How to spare Black Swallowtail caterpillars and still save my dill

First-year gardener here.  I planted everything late but got a reasonable crop of most things.  The dill did especially well until the attack of the Black Swallowtail caterpillars. They pretty much destroyed the smallish crop and then I pretty much destroyed them.  Now that I know what they are, I think I'll be growing dill for them and buying dill for me (or growing some indoors). If there was one caterpillar, there were 50.

I think the butterflies are probably good for the environment and they are pretty so I don't want to kill the caterpillars, but is there a way to control them?  I can only think to plant way more than I need and then pick them off the plants I want to harvest but let them run wild on the plants I've designated for them.  Maybe I can talk to them and ask them to only eat certain dill plants?

Any advice is welcome.

Netting half your dill may produce the result you want.

You could also put in some low-care perennials they like, like fennel, parsley or rue plants.  They love all those, too.  Rue and fennel require very little water, as well.

Then net the dill, like suggested above, or move the caterpillars to the other plants.  Ours were loaded this year!  The fennel is just now growing back.

It may not be so effective in a big caterpillar year, but I succession sow dill all over my gardens.   It's so easy to grow and self seeds too,  I usually have a younger patch just coming up if another patch succumbs to something.  Every couple weeks I toss down some more seed somewhere.  

I didn't know that is the butterfly they turn into. Must be why we have so many of both. I enjoy seeing the caterpillars and have never bothered them. My dill is basically feral, there is always some in different stages of growth around here and there, they don't seem to hurt it too much overall. Although every now and then I see a plant pretty much consumed.

I think they like fennel better though, we have one patch of fennel that volunteered and established in a corner of the garden, I'm totally amazed they haven't completely killed it, but it keeps coming back. I'd say, plant some fennel and move the worms to it, if they aren't all there already.

Thanks, everyone.  I like the idea of netting half of the dill and leaving the rest for the Blk. Swallowtails. I'm also going to spread the seeds throughout the garden since it's a perennial. And I'll plant other greens they like.  In my yard, they seemed to like the dill better than the fennel, but that's not really important.  Thanks again for your advice, and I'll try to do a better search on topics before I post.  Cheers!