Connecting with Nature: From Frangipani Caterpillar to Pseudosphinx Moth

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A month-long metamorphosis.

Last year I wrote about the lifecycle of St John’s monarchs – from caterpillars to chrysalises to marvelous butterflies. Though of course, I had read about this multi-phase transformation, somehow I had missed witnessing it before. I was amazed.

But somehow I was less excited when my husband suggested it would be fun for me to capture some frangipani caterpillars and see what they turn into.

Usually, the big striped caterpillars just seem to disappear once when they are done eating all the leaves off your frangipani tree. I knew that eventually the frangipani caterpillars turned into big gray furry moths. I had seen a couple. Not very attractive compared with the delicate fluttery monarchs.

No one I knew had actually seen their interim stage of development. Reportedly in their pupa stage they lie on the ground and look like dead leaves. No shiny green chrysalis hanging from a branch, decorated with shiny gold dots, like the monarchs.

Anyway, the deer and the storms had already destroyed our frangipani trees.

I didn’t think any more about caterpillars until after just Christmas when I was out walking along the Fish Bay road. I noticed a fairly large frangipani tree with only a few leaves left. It was crawling with caterpillars.

Hmm. Some of those caterpillars were not going to get enough to eat, as there were no other frangipani trees in sight. After only a moment’s hesitation, I pulled a plastic bag out of my backpack and grabbed a couple of the leaves along with a few of the larger caterpillars.

My younger son was visiting for the holidays and had been off at Reef Bay teaching his girlfriend how to surf. As it happened they pulled up in the old yellow Jeep just as I was turning onto our road.

“What’s in the bag, Mom?” he asked.

I held it open, “Oh, just some caterpillars”.

I got out a plastic crate and some mosquito netting and put the caterpillars inside. By morning the leaves were gone.

Now we needed fresh fodder. My husband and I set out early to discreetly search the neighborhood for frangipani foliage. We found some high up on a hillside and quickly made off with it. The milky sap was dripping from the stem but fortunately, I had another handy plastic bag in my backpack to wrap it in.

I thought the largest caterpillar was already fat enough to move on with its journey, but it kept eating constantly for about a week. We had to make a second fodder foray. Then on New Year’s Eve it stopped eating and started roaming around the crate at a fast pace.

I read that the caterpillar would ordinarily move away from the tree and look for a pile of leaves to hide in while it transformed into a pupa and then a moth. I thought about providing some cover but then I wouldn’t be able to see what happened.

By New Year’s morning, the big caterpillar had stopped roaming and looked dull and shrunken. I was afraid it was dying. I put it on the table to keep an eye on it. Then, it started having contractions that ran from one end to the other. It looked like it might bust open right then – a great way to start the new year!

All day my son and I watched over it, but not much happened. I poked it and it twitched, so I knew it wasn’t dead. By late afternoon I was still thinking it might transform so I took it to a neighbor’s party with me in a little box. No change.

In the morning I found a research paper that mentioned a ‘pre-pupa’ stage that could last several days, so I put it back in the crate and left it alone. I couldn’t watch it all the time.

One morning when I woke up and checked I saw that it just shed its skin and I was disappointed to have missed the transformation. I could tell it had happened recently because the pupa was still soft and yellowish. I saved the cast-off dried up skin.

Later it got harder and shell-like, and much darker. You could see where the wings would form.

During the pupa stage, the caterpillar body inside the shell is dissolved by enzymes that break down many of the tissues into component cells or clumps of cells that then gradually grow into new moth-body structures. Wow.

The research paper said it would be about 3 weeks before the moth formed and emerged from the pupa. I started checking on it around then but it was a couple of days late. And once again I missed the moment.

One morning I woke up and found the hard shell with just the end popped off and the moth beside it just lying there.

I brought it some bougainvillea flowers so it could eat some nectar and it moved a bit but never got very perky. (At first we went out looking for a frangipani flower but then I remembered that those don’t actually have any nectar. They smell good and fool the moths into poking around in the flower and pollinating it, but the moths have to find food elsewhere.)

At that point, I put them all outside. The moths only live about a week or so. After all their complicated and mysterious stages of development, the moths have that very brief time to find a mate, reproduce, get some eggs laid on a frangipani tree, and start the whole cycle all over again.

And we think life is short.

Photos by Gail Karlsson.


Gail is an environmental lawyer, and author of The Wild Life in an Island House, plus the guide book Learning About Trees and Plants – A Project of the Unitarian Universalist Fellowship of St. John. uufstjohn.com/treeproject.  For more articles and local information, go to gvkarlsson.blogspot.com or www.fishbaywetlands.com.  Contact: gkarlsson@att.net Instagram:@gailkarlsson