imperial moth

Asked September 24, 2015, 10:52 AM EDT

i found a imperial moth in the instar fifth stage...I guess this is what it's is large green and yellow...I made a home for it using soil from the yard with some potting soil about 5 inches deep so it can burrow down ...yesterday it burrowed itself but this morning it came back up and is just moving around the container as if it wants out...what am i doing wrong...i am new at this and don't want to cause the imperial harm or to cause it to not want to burrow.
The container i have it in is about 8 inches around and made of plastic. The soil is soft enough so it can burrow.. I also put on top some oak, maple and sweet gum leaves so it could eat...but not sure it eats at this stage of it's life...I did some reading about imperials but need your help so i can make a good habitat for it to become an adult moth.

Wake County North Carolina

5 Responses

I have only tried to rear imperial moths once, and managed to get a few of them up to about 4th instar before unfortunately, they all died out. For mine, the problem was not enough humidity for them to develop properly. So I can't comment from my own experience as to the behavior of your larva. However, I have located an article posted on the internet that discusses rearing silk moths. I have included a link at the bottom to the complete webpage, however, here is the pertinent part excerpted from that webpage regarding the conditions for imperial moths to pupate.



Regal and imperial larvae do not make cocoons - they burrow into the ground, and need different treatment (below).

Give imperials & regals about 6" of moist peat moss to burrow into, where they will pupate. Peat moss, which is fairly germ-free, seems better to me than soil, which is not very clean. Avoid vermiculite and other materials that are too loose/coarse to hold their shape. If the little cave that the larvae has dug collapses on it, the animal can get deformed when it molts into a pupa.

Even if there is nowhere to dig into, the larva will eventually pupate anyway. Thus, you can also just put the larvae in a container with damp paper towels and let them pupate in "the open". Make sure there is humidity. This is a good way to observe the molting, which is strange to see.

After they dig in, you should wait at least two weeks before disturbing them, since they may still be soft under the ground. The caterpillar molts into an egg-shaped pupa that first is greenish, then turns dark brown and hardens.

Their winter care is something of a pain. My friend had nearly all of his rot over winter for several years until he discovered how to keep them. He stores imperial and regal pupae in the frij, in a special Tupperware arrangement. (If pupae sit in the open in a frost-free frij they will dehydrate and die.) Get a piece of 100% linen
(avail at bridal stores). Linen will not get wet in damp air. Lay the linen over the top of the plastic container like a hammock (the closed lid will keep it from falling down). Put a small amount of water in the bottom of the container, suspend the pupae in their hammock over the water, and close the lid. The linen does not get wet, but the air is kept humid. I open the container every two weeks, check the water level, and blot up any condensation on the lid or pupae. This system should also work for other species. My friend does not put air holes in the container. However, I fear that they could eventually suffocate if sealed up for too long. So I open the container every so often. Or you could put in some air holes.

Regal and imperial pupae can take freezing temperatures in the frij, but not for very long. Keep the temp above freezing. When it gets cold outdoors, that is the time to start the pupae's cold period. They need to be acclimated to cold. Keep them somewhere where they will gradually get cold over a period of at
least a week, as it does outdoors, before putting them in the frij. In spring, take them out of the frij whenever it warms up outside, and put the pupae back into peat moss, in a flowerpot, inside a cage, outdoors. I water it often enough to keep them from drying out. The adult is able to crawl out of the peat when
it hatches.

To see if a pupa is alive or dead, carefully poke it in the leathery area between two abdominal segments with something dull like your fingernail or the edge of a piece of paper. They hate this; live ones will squirm. Other clues: live ones weigh more (they sink in water) and are glossier than dead ones.


The person on this website has apparently had very good luck rearing silk moths so following these guidelines could help if your caterpillar is still wandering. However, in the time since you submitted this request, it is possible that your larva has settled down and burrowed back down into the soil you provided for him. Hopefully, the comments provided will help you get your caterpillar successfully pupated and the adult emerged next spring. Good luck!

Thank you for your caterpillar finally went into the soil two days ago....I put in deeper soil to about six inches and that was acceptable. I mixed peat and yard soil... the article you sent me was so very helpful and it gave me all the information I needed...

Thanks for your help.

TJ Gentry

Hi again, I have taken your advise before and you sent me great info...I now have another question...I put my Imperial moth ( it is in the hard brown stage) into the frig as recommended in a Tupperware container on a piece of 100% linen made into a little hammock over a small amt. of water and closed the lid...I do check on it and it seems to have some weight to it and is glossy...But when I try to get it to wiggle by touching the abdomen there is no wiggle..My frig. is set to 38 degrees and I did let it get use to the cooler weather before putting it into the frig..
Is it because it is in a dormant state and will not move? or have I killed it....I sure hope not...I so would like to see it come out this Spring as a beautiful moth...
Any help would be greatly appreciated.

The fact that you indicate the pupa still seems to have some "weight" to it and is glossy suggests to me it is probably still alive. Dead pupae tend to dry out and become much lighter and duller, or in your little greenhouse box might start to mold. I suspect that it is not moving because of the cold temperatures. Most insects as adults and larvae become very inactive at temperatures much below 50 degrees F. I would suspect this normally holds true for the pupa stage as well. It is just too cold for its remaining muscles to "wiggle". Basically it is in sort of a state of suspended animation, which we call "diapause". While at the cold temperatures it cannot develop much at all. And in many cases the pupa actually has to go through a period of cold or it cannot complete its development. This is more common in species that live in the north. Most of the development and transformation to the adult moth will actually take place next spring once the temperatures get above 50-55 degrees F. and remain there for prolonged periods of time. Each species of overwintering insect needs a certain number of "degree days" above a specific temperature threshold to complete its development. At temperatures above the threshold, development can take place. Below the threshold and development pauses. It probably would better be called "degree hours" since it really amounts to a total number of hours above the threshold temperature. So for each day in the spring, when temperatures may only be above the threshold for a short time, only a few "hours" accumulate. As the days stay warmer longer, more hours accumulate, and by early summer, the entire day may be above the threshold and development can go on rapidly. I don't know what the specific number of degree days/hours are for the imperial moth but it likely amounts to many weeks. So even though the temperatures warm up in the spirng and it can start the transformation, it still takes a while and these moths don't normally emergte until early summer. Of course a warmer spring may let them emerge earlier, and a cooler spring may prolong their emergence until later. After a couple of months in the refrigerator, you could probably pull this pupa out and leave it at room temperature and it would start its transformation. However, it would likely then emerge early in the spring, when it would be too cold to release it outdoors, and it would not have any mates around. If you plan to realease it next year after it emerges, I would keep it in the refrigerator until around March before beginning to warm it up. As per the previous instructions I sent, it should then be buried back into the peat moss while it finishes developing. When the adult emegres, the act of digging its way to the surface helpe to pull its soft wings out. And make sure you have some vertical twigs, a piece of bark or some other object for it to climb onto so its wings can fully hang down and extend before drying. Hopefully, it will come through fine.

Thank you so very have put my mind at ease...I will follow your advise to the letter...and come next Spring after March here in NC..I will put it back into the soil and watch it emerge as a beautiful Imperial moth..

Thanks again,
TJ Gentry