Most of the caterpillars are now in their 3rd instar, but I keep finding a few that are still in their first or second instar.
I’m not sure if they hatched later, or if they got delayed – maybe by running low on fresh food. When we go to the farm I leave lots of leaves for them, but since it’s been so hot, sometimes the leaves are dried out by the time we get back. It doesn’t seem to bother most of the caterpillars – they hang out on the freshest leaves, and move quickly onto the new ones when I clean the cages.

I’ve figured out a good way of making sure I don’t lose caterpillars. Last year I lost a few when I cleaned out the old lilac leaves – I missed seeing them and they got thrown away. Now I put all the old leaves in a bucket with a small jar of fresh leaves, covered with a piece of screening to keep out predators. Over the following day all the remaining caterpillars migrate to the fresh leaves, and then I can move them back to the cages.

Here is a second instar caterpillar shedding its skin – it just walked out of it.

And here are two third instar caterpillars.