I don't know beans about ants, but I do know that raising ALs is hard, probably harder for you, since they're on what I think is a low growing plant.
Watching adult ALs here, I only see them laying eggs on the flower heads when the cudweed has started to bloom or is about to - I've never found an egg on a leaf. By that time, the plant has gotten big enough that if you cut at least 6" or so down on the stem, you can put it in a water pick or other such water-filled thing, and the plant will stay fresh for a long time. Still, I've found it's best to wait until the cats have grown to at least the ?second instar before bringing them in to raise. American ladies lay SO many eggs, that there are nests on nearly every cudweed plant on my property - of course, some are abandoned nests that the cats have outgrown.
There's no way you can keep the kind of fleshy new growth I think you're talking about fresh for any length of time, and if they haven't bloomed, the eggs/hatchlings really don't have a good hiding place.
Have you thought about planting some in containers that can be covered after eggs have been laid on them? What about using cudweed/Gnaphalium pensylvanicum? Does that grow in your area? It would be better to have a host plant that blooms early.
This is a difficult problem, difficult even with G. pensylvanicum. I'm sure many are lost here, because predators manage to get into the nests before I bring them in. Still, they lay so many eggs, many adults do emerge. I've got 6 chrysalides in my cages, and it appears that many of the outside ones made it to pupation on their on.
Some cudweed came up in a container that was in a gizmo made for vines - I covered it with mesh material -
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Sherry

Jeff, I don't know much about ants, so I can't tell you about the one in your picture, but I can tell you my experiences with raising American Ladies on pussytoes. I have a bed of them about 5' x 30' and get lots of cats. I never looked for eggs, but I always have lots of cats. The best time to find them is towards evening when they come out of their nests to eat (they love crawling up the flower stems and eating the flowers). I don't bring the tiny cats in but wait until they're a little bigger. I'm not going to go digging cats out of their nests; I only bring them in if they're outside of a nest at the time that I'm looking for them on the pussytoes.

The first year I wanted to raise ALs is when I discovered that it's virtually impossible to just take the leaves and put them in water because there's really no stem to them. That's when I decided that the only way I could raise them is to dig pieces of the plants out and plant them in pots. I use pots that are 9-10" wide and 5" deep and go around the outside of the plants and find whatever "runners" that I can. I guess you know from having the plants yourself how you can find root hairs hanging down from the plant. I keep putting pieces in a pot until it's full of them (I packed them in pretty tight even though it's a little tricky to do with the roots kind of off to the side of each piece/leaf bunch). I water them and let them drain. I can fit 3 of those pots inside each storage container that I have; I have the top of each screened.

Then I gather the cats, taking the leaf that each is on and lay them in the pots on top of the pussytoes that I have potted up and each can crawl onto the potted plants when they feel like it. Since the cats seem to skeletonize (right word?) the plants so fast, I only put a couple of cats in each pot, so I can't really raise too many cats. By the time the cats are done using the plants, they're pretty much useless to any other cats, so I really only raise about a dozen or so cats each year.

I have also considered building some kind of protective screen over the plants, but of course, I suppose insects could crawl in anyway; it's not like it would be a fortress that nothing can enter. I don't know how else to do it but to get some boards, like maybe 1x8's, 10's or 12's (depending how high you think it should be), screw/glue them together to form a rectangle, and then staple screening (I like the fiberglass mesh rolls of screen) onto the one edge of the boards. Then put the contraption over the plants like the Superdome. lol Of course, after cats have started pupating, you'd have to start checking it every day at some point and see if any have eclosed and let them out. If you didn't want to do that, you could remove each pupa after it's hardened and bring it inside.

Those are the only ideas I could come up with so far. I hope it helps you. Maybe someone else has some other ways that they raise them. Maybe on other kinds of plants it would be easier to raise American Ladies, but it's kind of tricky and takes more time with pussytoes, I think. I do love the plants though. Now that I have plants already in pots from last year, it's not like I have to spend time digging parts of the pussytoes plants out of the ground anymore unless I'd want to put more in other pots and get another storage container or just keep putting in replacement pots in the containers as the cats eat them up and then raise more cats. Oh, and I just let the potted pussytoes sit outside over the winter here (and I'm in PA) and they're fine the next spring. You could either let them outside for the ALs to lay eggs on them or put them where they can't get to them and bring in the ones that show up on the plants that are outside and put them on your potted plants.
Cathy

Cathy, that's very helpful. Thank you! What I ended up doing was taking about 3" of each plant -- enough to get some stems + root hairs -- and sticking them in a pot with loose, wet soil. The hope is that they'll root and grow. We'll see. Anything is better than ant-food.

Jeff

Jeff, I'm glad that the info helps you. What you said is what I do. I didn't know if any of the plant that I did out is considered stem or not so I didn't name call any of it stems, but maybe it is. I guess to me it just didn't seem like it. Ha. It's just that there seems to be so little there to work with that I just consider it all roots, but you're probably right and it's actually stem, but with root hairs or mostly. I'm sure yours will root if you got enough root hairs (what's enough, I can't explain :) with the piece of plant. Good luck and yes, better than ant food.
Cathy