Cecropia Moths Raised from Eggs

2013 July 24

And here is the second posting for National Moth Week. It was over a year in the making, so it will be kind of long.
On May 28, 2012, we were visiting some friends who have a small farm a few miles northeast of us, and while Sandy was admiring their apricot tree[1], she saw these four eggs on a leaf that she thought looked interesting. That’s a metric ruler next to them, and the marks are 1 millimeter, so the individual eggs are about three millimeters long. There are a lot of insects that are smaller than this as adults, suggesting that whatever these are will be pretty large.

I was excited about these, because I was pretty sure that they were eggs of some type of Giant Silkmoth. This was backed up by the pictures of Cecropia Moth eggs (Hyalophora cecropia) in “Tracks and Signs of Insects and Other Invertebrates”[2], which looked practically identical. Sandy must have found them almost immediately after they were laid, because they took close to two weeks to hatch. By June 10, they had hatched out into these little black spiky caterpillars (hatchlings are referred to as “first instar”).

I fed them plum leaves, which is reported to be one of the best foods for Cecropia caterpillars, and they liked them. By June 19, they went through their first molt, becoming the “second instar” caterpillars that were yellow things with black spikes.

Young caterpillars are touchy to raise, they are so small that they are subject to drying out. They also are susceptible to diseases. One of the four had always seemed stunted compared to the other three, and right around this stage it died and its insides liquefied. Luckily, by that point I had separated them into individual rearing containers, so if it was a disease the others didn’t have a chance to catch it. I was using the semi-disposable Ziploc sandwich storage containers, and swapping their old leaves for fresh ones every day when I cleaned out the containers. Note that they were not in the classic “jar with holes poked in the lid”, because that never worked for us when I was a kid – they always dried out and died.

The three survivors had gone through the second molt to the “third instar” by July 8, with another color change. By this point, they were developing the distinctly colored tubercles on the back that are characteristic of cecropia caterpillars.

The third molt had occurred by July 26, and by this point the “fourth instar” caterpillars were getting to be quite large. The color of the tubercles was quite pronounced. Their appetites had also become considerable, and I transferred them to one of the foot-square mesh cages and started feeding them whole plum branches instead of individual leaves (with the branches in a vase of water to keep them green and fresh).

They had gone through their fourth molt to the fifth instar by August 6. Or, at any rate, two of them had. The third one had a bad molt, couldn’t get out of its skin, and died. It is possible that this happened because the air wasn’t humid enough. At any rate, by this point the two survivors were huge, and were stripping all of the leaves off of a plum branch with about 20 leaves every day. This next picture is in Sandy’s hands:

And this one is on my hand, with a quarter as an additional size reference.

The tubercles on these were actually about the same size as the tubercles of the previous instar, but the caterpillar is so much bigger by this point that the tubercles now look kind of tiny.

After eating like crazy for a bit over a week, they started making cocoons. One of them made a cocoon out of the end of a tree branch – here it is with the second one crawling over it.

The second one I was a bit worried about at first, because it started looking discolored and oozing a brown liquid, and I thought it was dying. So I opened the cage to look at it better, and neglected to close it again. And during the night it crawled off. I eventually found it in a cardboard box, where it had just started spinning a cocoon. There was an electrical cord running across the box that had gotten tangled up in the cocoon, but I was able to get it out early enough that the cocoon finished up OK.

The cocoons started out white, but gradually turned brown until they were about the color of dead leaves.

At this point, we needed to overwinter them so that they would emerge in the spring. I particularly wanted them to emerge at the same time as other cecropia moths, because if at least one of them was female, then I’d be able to use her to lure in males, breed them, and then get a stock of eggs for rearing more. So I put them into the mesh cage along with the Polyphemus cocoon described last time, and put the cage into the cellar entrance to our old house.

Then, at the end of the winter, I pulled the cage out of the cellar and put it in a protected spot near our front door. And on June 24, both of them emerged nearly simultaneously. And yes, they were definitely cecropias.

