Monarch Butterflies in Winter

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By Bob Pish
All photos by the author.

Editor’s note: this post is taken from an email sent by the author to Forrest Mims. The author has graciously given us permission to publish his observations and photos on our blog.

A week or two ago when we had the cold snap a Butterfly Weed (milkweed) plant died back and its leaves turned black. When I went to cut it back I noticed a couple of caterpillars still on the plant. Assuming they would not make it through the cold and that the odds of them continuing their migration were thus slim, I decided to do a little experiment that might save them and show me some new things.

Knowing these Monarch caterpillars would not survive another cold snap, I made a makeshift Monarch House for them. It only had a dirt floor (since they are prodigious eaters--and poopers) but it contained three fresh Butterfly Weed plants for the new residents and vents for airflow as well as a large bay window for my viewing pleasure and a warm light overhead.

As I started collecting caterpillars, I wound up with a dozen–at least I think it was a dozen. They get hard to count. I placed them in the enclosure and proceeded to watch them really munch away. They can really strip the plants.

Click images to enlarge.

Then after a couple of days a bunch starting climbing up the dried blackberry sticks I placed in the enclosure just in case they wanted to form a cocoon on something solid.

They did use the sticks but climbed up to the plastic roof, formed a button of silk and hung from it in a “J” shape. You can see that they also laid some of the silk over a rather large area and that is the white streaks in the photo below.

I was all set to watch them use the silk making mechanism and weave a cocoon. But the next morning three had already formed chrysalises instead. What was interesting was that the chrysalis was only about 70% as long as the length of the caterpillar. So I was bound and determined to watch more frequently and during the day, I stepped out for ten minutes to pick some lettuce from the garden and by the time I got back another one had pupated. No weaving, no prep, just pop and they are formed. That amazed me. Maybe they do not being watched. So about this time eight caterpillars were either hanging or inside their chrysalises.

It would be interesting to know the purpose of the little reflective spots that run half way around the perimeter.

But there were still some caterpillars in the “brush.” Included in the four that were not yet ascended was one who went out of the pot and was sitting on a clump of the potting soil at the bottom. I picked him up assuming he had fallen out and put him back in a pot. The next morning he was again on the exact same spot. I put him in a different pot and the next morning he was again back on his favorite spot. I did this four times before deciding to quit. I have named him “Wrong-way Corrigan.” This morning I decided I would take a photo of him on his patch of dirt. But he had moved and was sitting on the side of the box about two inches above the dirt and had not moved all day.

In the meantime two of the other three caterpillars have moved up to the chrysalis level. I have theorized that this difference between the two groups arriving at the chrysalis stage represents two separate batches of eggs.

Now I am just hoping that the butterflies will not emerge until the grandkids get here for Christmas.

Once the butterflies emerge I have no easy way to care for them and was considering taking the Monarch apartment to a local nursery that has a green house.

Update (20 December):
Well on checking the Monarch House today I saw that Wrong-Way Corrigan had turned around and was pointed down and although he had not moved far, appeared to be ready to go back to his “comfort clog” of dirt. I could see the longing on his face. At least I think it was his face. Those caterpillars have similar front and back ends.

Notice the horns on both ends.

Of the two caterpillars that had climbed up to the cocooning area near the others, one had formed a cocoon and one had vanished. I ruled out being eaten by a bird as there are not that many in the Monarch House. Perhaps facing such a cataclysmic change he/she/it decided to go back down into the bush were he/she/it was safe and there was plenty of food. Not unlike many humans. And I did see one caterpillar continuing the deforestation of the plants below.

Interestingly enough, the two “second hatch” caterpillars that had just crawled up to the cocooning area never crawled up the blackberry sticks provided but went up the cardboard. All the “first hatch” had used the sticks. Also interesting, rather than form a cocoon on the plastic, the one that stayed in Up-Land had attached itself to the vertical cardboard wall.

I just went back to check on Wrong Way and saw that there were two caterpillars down in the bush. The one I had seen earlier eating away and one that is suspended beneath a leaf in the stage right before the chrysalis forms.

So indeed the second batch are different in many ways.

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4 Responses to Monarch Butterflies in Winter

  1. This is a fascinating report. Monarchs that migrate through Texas during October-November on their way to Mexico are fourth generation from those that left Mexico the previous spring. Those going to Mexico are not returning there, since they’ve never been there. I’ve never heard about any flying to Mexico stopping to lay eggs along the way. That’s what happens when they leave Mexico and fly through Texas during spring.

  2. Susan Smith says:

    Wonderful story and photos. What part of the country are you in? I’ll be interested to hear if & when these caterpillars emerge. Do you know if your butterfly weed is Asclepias tuberosa? I was told be a local entomologist (& heard it from a couple gardeners) that monarch caterpillars did not eat this plant even though it is a milkweed. However, from what I can see in your photos, it appears to be A. tuberosa and they certainly are devouring it!

    • Bob Pish says:

      The tag on the plant is Red Butterfly Weed, “Asclepias curassavica”. The caterpillars did indeed appear to enjoy this plant to the point that there is but one small bloom left for Butterfly food.

  3. Pingback: Winter Monarchs: Update and a Backgrounder | Citizen Scientists League

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