I've seen that too. I know that butterflies often use the sun to regulate their temperature, and caterpillars probably do that somewhat also. And some species must be more cold-hardy than others. I know the Monarch caterpillars and some others can tolerate mild freezes. I've seen Gulf Fritillary caterpillars survive freezes and the butterflies sometimes stay well into the winter here. But there must be minimum temps for caterpillars, otherwise reproduction would just continue during the winter. I've got a little Monarch caterpillar I'm raising. Didn't see the mother and there were Queen butterflies around the day I found it, so I thought all the eggs were Queen eggs. I've since seen Monarchs butterflies, two were flying around elsewhere when I was away from home and one also came into my yard for a brief time to nectar. It's sad that there are so few of them. In the past, there were sometimes a lot of them this time of year (it's peak migration time here).
But
angele said:hi everybody. I've got a question for you. Is there a point at which the night time low temperatures become too low for caterpillars? I have a pretty good size black swallowtail cat on the fennel & would prefer to just let it be but our nights are getting pretty cold; low 40s and upper 30s. Then, there are some real small ones on the parsley too. The caterpillars are definitely in torpor first thing in the morning but as soon as the sun hits them they start getting active.
