Apparently there is interest in recent years in locating Lipaphis alliariae in the US, where it is not widely observed. The species is partial to Garlic Mustard, The species has a shell with a "grenade" appearance, and at maturity has a dark green, almost black colour. There are also more common species e,g Turnip Aphid, which also has a similar appearance but a lighter colour. The photos here appear to show two or three different species on Garlic Mustard, with the predominent curling of stems. There are also photos of Winged Lipaphis. Those of you who are more expert might be able to discern the difference in species. The "grenade" appearance seems obvious on some of the specimens. Not all photos are of the same Garlic Mustard plant. There is a section along the trail where I walk where there are several GM's over approx 100 yards.