The only way I know of for sure is to bring them and raise them yourself, but it doesn't sound like you have the time. I have a willow tree (small) growing in a container (large) and I covered it with bridal veil material to keep the wasps off, but I found a wasp inside it anyway - somehow it slipped in! :( So I took the cats in and raised them myself. Beyond this, I don't have an answer - maybe somebody else will.

Sherry

Sambac,
Nature does seem cruel, but that wasp is just trying to survive just like the butterflies we all love. As much as we wish we could, we can't all drop everything to take care of our caterpillars. Sometimes the best you can do is to provide the appropriate circumstances (a garden full of chemical-free plants) and hope some make it. Know that your garden is as close to a haven as we can give them, and if everyone would care as much as you do, the butterflies wouldn't be threatened as they are. I'm sorry for your frustration.

Martha

Not sure what type of wasps you have, but at times you can find their nests. The ones that most often visit my garden are a kind or kinds of paper wasps. They most often create nests in my pipevines. When I see them coming out of the vines I look to see if I can spot the nest, if not, I poke around with a rake. When I know where the nest or nests are I spray them with this wasp spray that allows you to spray from about eight feet away. This eliminates the nest and most of the wasps in it.

You can purchase the wasp sprays in many stores.

Yellow Jackets are more dangerous, because they make nests in the ground and are very aggressive, but they can be dealt with in the same manner.

Here is a link that might be useful: Paper wasps

I'm with Docmom on this one...
If you plant your host plants amongst other non host plants, the cats can hide in them during the day and feed at night. Queens love Whitevine, a native to South Florida. This will grow easily thru a hedge s taking over. It loves poor rocky soil and has some salt tolerance.
Also, the more host plant you have, the more larvae, and hence some inevitably make it thru to adulthood.
Monarchs and Tropic Queens also love Whitevine.

Yes the host plants are amidst other plants, in fact all similar host plants planted in clumps to give it density and thickness. Yes, these wasp look large, aggressive and pretty quick.
Great idea to look for the nest, will do that. And also a quick growing vine like white vine is a great idea, as these catts have nothing left of my passiflora, and they chomp away all tender new growths as well. lol

I know what you mean, a few years back I was in my garden looking for either eggs or cats when I saw this wasp had found one before I did. One year I also witnessed the same kind of wasp attack and start stinging a full grown Monarch butterfly, I was able to pin them down while they were fighting and kill the wasp. Surprisingly after a couple a minutes the Monarch seemed good as new and was able fly away. I think these type of wasps that I've seen are called Mahogany wasps and they are very aggressive especially around their nests. I love nature but will kill these wasps whenever given the chance. When I first started my butterfly garden in 2000 I would leave any cats I found outside on the host plants but it never failed that within a day or two they would be gone and I rarely ever found a chrysalis so that's when I started raising all that I found inside. In my own estimates I figure maybe only 10% of all eggs make it to become a mature butterfly but when I bring them in and raise them about 90% + do.

Leave them be. Anytime mankind jacks with the natural order of things, it messes up the balance of nature.

Deanna

Amen, Deanna. If anything, these nests could be jetted down c a garden hose only, no chems needed Yellowjackets I wouldn't mess with at all. I raise all my high risk cats indoors and release them and the end of their 5th instar.
This gives them a leg, or wing up on things.

I know, you don't want to disturb nature's cycle. But wasps behavior looks freaking atrocious, lol We have a large preserve behind our yard and god knows where they are nested, don't find any in my yard that I can go after.

Yesterday I had a huge number of cats on my butterfly bush.This morning when I walked down the yard to check them out I thought "wow! They grew huge over night!"
Just then, a red wasp moved in and stung the heck out of one of the inch-long cats....I tried to separate them but failed. *heavy sigh!
I found many, many more dead all over the place.
This just breaks my heart.