Monday, June 6, 2011

Spider Milkweed

Spider Milkweed, Asclepias viridis, is my favorite of the milkweeds at Blue Jay Barrens. The flower head is both showy and not showy. The lime green corolla lobes are conspicuous from a distance, which is considered to be showy. However, that color makes you think of a sickly, poorly performing plant, which is a failure as far as producing the attractive side of showiness.

This is one of those southern plants that reaches its northern limits in Southern Ohio. The population here has been increasing slowly over the past 20 years. I don’t think it’s in danger of dieing out, even though a few plants turn up missing every time we have a particularly cold winter.

It makes its home in the prairie openings. Full sun and dry conditions seem to best suit its needs. It also seems to do best in areas with minimal tall grass. I haven’t found any of these milkweeds growing in the thick Indian Grass, or Big Bluestem areas.

Flowering stalks are usually around 18 inches tall. Without the flower, they blend neatly with the other vegetation and are hardly noticeable. The lean is typical. I rarely find any flowering stalks that are completely vertical.

Ants are the only insects that I see regularly visiting the Spider Milkweed flowers. It’s odd that other milkweed species are so attractive to bees, butterflies and flies, but none of those fliers visits the Spider Milkweed. Ants may be the prime pollinator for this plant.

I found these larvae munching away on the corolla lobes. I didn’t have much luck with a positive ID, possibly because these guys are still so young.

I’ll give the larvae a few days to put on some size and then take another look at them. I just hope I can find them again later. It seems common for young larvae to begin life by eating the more tender parts of the plant, such as the buds or flowers. As they get larger, they move on to the leaves. If I have my typical luck, I’ll find nothing when I go back. We’ll see.


  1. I suspect the caterpillars are early instar milkweed tussock moth (Euchaetes egle). I'll be anxious to see how they turn out.

  2. You're probably right, Ted. But as long as I'm unsure, I'd rather imagine it's going to be something rare.

  3. Very cool, i'm not as familiar with the flower structure of this species, however if it is as other asclepiads i would think you would need someone larger than an ant to transport the pollinium to another colony plant and have it placed in range of the stigmatic slit!

  4. Hi, Michael. I agree that it seems unlikely that an ant could accomplish the task, especially since it always seems to be tiny species that visit these flowers. I just never see any other likely suspects around the flowers. It's also possible that some night flying moth or beetle is responsible. If there were 20 of me, I would assign a few of my selves to investigate things like this.

  5. lol..I hear about a game camera on a pole? really really close! I don't even know if a bee would set off a game camera?