However, I noticed that the individual in these photos was not looking especially lively. Even though the caterpillar looked pretty good - slightly faded, perhaps - something was amiss. So in we go for a closer inspection.
Tachinid flies, which rather resemble house flies, are major caterpillar predators and attack the cats by sticking an egg to the the larva's exterior. In short order, the fly grub hatches from the egg and bores directly through the caterpillar's skin and into its interior.
In this photo, we can clearly see what must be the grub's exit hole. What a show that must have been, and I'm sure you wish I had caught the grub bursting from the caterpillar's husk on video so you could enjoy that bit of cinematic loveliness as you ate your breakfast. But such a video was not to be - I suspect that these tachinid fly grubs tend to emerge under cover of darkness.
As I was making these photos, this tiny chalcid wasp alit on the caterpillar husk and began looking around. This little wasp is looking to parasitize the fly by laying eggs on either the fly grub or its puparium. The world of parasites and parasitoids (the latter generally kill their hosts) is truly strange and multidimensional.