Silkmoth cocoons

Promethea Moth cocoon

First, apologies to all you folks who subscribe to the blog who may have been pinged with two nonsense posts over the weekend. I was doing some work with the site, having finally decided to bite the bullet and roll my personal website into the account I already had set up for my blog here at Since the top banner now reads my name, rather than The Marvelous in Nature, I had to insert a static header for The MiN on the blog page. As reader Dave smartly deduced and commented, I did this by using a sticky post – not realizing it would go out on the RSS feed! Fortunately, I think I’m done fiddling (for now). Swing by the website to see the new look, if you haven’t already.

On to other things… I thought I should post about these before they get to be really old news. A few weeks ago, on a relatively mild day for mid-February, I’d taken Raven down the road for her walk. I don’t normally go out along the road, since we’ve got plenty of acreage to wander which has the benefit of being somewhere that Raven can be off-lead. But the temperature that day was above freezing, which made the snow wet and heavy such that it would clump in my snowshoes if I tried to use them. And yet, it was still too deep to be able to hike without the snowshoes. So I went down the road.

As I was walking back, my eyes scanning the bare tree branches along the edge of the wood, I saw something attached to one of the tree’s branches. It looked like a dried leaf. Which isn’t actually all that unusual, because trees do sometimes retain a leaf here or there, or one of them gets caught on a twig in the fall. But something about this particular one looked different, almost out of place. So I braved the roadside snowdrifts to go investigate.

Promethea Moth cocoon

Which turned out to be completely worthwhile. The dead leaf resolved itself, as I got closer, to be a cocoon. It was about two inches long, thick and heavy. On a whim I decided I’d bring it home, and hopefully when the moth inside emerged I’d be able to see who its maker was. I had a pretty good idea that it would be a silkmoth of some sort, just by the size of it. Not many other moths would make a cocoon that large.

I pulled out my copy of Tracks & Sign of Insects after I got back to the house. There’s a pretty good section on cocoons, and given the size and visibility of silkmoth cocoons, they are reasonably well-covered in the book. I expected I’d probably find my cocoon in there, and sure enough, there it was: on page 224, a photo of a cocoon that was almost an exact match. I read through the text to be sure, but it seems that there’s only one moth that makes a cocoon like this.

Which is the Promethea Moth, Callosamia promethea. The caterpillars of this species roll themselves in a leaf to pupate, but before they do they secure the petiole (stem) of the leaf to the branch it’s growing from with a copious amount of silk thread. This binding prevents the leaf from dropping from the branch in the fall. The only other species that make narrow, tapered cocoons out of leaves like this either don’t occur in my area, or don’t bind the leaf to the branch so that it drops in the autumn and spends the winter among the leaf litter.

Promethea Moth cocoon

I spent the rest of the walk back scanning the trees, but didn’t spot anything else until I’d nearly reached our driveway. By that point I’d stopped looking closely at the branches, and it was almost by chance that I happened to spot a second cocoon hanging from a branch about 18 feet high, just to one side of our driveway. It was the same type, and I returned to the house to get a long-handled hook with which to pull down the branch. Both cocoons are now on our screen porch, waiting for warm weather. Promethea Moths generally emerge in late spring, so it may not be till June that they come out. I’ll definitely be posting a follow-up once they do, though! Surprisingly, I’ve never seen this species before, so it’ll be a new observation for me.


Author: Seabrooke

Author of Peterson Field Guide to Moths. #WriteOnCon Mastermind. Writer of action/thriller SF/F YA. Story junkie. Nature nut. Tea addict. Mother. Finding happiness in the little things. Twitter: @SeabrookeN / @SeabrookeLeckie

6 thoughts on “Silkmoth cocoons”

  1. I live at the Queen’s University Biological Station which I think is not far from you. We had a great June for Promethea moths in 2010. I would say they were the second most common of the large slikmoths at our mercury vapour and blacklights. It was a fantastic spring/summer for silkmoths in general. Lunas were most abundant, then Prometheas, with Io, Polyphemus and Imperials being a little less common but still numerous. Cecropias were fairly scarce. We also had a fair number of the smaller rosy maple moths.

    I’ve certainly been learning rather a lot of new information and identification tips for the smaller and less familiar species from your blog. I can’t wait for the moth book next year.

    1. Not too far, Mark – perhaps 30 km, as the crow flies. That’s pretty cool that the silkmoths were so abundant last summer! Up here I recall being somewhat underwhelmed, wondering where they all were; we’d seemed to have more the summer before. Apparently you had them! ;)

      I do really miss the lake house we had, set in the Arch as it was. This place is nice, and I love having all the land available to roam, but there’s just something special about that Arch habitat.

    2. Mark,
      I am desperately seeking wild silkmoth cocoons to enliven the gene pools of inbred populations that I rear in my backyard; if you can mail me a dozen promethea or cecropia I shall be indebted.

  2. I was searching the internet about the Polythemus moth and found your blog! Thanks for the fun information on their cocoons, I don’t think I’ve ever seen one. I have, however, seen two Polythemus moths in the last 3 days! In two different locations. One outside my fiance’s apartment, and the other outside of mine. Now, this is either the same moth following me across town (unlikely) or are these moths more abundant this spring?? I’ve seen these moths throughout my life, but never this many this frequent! Maybe like 1 every couple years, until now. I thought maybe there was a reason–climate change? wives tale? sheer luck? etc? Thanks!

  3. it helped me alot .
    i am also a nature lover like you :)

  4. Hi Seabrooke,
    Fellow silkmoth enthusiast here. I recently moved to Kingston and have been on the look out for the native silkmoth species. A friend gave me a female luna moth this summer and I was able to get eggs and raise them (I have six cocoons by me right now, one just wiggled!). I’m of course trying to get a hold of the other species so I can raise them and take pictures of their life cycle. Do you recall the types of trees you found these cocoons on? I know promethea moths feed on a wide range of trees, but often, there are regional preferences. Thanks!

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