Monarchs will wander off the milkweed when they need to shed their skin. Don't get too worried about it. Also, don't move the caterpillars because if they are preparing to shed, they are anchored to their spot and pulling them off can cause a problem.

Thank you for the info. I came down this morning and this is what I found. The other one Has already eaten through most of the old skin. I had no idea the process took so long. I imagine they will be hungry for my milkweed soon.

Sorry to be such worrywart. The first batch of any new species seems to make me into a very nervous mama. Also, I managed to kill the second batch of black swallowtails I tried to raise by attempting to move the early instars. Fortunately, I know better now and I did not touch these monarchs. Plus, of course, I am extra worried because they are monarchs, which are doing so poorly right now.

My third brood of black swallowtails seem to be doing fine. I am an old hand at that now!

Liz

I agree that it is a bummer when caterpillars sicken & die. It does happen, my understanding is that there are both viral and bacterial pathogens. Here in Madison, Ophyryocystis elektroscirrha is the main culprit. I have seen this one classified as a protozoan, and also as a water mold. My experience with raising monarch caterpillars is that about 80% of them make it to adulthood, when hand-reared. Out in the yard, maybe 1% or 2% survive and emerge as healthy adults. It helps to raise them in individual glass containers, and I also wash the milkweed leaves in running cold water, and dry them off, before they are fed to monarch caterpillars. There is a lot of hand washing and glassware washing involved, as you might imagine.