The carrot swallowtail had been in the "sling" position for almost 24 hours and I was starting to worry; I couldn't remember how long it normally took for them to pupate after them slung themselves up, but I don't remember it taking that long.
I was checking on her one more time tonight, and just happened to catch the very beginning of pupation--I've never actually been able to watch it happen before. At first her body was heaving, with each segment pulsing individually from the tail up. Here's a picture from early on; sorry for the low quality but I'm taking pictures in low light through wavy plastic here. But you can see here there are already some color changes.
Then suddenly it looks like the chrysalis just starts growing on the back of her head and starts spreading down her body, and it's not clear until halfway down that her old skin is being pushed off, just like when they molt between instars.
It took a huge about of thrashing and writhing to get the skin to detach from her tail, but the whole process of shedding her skin lasted maybe 60 to 120 seconds. After she was fully pupated she continued to writhe and pulse, and from the time I started watching until she stopped moving was about 20 minutes, and this happened, for the record, around 7 p.m. tonight.
The pupa continued to darken slightly after she finished moving, but last I checked was still green with yellow highlights, despite being on a brown twig with the container sitting on brown paper (the pupa can be either brown or green, depending on the environment).
Meanwhile, the little egg that I brought in a week ago has just molted to instar four already. They grow up so fast!