In Early December I attempted to raise all 31 monarch caterpillars which hatched on my two milkweed plants. I knew from the start that I wouldn't have enough milkweed, but went ahead anyway, hoping I could get them to their 5th instar on Milkweed and then finish them on squash.
I was barely able to do this. I switched most of the cats to squash between their 4th and 5th molt. The squash I used was calabaza, which not only turns their frass orange, but makes it very wet and difficult to clean up. Milkweed frass rolls around very easily and is a breeze to clean up, but the Calabaza frass was wet and stuck to everything, including the pieces they were eating from. It was a nightmare to keep them clean. I changed their bedding every 4 hours and it was still a mess.
After some trial and error, I was able to devise a semi-clean way to feed the squash: I skewered a square chunk of squash, leaving the ends of the wood skewer long enough to prop the squash up off the bottom of the container. This gave the cats a clean surface to stand on, and their frass, for the most part, fell to the bottom of the container.
Nevertheless, it was impossible to keep the inside of the containers dry enough, and I lost about 1/2 of the caterpillars to infection. Those that did pupate made strange-looking, wrinkled pupae, some with black spots.
About half the chrysalises pooped out before eclosing, and the other ones produced butterflies that were too wet to fully eclose (they stuck to the chrysalis) or they emerged with deformed wings. Out of 31 caterpillars, not one made it to a healthy adult.
If I find myself in a similar situation in the future, I'll choose from the biggest, healthiest cats to raise, and euthanize the rest (I hate doing that, but I'd rather have a few healthy butterflies than none.) Also, I will use a drier squash like pumpkin. Calabaza is too wet, and all the problems I had were related to moisture.