These are aphids on milkweed. The yellow ones, oleander aphid, are an invasive species.
The specific issue here is that monarch butterflies need milkweed. My former colleague Colin Purrington and many other monarch-loving folks have been encouraging people to plant swamp milkweed in order to help the butterflies out.
The oleander aphids aren’t a major menace compared to people simply clearing out milkweed when they should leave it alone, but if enough of them cluster on a plant, they’ll kill it. There are times walking around here when I see them in that density. I don’t think it’s worth it to try and kill them, unlike lanternflies—there are too many of them, and most of the ways you might try to remove them could hurt monarch eggs.
I have complicated feelings about the most over-the-top anti-invasive campaigns anyway. I’m glad to stomp lanternflies. If I could strip all the English ivy I see, I would, though that’s a brutally exhausting business. If you gave me a magic button that would destroy every emerald ash borer in existence, I might press it. Crusading against invasives takes a huge amount of effort, and really only succeeds when there’s a major investment of labor and resources, and only then for a time. The Anthropocene is a fitness landscape that makes a globalized ecology all but inevitable.
And there’s a tinge in some anti-invasive campaigns of a nativism that’s too close for comfort to human ideologies. Some invasives establish themselves so thoroughly that it’s impossible to think how you’d get rid of them, and some of them aren’t that different in their ecological fit than an existing species.
One of the great pleasures of macro photography for me is getting to see things in the world that I can’t perceive as clearly or with as much detail with my own eyes. The images aren’t quite microscopic, and that’s for the best: a macro image is still recognizable in relationship to what the naked eye saw as opposed to being something wholly unperceived by our vision.
When the weather warms this spring, I’ll probably try to do a whole-day macro shoot in one of several nearby fields. Given what a warm winter it’s been, I’ll certainly have to be wearing a full outfit that’s been soaked in permethrin and have repellant all over any exposed part of my body, and even at that, I’m nearly guaranteed to come home with ticks on me. (Oddly enough, I’ve never actually seen a dog tick on a plant even though I know they are there. Deer ticks are too small to see a lot of the time even after they’re on your body.)
I’d do this sort of thing more often but for that issue—having had Lyme once, I’m in no hurry to get it again. Ticks, in any event, aren’t invasives. (Except for the new longhorned one that’s been spotted around here lately. Sigh.) They come with the territory.