Insect has black eggs and at least one instar different from this photo, all stages are on same leaves at same time. I noticed it about 4 weeks ago. There are literally hundreds on a single plant. They suck on the plant, it yellows, goes brown, and dies. This happened to about 30 artemesia vulgaris, then 3 aster nove-belgii, then 2 ratibidia, and they are working on my last aster, 3 more ratibidia and I think are moving onto a solidago. All plants have been in the ground for 1-3 years already. I don't know how the insects spread; the ratibidia are behind a wooden wall on the other side of the driveway from the asters and artemesia.