One of them had somewhat lopsided wings (here it is on Sam’s hand)

while the other was slightly bigger and more symmetrical.

Their bodies were brightly colored in white and red, and very fuzzy.

Unfortunately, my dreams of breeding cecropia moths were dashed, because they both turned out to be males, with the big, fluffy antennae.

So, we let them go. The unsymmetrical one seemed to be able to fly just fine, so maybe they both found a nice female cecropia to mate with.

[1] Those of you keeping track of our climate up here might be thinking, “But you can’t grow apricots up there, can you?” This is true. We (meaning Sandy and me) can’t. Tony evidently can, but he puts in a phenomenal effort with his plants, and gets correspondingly impressive results.

[2] “Tracks and Signs” is a great book. It specializes in all the things related to insects that aren’t commonly included in other guides, like eggs, cocoons, shed skins, galls, characteristic damage to plants, and tracks in sand or mud.

7 Responses
  1. July 24, 2013

    This is an amazing post. It was almost like writing a book in terms of the time frame. The caterpillars look like stuffed socks with decorative pins stuck in them. The patience you display in feeding these voracious creatures is also admirable. I would have got bored and put them outside (if I had ever taken the eggs in for fostering in the first place).

    I really like this life cycle post. Can you do more post like them? Can you set up a nursery for slugs? I have a garden infested with them and I’ve always wondered how they breed and grow; they seem to arise on the Petunias and sunflowers by spontaneous combustion of some sort.

    The moths are even very pretty (for bugs).

    Again the lack of antipathy to having vile creatures as pedestrians over the wrists, hands and arms of the author is alarming but certainly a salutary example of what can be achieved with close contact with bugs in this manner.

    What does a female Cecropia moth look like? Do they simply lack those moustache-like antennae?
    It is a shame you could not set up a foster care system for abandoned Cecropia moth eggs. But at least you got one set of babies out the door –a 50% success rate with kids is pretty good. Isn’t it amazing what comes out of an egg?

  2. July 24, 2013

    Thanks, Julie!

    I like doing these life-cycle posts, and whenever one works out I post it. It does take some time, though, and a lot of the time they die without maturing, so there will always be more of the one-shots. A good place to find full bug life-cycles is http://www.buglifecycle.com/, which is sort of a central clearing-house for this sort of thing.

    We could try doing a life-cycle for slugs, we find the eggs under rocks pretty regularly.

    The female cecropias are bigger, and have significantly smaller and less fluffy antennae, but otherwise look about the same.

  3. Carole permalink
    July 24, 2013

    What a wonderful find resulting in an exceptional post. Thanks.

  4. jrr permalink
    August 20, 2013

    Awesome post! Thanks.

  5. Linda Hudak permalink
    August 21, 2017

    I found what I beleive is a Cecropia Moth catapillar starting to form a cocoon. We are cutting the tree when we found it so we put it into a container. When I was reading that you needed to overwinter them what exactly did you mean? We want to take care of it best that we can?

  6. August 22, 2017


    They evidently need to go through a period of cool (maybe near-freezing) temperatures, followed by warming, to trigger their development to a moth. What has worked for us is, we have an un-heated entryway to a cellar. We just put the moth down there in an insect cage, elevated off of the floor so that it wouldn’t have moisture on it that might lead it to get moldy. Then, when it got warm enough outside that the snow had melted, we moved the cage up to a protected spot near our front door, and waited for it to come out.

    If you don’t have access to an unheated cellar, I’ve heard of people basically making one by digging a hole, suspending the cocoon in the hole, and then putting a board over the top (this only works if you don’t get so much snow that the hole would flood in the spring), or just putting the cage in an unheated garage.

    For that matter, some people say they get good success by putting it inside of a freezer baggie (with plenty of air space) and storing it in the crisper drawer of their refrigerator until spring.

  7. Tayden permalink
    June 3, 2019

    my cecropia moth caterpillars erent growing!

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