Giant Silk Moths

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Giant Silk Moths

The largest moths of temperate North America are known as Giant Silk Moths, family Saturniidae. These moths emerge from their cocoons in June in what are knowns as flights, live only long enough to mate and lay eggs and then die. They have only rudimentary mouth parts and eat nothing during their short lives.

The eggs are laid on the favored food plant and hatch out in a few weeks into the caterpiller form (silk worm). After feeding and growing for a few weeks, they spin silky cocoons on twigs and spend the Winter maturing and waiting for the flight in Spring.


This week's story starts in Fall when we found this large cocoon attached to a branch of a silver maple tree.

We broke off the twig and placed it in the bughouse for the Winter.

In June, this beautiful Cecropia Moth, emerged from the cocoon.

Much to our consternation, it seemed totally incapable of flight. When pushed off Marilyn's hand, it dropped to the ground like a stone and this situation did not change after several days. Instead of abandoning it to fate, we hung the bughouse (with the door removed) from a branch of the tree where it was found and hoped a male would follow the pheremone trail to fertilize this female.

According to published information, males can detect gravid females from a distance of a half mile or more.

About a week later, she laid a cluster of white eggs and died.

The eggs never hatched so we assume she never found her man.


Walking through the woods with a flashlight, I spotted this beautiful Luna moth hanging on a twig near the ground. My first reaction was to run back to the house for the camera but that usually ends up with a camera and a vanished subject.

I found that breaking off the twig and lifting it didn't seem to disturb it so I carried it all the way back and put it in the "bug house". In the morning, I took some pictures and then released it where I found it. Much to my surprise, it still showed no indication of flying or moving much at all.

After dark, I went back with a light and was amazed to see it flying straight up and down as if it were on a 15 foot string. I presmue (as it was a male), that this was it's arial cortship display although I have never heard this behaviour reported.

The Luna Moth lays it's eggs on the leaves of hickory and walnut trees which we have many of in our woods.

The mature "silk worm" spins it's cocoon around itself but always attaches leaves to make it less conspicuous to predators. How it does this while spinning itself inside would be interesting to see. The result is a rather messy looking affair but survival is the issue, not silk stockings.

You can see a bit of the silk in the upper left of the cocoon.

NOTE: The Audubon Field Guide to NA Insects states that the Luna is an endangered species but I do not think this is correct in the legal sense of the word. It certainly is rare and in danger of going the way of most beautiful things in nature due to the onslaught of human overpopulation.

Imperial Moth

Eacles imperialis

Gordy (our goat) was sniffing the ground in the woods one day clearly trying to make sense out of something. When I went over to look, I found this beautiful moth had caught his attention.

The Imperial Moth lays its eggs on the leaves of deciduous trees upon which the larvae feed. It pupates in the soil and the moth emerges between June and August.

It is a member of the Giant Silk Worm family (Saturniidae).

I am not sure I can read anything into this but in the shade, the edge coloring looked purple and this could possibly have some connection to the common name, as in imperial purple.


Callosamia promethea

Also known as the Spicebush Moth, the Promethea was used as a substitute for the Giant Silk Moth but was never commercially practical.

In addition to Spicebush, the larva feeds on Sassafras, Tulip Tree and Wild Cherry.

In case you wonder about the pin through it's body, this specimen was found dead in the neighbor's driveway so we added it to our collection. Giant Silk Moths are too rare around here to kill for collections.

The cocoon in the above picture was spun in situ by this larva found in the pasture. I set it on the gray background to take a picture and then covered it with a small bowl to keep it from leaving while I processed the picture.

By the time I came back to release it, it was firmly attached to the wool background and to the bowl so we left it to complete it's mission.

In the morning, we peeled the bowl off but it is going to spend the Winter on the board.

Hopefully, we will have a live one to photograph in Spring.

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