Mark Young recently sent me a request for some information. He wrote, "Do you know where I can find a timeline for Luna and Polyphemus larvae? I was unprepared for the Lunas to essentially molt twice in four days - I thought they were rejecting the food source."

I'm going to respond here to Mark's request and also offer some observations on factors which seem to affect development times not only for larvae, but also for eggs and pupae.

Eggs: Here on Prince Edward Island in eastern Canada most Saturniidae (single brooded here) fly from late May until very early July with most peaks from mid to late June. I place my wild captured and/or "reared and paired" females in brown paper sandwich bags for egg laying. The bags remain indoors where average temperature is between 65 and 68 F during the day and slightly cooler at night. I live in the woods and the house is sheltered by trees on all sides so it is not heated much by sunlight even on warm, clear, sunny days.

My observations over a number of years are that luna and polyphemus eggs usually incubate under those conditions for twelve days. Cecropia and columbia usually also take the full twelve days, but sometimes require a bit more time.

I grew up in rural New Jersey (Pottersville, Hunterdon County) where polyphemus and lunas are usually double brooded and sometimes even produce a partial third brood. I have seen summer brood (late July to early August) Saturniidae eggs complete incubation periods in eight to nine days when indoor temperatures often got into high 70's or low 80's F.

Hence the first clue that temperature is going to influence development time.

When is too much warmth detrimental? I do not know specifics, but I do know eggs can literally be cooked/killed if they spend time in an envelope in an outdoor mailbox exposed to full summer sun or even in a porch mailbox with southern exposure. If you order eggs to be delivered by mail, it is usually best to provide a post office address unless you are sure you or a designate can check mailbox before temperatures climb too high.

Larvae: Here on P.E.I. my luna larvae usually take between five and six weeks to develop (emergence from egg until beginning of spinup = 35-42 days). Polyphemus get larger and take longer, usually six to seven weeks.

The latest I ever saw a wild female polyphemus here was July 10. I attempted to rear larvae from the eggs she deposited and found that I still had larvae feeding into early October (ten to eleven weeks after emergence from eggs). The generally cooler daytime time temperatures and the much cooler night time temperatures one experiences on P.E.I. starting in early August greatly slow development time.

I was shocked to read (email replies) that luna eggs I had shipped to California and Florida took only nineteen days to go from egg-hatching to cocoon spinning.

In some cases these larvae were being reared outdoors in sleeves in warm humid environments. In other cases, the larvae were being reared indoors in plastic tubs or glass jars, but again temperatures were warm (almost constant) and humidity was high.

Several years ago, Vernon Brou from Louisiana set me an article he had written about lunas in his home state. Vernon indicated, based on his extensive collecting over a thirty year time period, that there were at least five peak flights in Louisiana each year with highest peaks at 36 day intervals.

If you allow one/day night for pairing, eight days for egg incubation, and ten to twelve days for pupal stage, the larval period is only fifteen to seventeen days.

Here on P.E.I. when my larvae are ready to moult into third, fourth and fifth instars they stop feeding for almost a full day. Obviously, when surroundings are more humid and warmer, the larvae discard clothes like a teenager preparing for a date.

Some research has indicated that larval hormonal changes are influenced by the photo period (hours of daylight or even artificial light) the larvae experience in fourth instar. I have had people tell me that luna eggs from here reared indoors (high 60's-low 70's) with extra light took almost as long to mature to spinning stage as they would here, but, instead of going into diapause for the prolonged winter the pupae would experience here, the moths emerged from cocoons fourteen to eighteen days later.

There are some Saturniidae larvae that are primarily night feeders, some that are predominately daytime feeders. Hence larval development times are probably going to be influenced by temperature, photo period, and probably relative humidity as it influences the amount of moisture content in foliage.

Pupae: In the late 1990's I was rearing thousands of Antheraea polyphemus each summer to supply a major pheromone research project in Germany. To try to spread the rearing out as much as possible, I was bringing in eggs from more southerly locales to get a head start on the breeding/rearing season. I could have eggs hatching in mid May just as leaves were filling, rather than having to wait until late May-early June for the local flight.

Those "head-start" larvae spun cocoons in late July. It was important for shipping purposes to make sure the larvae had pupated and pupae had hardened before shipping.

I harvested cocoons daily as they were spun up, brought them indoors and placed them in a small spare bedroom with a space heater to hasten the process. As soon as I had over one hundred cocoons ready for shipping, I literally glued the cocoons to the bottom, sides and bottom-side of the top of a cardboard box with enough room between the cocoons for emergent moths to escape and have enough room to hang and inflate properly inside the shipping box.

