Occasionally wild female moths are also taken at lights before leaves have fully burst forth.
"What can be done to delay caterpillar emergence from eggs so that food will be available at the appropriate time?" is a question I frequently get asked. I will address that question, but a more appropriate question with a more manageable solution might be "How can I have food ready in time for tiny caterpillars?"
It is important to understand that in the case of Saturniidae, eggs are not fertilized during copulation. Instead the male sperm is transfered to the female's storage capacity, and the eggs are actually fertilized at time of deposition when they are coated on exit with a mix of "glue" and stored seminal fluids.
A female can lay eggs for a period of three nights to as many as seven or eight days or nights. Since embryonic development does not start until fertilization, and since development times are fairly consistent under similar conditions, the eggs are likely to emerge over a period as long as their deposition period, i.e., eggs deposited on March 10 are going to hatch six days before eggs deposited on March 16 even though they have come from the same female. You might not have food ready for the "early depositions", but maybe you will have it for the "final depositions". There is hope.
The metabolic processes of adult Saturniidae slow down considerably when they are subjected to cooler temperatures. Adult lifespan can be increased by several days by placing the adult moth in an envelope or closed container and then placing same in refrigerator (not freezer). Removing the moth after three to four days will in all likelihood extend its life expectancy by a few days. Hence, a captured "early" female or a home eclosed early female, mated or otherwise, can deposit "good" eggs three to four days later, by cooling, than she would have had she not been cooled.
The metabolic processes of fertilized eggs are also greatly influenced by temperature. Although there are some Saturniidae species that lay eggs that diapause over the winter, the vast majority of Saturniidae species lay eggs that cannot withstand a freeze (maybe some can ???). Temperatures in the upper 30's F or 3-5 C apparently can be used to delay development by several days. I do not think a prolonged chill (beyond 4 days) will provide for a satisfactory development of embryos, but I hope to do some experimenting with polyphemus eggs this spring as per the notes below. I encourage members to also do some experiments and share their findings.
A combination of cooling the adult moth and cooling of subsequent eggs may result in eggs not hatching for as many as nineteen days after eclosion/capture of the adult. Perhaps this will give nature time to ready the foodplants. If not, maybe we can give mother nature a head start.
I have successfully forced indoor cherry and willow budding and leaf out to provide food for early Saturnia pyri (cherry) and Antheraea pernyi (willow) hatchings.
Many years ago I was sent some unsolicited Saturnia pyri eggs. In southern Europe this moth often flies in early to mid May, well before we have leafout here on Prince Edward Island. I did not anticipate I would have outdoor foodplant in time for the hatchlings.
I took a stroll and examined many young pin cherry trees. Most had buds that had swollen, but few were showing any signs of green leaves. There were a few, however, in somewhat sheltered locations, that were slightly more advanced than others. I took some stem cuttings (about twelve inches long) from the small trees that were furthest advanced and placed the cut ends of those potential hosts in a glass of water and placed them in full sun on a shelf in the living room.
Leaves quickly started to develop and I was encouraged by what I saw. After just a few days, however, the tiny fresh leaves wilted and dried. I was not aware of the importance at that time of enclosing the budding tips in a clear plastic bag to conserve moisture. Indoor air tends to be quite dry.
I learned enough though to get me through about a week's worth of feeding on forced stems. I simply went out and cut the stems a couple of days before I needed them. I continued to rear the larvae indoors on cut food in closed containers until there was sufficient outdoor food and low frost risk. I was able to get some cocoons. If I had not forced the cherry indoors, the larvae would have quickly starved to death.
On another occasion, I had received some Antheraea pernyi eggs very early in the season. There were no leaves on trees here at the time. A weeping willow tree showed the most advanced signs of swollen buds so I cut some longer stems (eighteen inches) and placed the cut ends in water. This time I enclosed the stem tips inside a clear plastic cover. Budding occured nicely and I think the young caterpillars were even eating some of the bud sheaths. I was able to offer the hatchlings greenish-yellow foliage while the outdoor buds remained unopened. I was gathering some of these stems one morning during a light snow flurry in May.
It is very easy to root weeping willow stems in damp soil. Enclosing the budding tips in something to retain humidity is important if the rooting is to take place indoors.
Small saplings can be dug up and transplanted to a large pot or bucket and brought indoors to force leaf out. I have used that technique with cherry and birch. Again cover the foliage to conserve moisture.
Here are my replies to a concerned "parent" from southern North Carolina.
March 8, 2008: "I had 2 more luna moths hatch and now I’ve got 2 that are coupling."
