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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