on becoming green

For the past few weeks, I’ve been saying that I’d try to photograph the transformation of a Monarch from caterpillar to chrysalis (pupation). Unfortunately, until this week, I struck out repeatedly as each caterpillar seemed to choose a time when I wasn’t available to watch. This week, I finally managed to catch most of the action one afternoon. I say “most” because I stopped watching for awhile to make a stirfry for our dinner, and a few minutes after beginning, I stepped out of the kitchen to check on the caterpillar and….arghhhhh…it had shed its skin (exoskeleton) and was already becoming a chrysalis. So, I’m missing a small part of the sequence of events. However, there are enough photos to give you some idea of what transpires when it’s time for a Monarch caterpillar to go green.

Above is a thumbnail verision of a much larger (235kb) “panorama” that I made out of photos taken on August 17th. I’ll just give a brief explanation of what you see taking place in the sequence.

When it’s time to begin to pupate, the caterpillar makes a small patch of silk to attach its hind end to some object — in this case, to a square of window screen. At first, the caterpillar may remain curled up, but soon, it will relax and hang so that it looks like the letter “J”. That can go on for about a day. After a few hours, the front end of the caterpillar begins to look somewhat tinged with green. Shortly before it’s about to begin to transform, I’ve found that the caterpillar often begins to make repetitive movements with the head and front pairs of legs — clasping motions that seems somewhat similar to when it’s working on eating a leaf. Then, after awhile, these motions cease and the caterpillar droops with head downwards. The front antennae seem to deflate and hang very limply, and then flatten and become twisted. The legs also seem to shrink during this time. At this point, pupation will occur quite soon. What is not shown in this photo sequence, is the skin splitting, and the pupa wriggling free while it hooks the cremaster (the black stem that it hangs by) to the silk as the old set of legs fall away with the skin. After the skin has fallen away, the pupa moves around a bit, seeming to flex and stretch, then finally assumes the general shape of the chrysalis. As you can see from the photos, the abdominal bands and wings are quite visible even at this stage. Soon after, the surface of the pupa begins to change as it forms the outer membrane that will protect the pupa for the next ten or so days as it transforms into a butterfly. The chrysalis does change in appearance even after this — becoming harder, a little darker, and with more defined shape and markings, but the above photo is how it looks within hours after pupation.

Monarch update:
I’ll use this post as an update to the Monarch situation as of this morning. There are 12 “good” chrysalises now. However, there are an additional three that look to be duds (apparently, this is a common thing due to parasitism, etc…). Of the duds, one turned an odd shade of brown right after pupating. I’m keeping it around, but it looks weird and I have my doubts that anything will emerge. Another fell from the cremaster before hardening and it is very misshapen now. And a third is misshapen as the caterpillar just pupated while lying on its side on a leaf. I held a piece of folded facial tissue up to the cremaster and managed to get it to hook onto it, but the shape of the pupa is still rather odd. I guess we’ll just have to see what, if anything, emerges from those chrysalises. All of the caterpillars seem to be doing very well — and many are reaching final instar stage at about the same time, so it’s been a little hectic getting everyone into separate jars with screens over the tops. Until close to pupation, I find that the caterpillars will stay in their trays if well supplied with fresh leaves, but they become very restless and prone to wander far once they begin looking for a place to pupate. Last week, one of them struck out in search of a good site and I found it about an hour later, right across the room, sticking to one of Don’s hats that had been left on the hall bench about 15 feet from the caterpillar trays.

In other news, the second of the Monarch butterflies eclosed on Thursday. I shot the photo below (click on it for larger view) yesterday morning before it was released. This is the first female to emerge. Unfortunately, the migration tags haven’t arrived yet, so it wasn’t tagged before release. I hope they arrive early next week as I have a chrysalis that is getting ready to eclose, and there will definitely be quite a few more eclosing this coming week. I also shot this little mp4 movie of the Monarch on my hand while I was out in the sun porch. The porch is an ideal place for the butterflies to eclose as they are safe and can’t get lost while they’re drying out and building up strength before taking flight. The Monarch that eclosed this week, emerged in the kitchen on Thursday evening. I left it for awhile and when I went back to check later, it had disappeared. I wasn’t too concerned as I figured it would come out of hiding the next morning. The biggest fear was that one of us might accidentally step on it. Friday morning, I looked around and couldn’t find it, but then at around 8 a.m., it came wandering out onto the kitchen floor from beneath the Hoosier cabinet where it must have spent the night. It wandered around, flexing its wings as though it was doing morning stretches. Sabrina watched and sniffed at it until it climbed up onto her nose with its little hooked feet. She definitely didn’t care too much for having it walking around on her head while it flexed its wings, so I removed the butterfly and placed it out in the sun porch for a few hours before sending it on its way.

The Black Swallowtail (Papilio polyxenes) caterpillar also pupated this week. The chrysalis looks like a piece of beige treebark or a bit of wood. I’ll post a photo sometime soon.

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6 Responses to “on becoming green”

  1. robin andrea Says:

    Excellent photo sequence. I can really see how the caterpillar relaxes and the antennae hang limply as it prepares itself to transform. What an amazing process. The movie is so lovely. Watching those monarch wings open and close, while she is perched on your hand is really lovely. Wow, Bev.

  2. burning silo Says:

    Thanks, Robin. I’m probably as much fascinated by the behaviour as the outward appearance. I still find it amazing that insects undergo such remarkable transformations in short periods of time, and become something quite other…. becoming a pupa or a flying insect.

  3. Peter Says:

    Looking good Bev. They must be waiting for you to leave the room! If you noticed on NatureNS, Larry & Alison Bogan seems to have quite the chrysalis population in the back yard too, 48 by her count.

    I hope those tags come soon, and with some luck they will be found again.

    I’ve noticed on my walks that I am seeing less and less tattered monarchs and more fresh winged.

  4. burning silo Says:

    Peter – I think you’re right about them waiting until I’m not around! I did see the post about the chrysalises at the Bogans. Sounds like they had a good crop of Monarchs there. I’ve been seeing quite a few fresh winged Monarchs around here too. Yesterday, while walking around here at the farm, I saw 6, so it looks like the “outdoor” gang are doing quite well.

  5. Ruth Says:

    Your photos are stunning. I am happy that someone is finding a larger number of monarchs. I looked for 2 hours to find one…and we used to have plenty.I am trying to nurture one lonely caterpillar and hope to see it emerge as well.

  6. Bjørn Weis Says:

    I have had exactly the same frustrating experiences with the metamorphosis from larva to pupa. The last couple of days I have watched several larvae ready to pupate, then diverted my attention for what seems like just a few seconds, and then: -hey presto! The pupae hang there, you can almost hear them laughing!
    We have quite a few Monarchs here, north of Auckland, New Zealand, and it is fascinating for the kids to watch the almost unbelievable transformation from an earthly crawling grub to a heavenly angelic creature.
    Your photos are admirable. Thank you for sharing them.
    Cheers