Looks like a Monarch egg to me! It's rare to see eggs on top of leaves, but not impossible. Just like humans, Monarchs are not perfect and will occasionally do things differently than expected, such as laying eggs on Dogbane by mistake, or in this case, laying them on top of leaves, where they are easier for predators to find.
Can't wait to see Monarch eggs here, but that's probably at least another month away. Don't usually see much Monarch activity until July. I definitely have more than enough Milkweed for them this year. My Common Milkweed is thriving. I wanted my other native species to grow and mature before the Common Milkweed started spreading, which would minimize the spreading, but too late for that! I also have a lot of second-year Orange Milkweed coming up! It's not a rhizome-spreading specie, which is nice. It grows where you plant it, and I planted a lot of it! It's hard to beat, with the bright orange color and the long blooming season. It'll look great this year and fantastic in another year or two!
Then I have Whorled Milkweed, which does spread by rhizome but has only spread a little since I added it. Probably not enough to attract many Monarchs, but it'll get there eventually. Of course, this year, I'm also working on adding more Swamp Milkweed. I had four plants last year, but I've grown some from seed and will be adding about 20 to 30 more as soon as the seedlings are big enough to plant.
I was
very disappointed that my Meadow Blazing Star rotted away this year. As some of you may or may not know, it's the #1 Monarch magnet, by far. They can't get enough of its nectar. I only had one plant, so this year, I won't have any blooming.
Luckily, I've seen four or five seedlings coming up, but I have my doubts that they'll make it through next Winter and Spring without rotting away, too. I'll have to figure something out, because no Monarch-friendly garden should be without it.