It’s Cold. Can Monarch’s Survive?

It’s getting cold here in Houston.  According to the latest weather reports I’ve seen, the temperature might get down to 22 degrees tonight.

Although we’ve been keeping a few Monarch Caterpillars indoors, we’ve kept several outside, we just covered them up to provide some insulation.

As we were covering our plants and pipes tonight, Leecy and I also decided it might be a little chilly for the Monarch Caterpillars that have been in our outdoor enclosure.

Little did we know we had 15 Caterpillars!  Fortunately, we’ve been protecting much of our Milkweed so we should have plenty enough for them to eat.

Monarch Caterpillars Brought Indoors Before 20 Degree Freeze

Monarch Caterpillars Brought Indoors Before 20 Degree Freeze

That got me to thinking.  How cold can it be for Monarch Caterpillars to survive?  I was able to find out that Monarch Butterflies can crawl at temperatures of 41 degrees, and need a temperature of 55 degrees to be able to fly (see here for reference).  In terms of mortality, Monarch Butterflies can survive temperatures of around 17 degrees, but not for very long, and around 50% of Monarch Butterflies will die at this temperature.

But what about Monarch Caterpillars (not Butterflies), how low can the temperature be before they begin to die?  Unfortunately, I couldn’t find the answer to this question.

Can anyone help answer the question above?  I’m really curious.

Valerie Evanson - I’ve been wondering that myself, but haven’t come across anything on it. Since they overwinter as adults, I’m guessing they aren’t as hardy as swallowtails. Looking at my pupas that are overwintering, the swallowtail and moth shells are very tough in comparison to the monarchs. In respect to species that overwinter as pupas, my one insect book quotes Dale Schweitzer, “A good general rule is that underground pupae should not be exposed to temperatures below 20-25 degrees F. Unless your climate frequently has nights below about 10 degrees F the easiest approach might be keeping above-ground pupae outside in a shaded sheltered place.” So . . . a monarch would need it to be warmer than that. I’ll see if I can find a more definitive answer, but first I need to get out the snow blower and clear the driveway. :) January 12, 2011 – 10:14 am

Valerie Evanson - I contacted Karen Oberhauser at MLMP (U of Minn) and she said there is no good data on the subject and that one of her students is starting a study on it.January 13, 2011 – 10:30 am

Tonya - Do you know where i could get butterflies to release on feb 6 for a meorial ceremony ?January 13, 2011 – 7:42 pm

texdr - Yea that’s what I found out as well. I emailed Dr. Bill Calvert and he essentially said the same thing. They really don’t know.January 13, 2011 – 8:24 pm

texdr - No I’m sorry I don’t. Are you located in Texas? It might be tough to get Butterflies right now (I’m guessing) because they need pretty warm temperatures to be able to fly.January 13, 2011 – 8:27 pm

leecytx - Well we kinda found out a little on this post. Today the temperature was 60F so we were looking at the milkweed we had outside and sure enough, we found 3 little cats. They were 1st instar stage. We did not see them on the day we brought all the others inside & the temps outside got down to 22F (we know that because our pool automatically comes on 27F that temp to keep the pipes from freezing). We have left them outside for now and maybe we can test this whole question on these guys -especially since we are almost out of milkweed! Stay tuned …January 15, 2011 – 7:32 pm

Sandi Barr - Hi, I live in So.Cal (North Tustin). It was 41 deg. last night and the grass has frost. I know that isn’t cold for some of you BUT I must have at least 50+ Monarch cats munching in my yard. The weather has been so unpredictable. It will get in the 60′s today with lots of sun BUT it is supposed to rain by Sun. Should I just bring inside as many of the cats that I can? I have 2 big cages. I will do anything to rescue them. Directions please :) SandiDecember 20, 2012 – 12:27 pm

E - hi i live in canada. my mom and i found a monarch butterfly on our front step. we thought he was dead. when we took him inside and warmed him up he started to fly around. we put him under a big strainer with banana and apple slices. there is still snow on the ground here and it is cold. we don’t want him to die. should we keep him with us or should we let him go? is it ok to let him go when there is snow on the ground? how warm does it need to be outside for him to live>April 24, 2013 – 9:30 pm

texdr - That’s amazing that you already have a Monarch in Canada! I would really recommend you report your sighting to Journey North ( I’ve never heard of a Monarch making it that for North this early in the year.

To fly, Monarch’s need the temperature to be at least 50 degrees Fahrenheit. They can survive temperatures below freezing for short periods of time, but the bigger issue is it will need a source of food and if there is snow on the ground, you probably don’t have any nectar plants for it to feed. I don’t think they will use Apples or bananas. However, I do have a solution, and if you do a search on my blog, I’m pretty sure I have some posts and a video or two about how to do what I’m going to suggest.

You can feed it gatorade, or this juice product we have in the States (not sure if it’s in Canada) called Juicy-Juice. Soak a cotton ball in the juice. You can then try placing the monarch on the cotton ball. If it’s really hungry (and/or smart) it will start feeding. Sometimes they need a little encouragement, so you can hold it by the top of it’s wings, and have someone every so lightly unfurl it’s proboscis into the cotton ball with juice. After a couple of attempts, it should start drinking.

As far as letting it go, if there are any flowering plants, and if the temps are above 50, you can probably let it go, although it may really have to hunt for food. Depending on if it’s male or female, if it’s the latter, she’s probably going to be hunting for milkweed to lay her eggs on.

Hope that helps somewhat. Let me know how it turns outApril 24, 2013 – 9:55 pm

Elizabeth - I found this on a website about temps and monarch’s cat

cold weather (below about -5F) does kill monarchs, at any stage, and definitely slows down their development.December 20, 2013 – 10:21 am

texdr - Thank you Elizabeth, that’s good information!December 20, 2013 – 8:45 pm

Tess - I have been bringing my Monarch caterpillers in when the temp fall below 40°. I phoned the Butterfly Encounter Group and they said the caterpillers will die at 32°. They are the only ones I’ve found that knew the answer.January 17, 2014 – 12:45 pm

texdr - That’s good information! Thank you for sharingJanuary 18, 2014 – 10:29 pm

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