Pat’s Wildways: Monarchs and Milkweed

By Pat Foster-Turley
December 23, 2022

I thought I knew all about monarch caterpillars turning into chrysalises and then into butterflies. We all do, right? From the start of books read to us as children like “The Very Hungry Caterpillar,” we all know that caterpillars turn into butterflies. Many of us, myself included, have collected monarch caterpillars from our yard, put them into “butterfly habitats” and fed them milkweed (their host plant) until they make a hard green chrysalis, and then in a couple of weeks, come out of this shell as an adult butterfly.

This year I was disturbed that I saw few butterflies of any species in my yard despite the many milkweed plants I was proud of that reseeded and spread throughout my yard, and the various other flowering plants that attract the adult butterflies. Usually by the fall I have recorded a handful or more caterpillars and found a few chrysalises scattered around. But this year was different. I asked around and yes, other people did see the usual amount of butterflies. It must have been something about the location of my yard or who knows what.

But a couple of weeks ago, well past the usual monarch migration season, Susan Gallion and I spotted an adult monarch butterfly resting on a bush and we went outside to further inspect it. And then we spotted a monarch caterpillar, and another and another. There were maybe 10 caterpillars scattered around my butterfly garden. Some were munching on the last leaves of my milkweeds and others were on the garden floor heading somewhere.

Susan was the first to notice one caterpillar in an unusual hanging position and we both started watching it. And, right in front of us, it turned into a chrysalis! It was a most amazing natural phenomena to watch in person. The caterpillar started turning black, then a bright green part started forming and spreading from the bottom until it covered the caterpillar. This critter vibrated rapidly, making it difficult to focus on, then it squeezed out the remaining black parts of the original skin and all that remained affixed to the branch was a solid green chrysalis. It only took maybe 15 minutes for this creature to totally change its shape and coloration, from a black and yellow striped worm-like organism to a vivid green enclosed sac! We were very lucky to see it just at the right time. Susan and I had never actually seen this happen, although we were both familiar with caterpillars and chrysalises. We both thought it took hours for this to happen in some mysterious process that happened overnight. But no, it happens in mere minutes! If you want to watch this yourself, check out this real-time video of the process and more details here.

I was transfixed at how well the chrysalis blended in to the bush it had decided to metamorphose on and, as a joke, sent a Facebook photo asking people if they could find the chrysalis on the bush, and only a few could. For a while I pondered the thought that maybe the caterpillar could somehow see the color in various plants and picked one with good camouflaging potential to settle on. When I found a couple of other caterpillars crawling around on the ground I carefully lifted them on a stick and moved them to this “perfect bush” hoping to give them some help.

But that was proven wrong. Although I searched the bush carefully for more chrysalises I never found another. But I did find one quite a distance from the milkweed plants hanging totally exposed on the gray metal of a lawn chair. So much for the color recognition hypothesis.

So now I am watching two chrysalises in my backyard, one in the bush and one on the lawn chair. They are due to become butterflies any day now. But it is also a very cold time outside now, maybe too cold for them to survive. We will see.

There is an ongoing controversy about the possible harm of planting tropical, non-native milkweeds (like mine are) here in Florida since it may be that the presence of milkweed here at the wrong season could confuse the monarchs and impede their migration south. I’ve also recently learned that allowing milkweed to continue growing year round magnifies the load of a parasitic disease that harms butterflies from year to year, thus weakening, or ultimately killing the monarchs that feed on these plants. You can find out more at this link.

I now am worried about all my reseeded tropical milkweed plants that I was so proud of just weeks ago. Live and learn is my motto. I always seem to learn something new, even about caterpillars, chrysalises, and now, milkweed. Who would have thought?

Pat Foster-Turley, Ph.D., is a zoologist on Amelia Island. She welcomes your nature questions and observations. [email protected]