Do caterpillars succumb to heat stroke?

[Victoria]

This is my third year of raising caterpillars on my screened-in porch, and over the past two days I've witnessed a significant die-off among different instars. I've never had this problem before, so I don't think it's my methodology.

Up here in northeastern Illinois we've experienced a heat wave with the heat index repeatedly reported about 100 degrees. I was wondering if caterpillars have difficulty coping with extreme heat/humidity?

I'm sorry I don't have any pictures -- mine do not look like the one in Dave's post (where it looks "burnt"). Instead, I just find them lying at the bottom of the jar as if they've just keeled over.

Not all of them have died, but I hate to keep finding bodies. I have stopped looking for caterpillars "in the wild" in case they have a better coping mechanism.

[John Beaulieu]

This is our first year of organized monarch raising and we are doing it in a glass enclosed porch which gets late afternoon sun. We too, here in central Ontario, have the heat wave and the porch can get unbearably warm some days. It has not seemed to affect the caterpillars and we have lost none (so far). We have six in chrysalis at this time with more getting to that point. One butterfly was released a week ago. These are from eggs found around the area and on my own milkweed (tropical and swamp) in my garden. I caught a tattered female monarch last week and kept her overnight in a pen with a potted common milkweed. I was hoping that she would lay eggs on the plant. After releasing her, we checked the plant and figured that there may have been around 10 eggs. Today we counted over 30 little caterpillars which are quickly consuming the plant. This should be fun releasing that many butterflies!

[Keith Petrosky]

I guess if it's too hot and they cant get out of the sun they would die.

[MILW]

I would try to keep them shaded at least... I had one container get direct sun and all the cats in it died