Overwintering Cocoons and Pupae

Here on Prince Edward Island, Canada, I overwinter all breeding stock of indigenous Saturniidae (silkmoths), Ceratocampinae (Anisota and Dryocampa: regal moths) and Sphinigdae (hawkmoths) in ziploc plastic tubs in my refrigerator crisper compartments. The tub lids are on tight, there are no breathing holes, and for the most part no moisture is put in with cocoons. The crisper compartments, where a normal person would store lettuce, celery, cucumbers, etc., remain at a fairly constant temperature of 35-40 F. (2-5 C)

For the Sphingidae pupae and Ceratocampinae pupae, I usually put two or three paper towels on the bottom of the quart-sized containers and add (literally) two drips of water, so little water that you would hardly know that it is there. I then add another layer of one dry paper towel and insert about 10-15 naked pupae. Another paper towel covers the lowest layer of pupae and I continue building layers of paper towels (dry) and pupae until the container is full. The lid is snapped shut and in late September the container goes into fridge crisper or into a mini fridge which also remains around 38 F (3-4 C) .

In the minifridge I have an aquarium thermometer which you can usually pickup for under $2.00 at a pet shop , just to keep an eye on temperature. I inspect the pupae and cocoons about once every 1-2 months just to make sure there is no mold or mildew forming. I do not mist cocoons or bathe pupae. I actually discourage such a practice as the extra moisture can cause problems.

Most silkmoth species from areas that encounter freezing temperatures can be handled as described above: Actias luna, Antheraea polyphemus, Automeris io, Callosamia angulifera, Callosamia promethea, all of the Hyalophora species (columbia do not need to experience a freeze as is so often reported in texts), Samia cynthia.

Silkmoths from more southerly regions where frosts are not normally encountered, definitely should not be exposed to artificially induced freezing temperatures.

Citheronia regalis and Eacles imperialis can be stored as indicated above for the Ceratocampinae and Sphingidae. Earth pupators from more southerly regions where temps likely would not dip below 40 F., can be stored in an unheated basement or in a mini fridge that doesn't drop below temps they would normally encounter.

I begin taking my cocoons out of cold storage in late April or early May. The cocoons are put into hardware cloth cages (11" x 11" x 24") that have 3/8 inch mesh. A few layers of paper towels are put on bottom of cage to absorb fluids released during eclosions or to absorb metabolic wastes discharged by emerged moths. The cages are kept indoors at fairly constant temps of 65-75 F. Moths begin emerging in late May.

In New Jersey, my father, Don Oehlke, stores his cocoons (breeding stock) in an outdoor, roofed, screen enclosure, where the cocoons are exposed to rains, snow, warm spells, etc.. His cocoons tend to eclose at same times as indigenous stocks. I do not encourage outdoor storage of cocoons unless you are sure that the enclosure is rodent proof. I have heard of too many horror stories where cocoons stored in outdoor sheds or in other outdoor enclosures become food for chipmonks, skunks, shrews, etc.. Birds will also peck at emerged moths in outdoor cages. A fine screen is needed for protection.

Here on Prince Edward Island, I know how long cocoons need for development once they come out of storage and can pretty well time my eclosions to coincide with local flights.

For the naked pupae of the regal moths and hawkmoths, I offer a more humid emerging environment: wet paper towels are put on the bottom of a 3-5 gallon plastic tub, a layer or two of bubble pack is placed over wet towelling, a couple of layers of dry towelling are placed over bubble pack, and naked pupae are placed on top of dry paper towels. Paper towels are draped top to bottom over sides of plastic tub so moths can climb and inflate. The lid is on tight to maintain humidity. I also keep these plastic tubs indoors.

If you live in an area where indoor air is very dry or where your refrigerator might have exceptionally dry air, then you might want to mist pupae or cocoons periodically after they come out of storage or you might want to add a few drips of water to paper towels in cocoon and/or pupae storage tubs. Outdoor air does tend to be much more humid than indoor air, especially during cold weather. I would avoid wetting cocoons though unless they also have ample opportunity to dry thoroughly.

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