The cocoons were then shipped regular airmail from Montague, Prince Edward Island, Canada, to the Max Planck Institute in Germany. The packages usually emerged within fourteen days (four days for pupation, ten days of shipping) from spinup date. A few early spinners would sometimes emerge in transit, but the live moths were still fine for the project.

These "summer" polyphemus cocoons reared on P.E.I. would usually emerge about fourteen to sixteen days after spinup. Under even warmer conditions, I have heard of polyphemus emerging after only ten or eleven days after spinup. I was always glad when the first few early batches were done and I could send diapausing (overwintering) cocoons, ones that were spinning up here mid August or later.

It was interesting to me to learn that the diapausing cocoons were put into cold storage in Germany and then were brought out of cold storage and warmed to 75 degrees F. I believe I was told the moths would emerge in twenty-three days at that constant temperature. Hence the project workers could have emergent moths all winter long simply by staggering the times that the moths were taken out of storage. I suspect that the cocoons were also exposed to extra hours of artificial light.

I have also read of hybrid experiments where cocoons of two closely related species, Saturnia pyri and Saturnia pavonia, were taken out of cold storage at the same time in the spring or where the larger pyri were taken out a few days to a week earlier than the smaller pavonia. The cocoons were slit so that the breeders could monitor the development of the pupae. If it appeared that pupae of one species were developing more rapidly and were going to produce moths before the other species, the rapid developers were cooled and the slower developers were warmed to synchronize emergence times to allow for greater probabilities for hybrid pairings. Obviously temperature has a great influence on the development rate of the pupae.

In nature, I have no doubt that pupae of larvae whose overwintering cocoons are on the ground, buried under fallen leaves in shade of a large tree or building, are going to eclose as moths considerably later (maybe one to three weeks later) than larvae which may have spun up at the same time but whose pupae are in cocoons getting full sun via a southern exposure in a natural heat trap.

Almost every winter in late January to early February I receive emails from people who have found a polyphemus caterpillars crawling on the ground in the fall. They bring the larvae indoors and ask me what needs to be done. I indicate, "The caterpillar is probably going to spin a cocoon in a day or so. Put it in a gallon glass jar with a couple of leaves so you and children can watch this amazing process."

A few days later they email back: "You were right! The caterpillar has spun its cocoon, now what??"

I ask them where they are located and explain that in southerly locales the moth will probably emerge in fourteento eighteen days, inmore northerly locales the insect is going to overwinter in the cocoon/pupal stage in which case I recommend cold storage in a sandwich sized ziploc tub in the refrigerator.

That usually isn't going to work in most households so outdoor or unheated shed storage is recommended. More often than not the fascination with the dull cocoon wanes and instead of going into the fridge, outdoors or into the shed or garage, the cocoon ends up in a box or tray on a shelf in the kitchen.

Almost always the moths emerge in late January early February whether spinup was in September, October or November.

I believe that diapause is broken in such cases by the increased hours of daylight that begin to occur in the northern hemisphere after December 22, the shortest day of the year. Pupae, Antheraea polyphemus pupae in particular, are known to orientate themselves inside their cocoons so that the light sensitive membrane is always oriented toward the primary light source (usually the sun). When light starts filtering into the house in the morning while people are still snuggled in bed under their covers, new development inside the cocoon is triggered by the increased light.

Several years ago, I received from reliable sources, reports that on rare occasions Hyalophora cecropia moths emerge from cocoons, trying to produce a second brood without overwintering. All of the Hyalophora species are well known for being univoltine (single-brooded) whether from Florida or Manitoba.

In the fall (late October) of 2005 I sent island reared Halophora cecropia and Hyalophora columbia cocoons to a photographer who wanted the moths exclusively for photography.

Rather than placing the cocoons in cold storage, he gave them extra warmth, increased hours of artificial light and periodic misting. The moths began eclosing in December. See the images by Darrell Gulin in the 2006 Photography section and in the Hyalophora columbia article in the Bill's Articles section.

Finally, in response to a request for a timeline for larval development, the best I can say is it is going to fluctuate considerably, based on external conditions, primarily temperature. I suspect humidity, food (plant species and moisture and nutritional content), and hours of light and lepidoptera species and time of year are all going to have an impact on rate of development as well.

Many species that come from areas where there are regular sustained hot dry periods seem to be stimulated in their development by the onset of the rainy season. Chris Conlan advised me of this natural "trigger" many years ago. Some pupae, especially the African earth pupators, have been known to remain dormant for many years until someone gives them a good soaking. Nature is a wonderment!

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