I was in my garden late the other night seeing if there were any moths were about. I took this photo with flash of a siver y moth and did not notice the insects on the stem of the knapweed plant until I got the photo on the computer. This raises a few questions? What are they, have they just hatched and being guarded by their parents. I don't think they are being predated by the bigger ones. What are they doing two foot up a knapweed plant. maybe they have hatched in the flower head? I looked the next night and there was nothing to see. Any idea's? Thanks.
Looks like they could be Large Knapweed Aphid,a type of greenfly, probably gives birth to live young and sucks sap out of the plant stem.
Thanks Mike, I think you are right, aphid did not come to mind because of the size of them. My knapweed plants have supported lots of things this summer so I don't mind them having a bit of it. It's nearly done anyway and they will likely be food for other things as well.