I replied, ``Actually, the caterpillar hasn`t made a silken cocoon. Most of the earth pupators (Sphingidae, and Saturniidae from subfamily Ceratocampinae)
dig down into the soil and excavate a subterranean chamber in which to pupate. A few species use flimsy strands of silk to bind some leaf litter at the soil surface, but most
go underground anywhere from one inch to six inches deep.
``I suggest you leave the caterpillar where it is for at least a week; ten days would be even better. Usually such caterpillars will shed their skins one last time to form a
dark structure called a pupa. The outline of the moth eyes, antennae, wings, body can be seen on the pupal shell.
``A fresh pupa has a very soft structure and can easily be damaged by handling. After a few days the pupal shell will darken and harden. At that time gentle handling will
usually do it no harm.
``In northeastern Texas, imperialis larvae (caterpillars) that are found in late summer - early fall usually form a pupa that is in a diapausing (hibernating) state.
Under normal conditions outdoors, where day lengths are typically getting shorter and temperatures are getting cooler in the fall, the pupa would remain dormant until the
longer, brighter, warmer days of spring arrive. If your spring days were warmer than normal, then you might expect to see the moth emerge in late April or early May.
On average, there would be a flight in mid to late May into early June in Texas. Eggs and larvae and pupae from that first moth flight would emerge as adult moths July-August
in a second flight. Eggs from the second flight would have larvae feeding into October, pupating in October-November, and emerging as moths the following spring.
``Since there are two annual flights of imperialis in Texas, we say that the species is bivoltine in your state. In southern Alabama and Florida, the species sometimes
produces three broods each year (trivoltine). Where I grew up in northwestern New Jersey, the species is univoltine, only producing a single brood each year.
Had you found a mature imperialis larva in June-July and it pupated in the aquarium, I would have suggested you let it remain there, and would have predicted
a moth would emerge in late July- August - early September, anywhere from three to five weeks after pupation.
Now, however, you are faced with a bit of a dilemma. Due to the amount of daylight this caterpillar experienced, its body would have produced enzymes that would typically
put it in a diapausing pupal state where normal changes, development would not occur until hours of daylight begin to increase (late December) and temperatures again begin to
warm (Spring).
Once development starts, its pace is determined largely by temperature.
``Inside your house, even under earth in the aquarium, this pupa is going to experience artificial light and temperatures that would be warmer than outdoors. If left where it
is,
I would predict the moth will emerge in January or February when it would be too cold outside for the moth to be released. If you wish to keep the moth as a specimen, the
winter
emergence would be fine.
``If it is your intent to release the wild moth, then you want it to emerge (eclose) in May-June. To make this happen, you need to follow the following suggestions:
1. On November 10-11 gently dig through the soil in the aquarium and unearth the pupa.
2. Get a sheet of toilet tissue and place the pupa in one corner so its length is perpendicular to the diagonal of the sheet. Roll the sheet with the pupa inside so that
tissue extends on both ends beyond the ``head`` and ``tail`` ends of the pupa.
3) Moisten the extensions of the tissue sheet and gently twist them closed so that you have created an artificial chamber for the pupa.
4) Get a sandwich-sized tupperware, gladware, etc., plastic tub. Put a folded paper towel on bottom of tub. Put one or two drips of water on the paper towel.
Put the pupa, rolled in the toilet tissue in the plastic tub and put the lid on tight. There should be no air holes in the tub.
5) Now you need to store the pupa in the tub for the months of November-April. It should be kept relatively cool and in a dark place. The ideal place for storage, I have found,
is the refrigerator cripser. However, if that is not an option for your family, a cool spot in the basement or in an unheated shed or garage will probably also be fine.
The one or two drips of water are necessary to maintain a proper humidity to keep the pupa from desiccating (dehydrating). The diapausing pupae does not need much oxygen so no
air holes which might allow moisture to escape.
6) In the spring, probably early April, depending on local weather, you will bring the pupa out of cold storage and let it develop in a proper emergence cage. If you write back in
early April, I will describe the final process for you.
``A trick I have learned for dealing with the earth pupators, which simplifies the process a bit, is to place the larva (caterpillar) directly into the plastic tub
when it is done feeding and starts crawling around bottom of jar or tub. The caterpillar will usually crawl under or between the layers of paper towel in the tub
and will pupate there in four to seven days at room temperature. Then you don`t have to worry about injuring it when it is time to unearth it, and you will be able to see when
the pupa has been formed.
``Many wild caterpillars have been infected with parasitic wasps and flies. These parasitoids are harmless to humans, but it is possible that your caterpillar has been infected
and that no adult moth will emerge. Instead, all that will emerge from the pupa is the parasitoids. I cannot see any entry wounds on your caterpillar so I think you have a good
chance of seeing
a beautiful moth in the spring.``
