raising Imperial Moth caterpillars

Asked July 26, 2014, 8:55 AM EDT

I found a female imperial moth, turned out to be fertile. She laid 100+/- eggs (before I released her) which hatched about a week+ later. I've raised cecropia, polys, & prometheus many, many times since grammar school (40 years ago). These were the largest & most active 'babies' I'd ever seen. Problem is, they wouldn't feed & I lost them all. I had them in a plastic container (clean) w/a cheesecloth cover, 2-3 types of oak & pines in there as well as walnut, cherry & willow 'just in case'. Some seemed to be spinning a little silk. They just wandered around until they dried up, maybe a couple dozen 'poops' in the bottom of the container. Any idea what went wrong??

Will County Illinois

2 Responses

I have only tried to rear imperial moths once, and managed to get a few of them up to about 4th instar before they all finally died out. I also experienced fairly high mortality among the first instars. My guess at the time was possibly low humidity, but I wasn't sure, since some were feeding and growing normally. It may be that they are just more difficult to rear than other species. I looked on the internet and found the following website which talks about rearing the young larvae of saturniid moths (I have also copied it below). You might compare how you reared yours to that article to see if anything stands out. The article suggests that the 1st instar larvae should be kept in a closed container to keep the humidity high. Since your container had an open top, low humidity might have been the problem. Hopefully, you can find another female some time and try again. Imperial moth caterpillars with all their spines and spikes and color variations are very cool caterpillars. You might also try more extensive searching on the internet to see if there are any more posts about someone successfully rearing imperial moth caterpillars specifically.


Young larvae

The main problems with just-hatched larvae are that they
sometimes crawl off their food before they begin to eat, and they
can dry up and die quickly. To prevent these problems, I keep
them in a Tupperware-type plastic container with the lid closed.
Put a sheet of damp paper towel on the bottom and lay the leaves
on it. Use leaves that are mature, but not old and leathery; do
not use young new leaves. This arrangement makes it easy to keep
track of the caterpillars, and keeps them close to their food.
The humid air keeps the leaves alive and the larvae from drying
out when they are very small. Once a day (twice is better): empty
the container and rinse it, replace the paper towel with a new
one, rinse or knock off any droppings stuck to the leaves or the
larvae, and replace errant larvae on the leaves. (Never pull
larvae off the paper towel, though - instead cut out the little
piece they're on.) Adjust the amount of water you leave in the
towel, so that when you close the lid, the environment inside the
container will be humid but not wet. Make sure the larvae
themselves are not wet. Excessive dampness promotes disease.

I keep larvae in this container until they have molted at least
once. You can tell if they've molted because in most species they
change color and appearance with each molt, and because the head
capsule is much larger at each new stage ("instar").

You may want them to switch to another food plant species partway
through their development. Sometimes this can be done, and
other times they will refuse to switch. Put them on the new kind
of food, replace them if they walk away, and watch closely to be
sure they're eating it. An ideal time to switch foods is right
after a larva has molted, before it gets started on the old food
again. At this time it hasn't eaten in a few days and is

Humidity - that had to be it. In the past I've 'kept the lid on 'em' only to watch mold or disease invade the population. This time I went too far in the opposite direction. This is much later in the season than I've previously encountered fresh eggs, typically I have had hatchlings in mid-June before the much drier late July days. Perhaps the answer is a cheesecloth lid and mist w/ water a couple times a day. Thanks for the info!