I don't know why wasps kill caterpillars, but they've been doing it probably longer than there have been humans walking the earth. If we didn't have wasps, we might be overrun with so many caterpillars, we'd think they were pests. If you want to keep the caterpillars from being victims of the wasps, you need to bring them in or enclose them with fine mesh that will keep the wasps out. You can buy special sleeves that slip over a plant or tree branch to keep the developing cats safe. Many of us on this forum enjoy bringing cats indoors or onto a porch and keeping them supplied with fresh host plant while they grow inside protected containers. That way, you get to see them when they come out of their chrysalis and might even be able to breed some in captivity. Then you could raise even more. Good luck finding a way to protect them. I hope your illness resolves or remisses soon.

Martha

Some wasps use caterpillars as food for their own larvae, either laying eggs on the caterpillar but leaving the caterpillar where it is, or paralyzing the caterpillar and then laying the eggs on or in the paralyzed caterpillar which is placed in whatever shelter the adult wasp constructs for the young. Docmom has given two great suggestions for protecting your caterpillars, or you could probably put hoops over a part of the bed to protect it and move caterpillars there as you find them. I use a narrow plastic plumbing pipe (ADS - black & comes in a coil) with the ends sunk about 8" and covered with netting. Alternatively, you could use EMT metal electrical conduit and use right angle connectors to create U's to stretch your netting over.

I use an electric tennis racket to stop wasps from searching my nettles for RA cats.

If you are going to use those kinds of traps, set them up far away from your hostplants.

Slowly walk your property and look for wasp nests. Watching where wasps go is the best bet since many nests are hidden. Spray the nest opening at night.

Most caterpillars are not going to make it unless you somehow protect them. Or you could raise gypsy moths. ;)

If you were gone for two weeks, chances are that the caterpillars pupated if they were still living. Birds eat caterpillars too.

I hate to see the wasps too, parasitic and otherwise, but they also help to control other caterpillars too like DocMom said. Those other caterpillars which can eat many things might destroy the host plants that you've installed for the desirable butterflies. All in balance.

Some non-native wasps have been released to control agricultural pests, but then also parasitize non-target larvae. And that really irks me.

Anyway, I see my yard as a small sort-of functioning ecological system, and there is a system of balances and checks. The caterpillars that do survive may be more "fit" if they were able to evade the wasp.

The plants themselves release odors (volatile organic compounds) into the air which attracts predators to help the plant out.

If you grow food for yourself, you might want to have these biological controls around too.

As others have mentioned, if you want to make sure they make it to adulthood, bring some in to raise. Only 1% of the eggs laid by a butterfly make it to adulthood, which is why they lay so many eggs.

Hopefully, your caterpillars are safe somewhere in their chrysalides, but those can also make a meal for different animals.