Monarch chrysalis

Empty Monarch chrysalis

November seems to be the time of leftovers and left-behinds, as animals head south, or into hibernation, or otherwise start preparing for winter. November is when I start seeing the summer’s empty birds’ nests, old cocoons, empty shells of things. It’s probably in part because with the animal and plant life disappearing, the eye is drawn more to the inanimate.

I spend a lot of time staring at the ground in November, and so I was doing when I came across this. It was just a bit of curled up paper hidden in the grass, and I nearly dismissed it as a bit of birch bark before pausing for a better look. Stooping down, the bit of paper revealed itself to be an old, long-since-vacated chrysalis. Naturally, I’d left my camera back at the house on this particular outing, so I decided to break off the grass stems and bring it back.

Caterpillar silk is surprisingly strong. I broke off the two grass stems that the chrysalis was obviously attached to, and lifted gently, but there was still another. So I snipped that dead leaf and tugged again, and it was still affixed to something. I broke five bits of grass to finally be able to get it out, and a sixth was hanging by a thread of silk, which I sawed through with a fingernail. No surprise this stuff makes good clothing.

The light was waning when I got back to the house, but I ran off a series of shots. Even though the sides of the chrysalis are in tatters, enough of it remains intact that it’s easy to see the identity of its former occupant: The roundish top, the beaded ring a third of the way down (now lined with black), and the general size all clearly mark this as a Monarch chrysalis. While it housed a metamorphosing caterpillar, it would have been minty green, and that ring of beads was gold.

Empty Monarch chrysalis

When I started taking photos, I was surprised by the pattern of black on the top, where it attached to the grass. The stem itself is called a cremaster, and is formed from the tail-end of the caterpillar just before it sheds its skin for the last time. The caterpillar makes a silk “button” then shoves this black rod into it in order to affix itself; once done, it hangs from its tail, curls into a J, and splits its skin along its back. For an amazing sequence of photos, strung into a video, of a Monarch caterpillar changing from caterpillar to chrysalis, you should check out this NPR page, a commentary by Julie Zickefoose. Julie’s also got some amazing transformation photographs at her own blog – here, here and here, for instance. Every year she brings in a couple of fifth-instar caterpillars so her family can watch them metamorphose from larvae to butterflies.

Empty Monarch chrysalis

The outside of a chrysalis or pupa is effectively the sixth skin of the caterpillar (it’s already shed five, to get here), rather than an external structure such as the hairy cocoons moth caterpillars make. Because of this, many of the structures of the winged-adult-to-be are defined in its hard shell. With moth pupae, especially, it’s possible to see the shape of the wings and antennae of the adult moth. Butterfly chrysalids need to be more camouflaged and tend to show other shapes (or at least, I presume that’s the reason they show other shapes; they don’t have the same hairy cover that above-ground-pupating moths make).

But I did notice something else on this one: the spiracles that line the abdomen of the insect. Spiracles are the insect’s “nostrils”, the holes through which it breathes. All insects have them, but on many (most?) they’re well-hidden. I thought it was interesting that they were so prominently visible on this old shell; you can see them on the green chrysalis, too, but not as clearly.

And then the other interesting thing I discovered, while poking about BugGuide.net, was mentioned on this photo and this photo… Apparently you can sex the insect inside the chrysalis based on the presence or absence of a small line at the base of the string of black dots. I’ve indicated it in this photo using a yellow arrow. If the line is present, the insect is a female; if it’s absent, the butterfly is male.

This is the first Monarch chrysalis I’ve ever seen in the wild. It would have been more exciting if it had actually contained a Monarch at the time that I found it, but I still think it’s pretty cool!

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9 responses to “Monarch chrysalis

  1. Noooo! You can sex a chrysalis!! Seabrooke! Whaa??
    The marvelous in nature, indeed. Thank you, thank you, thank you.

  2. Glad you enjoyed it, KaHolly!

    And I thought that might be of interest to you, Julie! Wasn’t sure if you already knew of it. You take so many in, and even though you’ll get to see the adult when it ecloses to learn its sex, it’s kind of fun to know these things in advance. Presumably the lower slit on the chrysalis is the female’s reproductive tract opening.

  3. Terrific info on sexing the chrysalis. Ain’t Bug Guide grand? Hope your Moth Guide is coming along. Told my wife I wanted it for Christmas–some Christmas, not necessarily this one.

  4. Spiracles! So that’s what they are. A Monarch chrysalis has got to be one of the most beautiful things on the planet; maybe people who wear nose piercings are only imitating Nature, after all. :)

  5. Awesomeness! Thanks so much–got to get that hand lens out now to sex the chrysalis — I love that the learning will never end!

  6. Seabrooke,
    Reading your post, I wasn’t clear on one of the details of the transformation from the caterpillar to the chrysalis. The caterpillar actually hangs itself on the silk button from its last pair of prolegs, but the cremaster is a part of the chrysalis. As the last caterpillar skin slides off, the chrysalis actually reaches out of the skin (close to the end of its shedding) and attaches the cremaster to the silk pad. It’s described pretty well here (http://www.learner.org/jnorth/tm/monarch/ChrysalisFormationLPB.html). It’s pretty amazing that they nearly never miss in the transition from hanging bycaterpillar skin to hanging from cremaster! I’ve watched them do this, but it’s not something you can really see well as it happens so fast. It’s an absolutely incredible phenomenon, this process of metamorphosis! And a great teaching tool!
    Melissa

  7. BugGuide’s one of my most-frequented sites, JB! And I’m pleased to hear you’re looking forward to the moth guide! You’ll have a bit of a wait, though, if you’re asking for it for Christmas. It should be out for spring 2012, so depending on when your birthday is, that might be a possibility…

    I agree, Lavenderbay – wish I’d seen this one in its summer colours!

    Me, too, Amy! There are so many fascinating things to discover out there.

    Thanks for the clarification, Melissa! I was a bit confused about the exact process, too, not having watched the process myself. And you’re right – it’s like caterpillars were made for sharing with kids. :)

  8. Pingback: » Butterfly Drawings Butterfly Facts

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