You are going to have lots of eggs so I recommend you do lots of experiments. Try a number of different foodplant cuttings. See which ones give the best results as far as leaf out goes, and then see which ones the caterpillars will eat. I would love to know and so would many other people. You are not the first person who has had early luna pairings this season. Sometimes cherries will leaf out. I have actually transplanted some small pin cherry saplings, as soon as the ground was no longer frozen, to large plastic buckets and also forced them indoors for food for a European spring flier, Saturnia pyri. I also took cherry cuttings and sprouted (not rooted) them indoors. It gave me an extra week and that was all that I needed.
Pretty sure the plastic cover to conserve humidity and keep buds from drying out is important.
Hope you can make something work.
One year my father was rearing Eupackardia calleta in New Jersey from eggs from southern Arizona.
The caterpillars were still feeding on privet into December. Foliage was getting tough and scarce so he called upon a couple of friends to ship him some stems with foliage from further south.
U.S. postal rates are pretty low so if you have a friend in Georgia or Florida and are really determined to make this work, you could try that. If all else fails you can get eggs for later in the season.
Keep track of date when you have suitable foliage outdoors and use that as a guide for next year.
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Congratulations on getting the pairings. Unfortunately you cannot extend the incubation period of luna eggs beyond 4-5 extra days without doing permanent damage to them (at least that is what I have been told). They are not like the eggs of Bombyx morii, the domesticated silkworm, which can be put into a state of suspended animation for several years by freezing them. I do not think these eggs would survive any freezing temps.
Cool temps, mid fifties to mid sixties would slow their embryonic development for a few days, but that is all. Normally at fairly constant temp of 68 F they hatch in 11-12 days. In summer if warm and humid (mid eighties) they will incubate in as few as eight days.
You are going to have baby caterpillars in 11-19 days.
The eggs are feritlized as they are deposited and the female will continue laying smaller and smaller numbers of eggs over a period of four to seven days. Maybe the eggs deposited on March 11-12 can be slowed to incubate for 14-15 days by keeping them relatively cool (mid fifties), meaning you will have some caterpillars emerging as late as March 27.
You also might want to try a couple little experiments to force budding and foliage development.
I suggest you try the following:
1) Locate a weeping willow tree (buds open early and good food for lunas, polyphemus, cecropia).
2) Cut three branch ends about eighteen inches long.
3) Strip the little buds from the bottom six inches of the cut ends.
4) Get a pop (soda) bottle or some other container that you can fill with water.
5) Put the cut ends of the willow stems into the water.
6) Put a large, clear, inflated plastic freezer bag, or some other clear cover over the top of the cutting tips. Cover all twelve remaining inches if you can and tie the bottom of the cover closed around the base of the stems just above the water level.
7) Keep the apparatus in the house at indoor room temperature to try to force the buds into opening and some leaves to form.
Willows can actually be rooted this way. The cover over the ends you hope will produce leaves is to keep the buds from drying out in the indoor air. This cover should be airtight to maintain a high humidity inside the bag/cover.
Hatchling caterpillars do not eat very much for the first few days. You might be able to get enough foliage to feed them until nature starts producing enough food for them.
If you want to actually root the willow, use a container with a wide moth (plant potting container, large tin can, quart milk continer etc., and use potting soil, peat moss, sand or a mix of all three. Saturate the medium with water and stick in the stems, again about six inches deep.
You can try putting the eggs into cold storage to see how long you can delay them.
1) Get some ziploc plastic tubs or gladware sandwich sized containers. Put some eggs deposited on different dates into the different containers and record date of deposition on each container.
2) Put containers, lids on tight, into refrigerator (not freezer).
3) take some eggs out of cold storage after two days, some after three days, some after four days, etc. and see how long you can delay emergence without killing the eggs.
I probably will try this myself with some polyphemus eggs this summer to see the results.
I would love to learn what you find out.
Best of luck.
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If the willow buds open and develop leaves, you may want to start another group of stems every third day until natural food is available.
You can also try the pussy willow, but I don't think it will be as effective as weeping willow.
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Importing cut foliage from further south is also an option for early season "headstarts". Cut food in a closed freezer bag can be stored in fridge crisper for a week or too, just like lettuce. Leave the foliage on the stems.
I would very much like to publish other accounts of what works to extend the season on either end. I would also like to know what anyone else may discover regarding refrigeration of non-diapausing eggs.
Send comments to Bill Oehlke.
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Dan Zieher writes, "I have tried your chilled ova experiment with some success. The species was Saturnia walterorum. I had the ova refridgerated about 10 weeks. However, I had about 60 % mortality. I was unable to get the larvae past 3rd instar... I live in WI, and even "pushing" Staghorn sumac, the food plant just does not quite have the right timing." Saturnia walterorum is an early spring species from California. Even under "normal" conditions larvae can incubate for at least as long as thirty days. I am hoping many of you will experiment with excess eggs and report findings. I am really surprised that eggs would hatch after a seventy day chill. We cannot tell if Dan's larvae died prior to maturity due to deficiencies caused by the long storage or if there were other factors.