While false milkweed bugs occur on milkweed plants, they routinely jump ship and feed on plants in the sunflower family.
I'm sure this one sunflower plant spawns plenty of other action that I didn't see in my limited observation time. It certainly created a bit of intellectual stimulation between passing the fifteen feet from my car door to the house's front door. Even just a few native plants can cause a massive boost in biodiversity. You would never see this sort of action on a hosta or most other alien garden fare.
And that's just the front yard, which has to be kept rather tidy and groomed for appearance's sake. Wait'll you see the far wilder backyard!
Again, if you wish to delve more deeply into the world of native plants and their myriad benefits, visit the Midwest Native Plant Conference.