Despite having a lot of their favorite host plant (swamp milkweed) in my backyard, I have only seen the milkweed leaf beetle (Labidomera clivicollis) a few times.
Milkweed leaf beetles are vegetarian — they prefer the leaves and flowers of just about any milkweed species. Their bold black and orange coloration warns predators to stay away from a potentially poisonous meal, but these beetles don’t sequester the toxic milkweed chemicals like the monarch caterpillars do.
This is the only species of milkweed leaf beetle found north of Mexico, and is apparently pretty rare throughout some of its range. Surprising, since its close relative, the Colorado Potato Beetle is a real pest. But one researcher found that the larvae of this beetle are highly vulnerable to predation when they occur on milkweed species growing in an old field or prairie where the vegetation is continuous. They survive much better on swamp milkweed where the plants might be surrounded by a moat of water, a barrier to the roaming predators. Well then, welcome to my garden.
The one beetle I found in the morning acquired a friend by the evening. I imagine it’s difficult to stay affixed to a large, spherically shaped, slick, waxy object when your legs are too short to get a good hold. The male continually tapped the female’s back with his antennae while trying to jockey himself into position.
“Slip-slidin’ away…You know the nearer your destination, the more you slip sliding away.” Paul Simon’s lyrics seem appropriate for this couple.
Back Yard Biology 
Wonderful macro shots, Sue. You must be loving that new lens in situations like this. You were able to capture an amazing amount of detail, especially considering that the subjects were not exactly sitting still.
Thanks, Mike. Yes, I am definitely enjoying the new lens. The male was moving around quite a bit trying to get in position, but the female sat rock still. However, there was too much difference in their position to get them both in focus at once, so I opted for some middle ground.
I might have mistaken these guys for ladybugs on a glance. We have plenty of milkweed along the irrigation ditch and down by the river and pond.
They are quite large — the photo probably doesn’t show that accurately. They might be at least twice as big as a ladybird beetle.
Those are good shots. I really like the back pattern in the first one.
Thanks, Lyle. I learned that the black pattern on the back is highly variable between individuals, so I guess one could learn to recognize them.
Excellent macros. I wish I could grow swamp milkweed here. It’s a beautiful plant but very hard to find here.
Thanks, I am loving this macrophotography gig. The swamp milkweed plants itself all over my yard, so I am constantly pulling it out. I love the way it attracts all the insects, but I don’t love the number of seeds it produces!