UNUSUAL ASPECTS OF THE LIFE CYCLE OF SATURNIID MOTHS
Reprinted with Permission from Young Entomologists Society VOL 3 (4) FALL 1986
Gary L. Lovell
3818 Watson Street
Toledo, OH 43612 USA
During the past 15 years I have collected, raised and observed several species of Saturniids (giant silk moths). Many people are already familiar with their life cycle, so I would like to focus on some interesting aspects I have encountered while observing the short-lived adult stage. One of the most intriguing aspects of behavior involves the assembly of males.
In North America there are many Saturniinae, but the species I have concentrated on are Hyalophora cecropia, Antherea polyphemus, Callosamia promethea, and Actias luna. The first two are very common in the Toledo (Ohio) area and the cocoons are easily obtained. The latter two are less common. The cocoon of A. luna is found on the ground and it is virtually impossible to find. In order to study the Luna I found it necessary to purchase cocoons from a biological supply house, then mate the adults and rear the larvae.
If you are going to assemble moths, the first thing you must have is a freshly emerged female of the desired species. Place the moth in a cage with adequate ventilation. Sometimes I place the female directly in the cage; other times I let it emerge from the cocoon in the cage so I don’t have to disturb it.
The time period during which a female moth releases pheromone (or “scent”) varies with the species. The four species I mentioned run the spectrum from 7:00 p.m. to 6:00 a.m. EDT (Eastern Daylight Savings Time). However, the time the female releases her pheromone and the time the first males begin to arrive are not necessarily the same. The Promethea releases pheromone between 7:00 p.m. and dark; the Luna about 11:00 -12:00 p.m.; the Polyphemus between 2:00 and 4:00 a.m.; and, the Cecropia between 4:00 a.m. and dawn.
I have gotten up many nights at the proper time to observe the results. I would almost always be surprised. Sometimes I would have more specimens than I could handle, and other times there would be none. The number of males attracted depends on such things as weather and population distribution. One thing I’ve noticed about the Cecropia female is that she may not release her pheromone on the first night if she is small in size.
If undisturbed, the females are usually content to sit quietly until after mating. Sometimes if I’m short of females I let her attract males, but I keep her isolated so that she is not mated. This way I can extend my experiments over several days or until the next female emerges.
My first surprise observation was in 1970 when a friend’s Cecropia female attracted 10 males in a single night. We only expected one or two! But as long as you protect the female from potential mates she will continue to release pheromone until the end of the species pheromone period. In the meantime, every male within range of the pheromone will probably find his way to the female. Of course, under natural conditions that probably won’t happen because the first male to arrive will mate with the female.
Originally we thought that ten males was phenomenal. But on several other occasions that year we attracted up to 25 males. On June 30, 1974, with 4 females producing pheromone, we broke our previous record. From my notes: “Males started coming before 4:00 a.m. and continued until 5:30 a.m. We surpassed the record before 5:00 a.m., and reached 45 by 5:31 a.m. (EDT).” In 1979 I was able to record new records of 47 and then 48 males (in one night). The most incredible night occurred in 1980, on June 26: “6:00 a.m. (EDT) –111 male Cecropia moths attracted to two females. Caught as many as I could, but saw at least 2 others I could not catch. An unbelievable number for me to grasp. Starting about 4:40 until 5:45 a.m..” Neither my friends nor I have ever seen a night like that one since!
One of the experiments I do with these males is to mark them with paints and set them free after mating with the female, or the next evening. I mark them with different colors so that I can differentiate between different release days. The results have been variable and are somewhat dependent on the number caught and released, but this past year I got 3 out of 5 (60%) to return. Our usual return rate is 10%. For example, one day in 1974 I attracted 20 males and only 2 were marked. All the rest were new.
Through the use of different colored markings I have discovered that some male moths come back night after night. And, several have skipped a night and then come back the next night. One even came back after a four day absence. Some have come from different locations.
An example of a large number of returned males with different markings came on the day after-the 111 specimens were attracted. I released 105 of them marked with red paint. On the 27th of June (1980) a friend and I caught only 91 males. From my notes “Had a big turnout of marked ones. •most marked ones were red from June 26 evening… Five were red and yellow ones from earlier release… total of 35 were marked.”
From these different groups one can see a cross section of large, small, new or battered individuals. A sample of the composition comes from the 111 specimens of June 26 (1980): “Besides large and small, there was another badly tattered one… Several had holes pecked in their rear eye spot as if birds had attempted to eat them. Most were perfect, and a few had small chips off wings.”
Another thing I’ve noticed about male Cecropia moths is that the hair on the last abdominal segment near the reproductive organs gets worn off during mating. If this is a reliable indicator of mating activity, then I can say that both mated and unmated males will come to waiting females. With the Lunas I had last summer, two males mated twice with different females. However, half of all eggs from the four females did not hatch, indicating, perhaps, that the males spent themselves on the first female.
Polyphemus moths are very sensitive to disturbances, and the pheromone seems not to spread great distances with the result being that we rarely get more than one or two males, if at all. At Mud Lake in the Irish Hills of Michigan, we once got 9 males in a single night. Promethea is easy to handle, but their usual habitat is even further away so the most we have gotten is 2 males.
I’ve had no experience attracting Luna moths. Last year I purchased some cocoons and the adults easily mated in a cage after nightfall. This generally does not work for the Polyphemus and Cecropia because their pheromone period is much later and the males want to fly as soon as it is dark. Hence they could be tired and their wings could be torn to shreds by the time the female is ready.
I have kept a daily record of the emergence of our captive cocoons since 1971. I recorded the sex and number of each species that emerged daily. Some years we collected more than others, with a range of 72 (1983) to 8 (1984) and an average of 40 per year. The earliest emergence date in the Toledo (Ohio) area was May 16. The season lasts about 6 to 8 weeks and ends around the second week of July. Antheraea polyphemus adults emerge from about June 1 to July 25th. Our local Promethea (one brood I believe) emerge in early to mid July. The only twelve Luna cocoons I had (from a supply house in the southern United States) all hatched during the third week of May. The second brood of six hatched during the last week of July.
In a typical year, the peak of the season (which I determine by the day most of my cocoons emerge, and which I assume is proportionate to the “wild” cocoons) is close to the same date each year. According to my notes, the Cecropia peak is during the third week of June: June 19, 24 and 28 coming up several times each. The highest number that emerged in one day is 9, with an average of 4 to 5. In 1975 and 1976 my records show an especially early emergence for the Cecropia, probably due to a large number of captive-raised caterpillars. All of the captive-raised cocoons hatched earlier for reasons not yet clear to me.
After the moth mating season is over, I attempt to raise the larvae for experiments in the following year.
As you can see from this discussion, the Saturniids demonstrate a wide variety of behavior and activity patterns which makes them all the more interesting. If anyone has had similar (or different) experience with these moths, I hope they will publish the information in Y.E.S. and/or write to me at glovell1@sbcglobal.net .
*** A video clip of the 111 males that came to two females on June 26 1980— https://yjoutu.be/u-2jZKsksA . Shown on the TV but one couldn’t see the video because my head was in the way. Now in its entirety.
Unusual Perspectives 