Antheraea polyphemus (Polyphemus moth)
History:
This is the only Tan North American Saturniidae with a wingspread of up to 6 inches. One of the most distinguishing characteristics of this species are the large eyespots found on the lower hind wings. The IO moth (Automeris io) also has these spots but they are not as colorful nor as interesting as this species. Polyphemus have extensive color variations from very light tan individuals to rusty reds. Some literature indicates that populations have adapted to produce color gradients that fit their environment the best, however I tend to disagree. It has been my observation that larva reared from local populations yield a wide range of color types. The first time I ever saw this species was when I was 22. It was during my time doing an internship up north near Traverse city Michigan. I lived for the summer in a cabin on Bellaire lake. The lake was very pristine and was surrounded by lush forests of mixed hardwoods and contained lots of birch. I decided one evening to set out a light against a sheet to try and see what might come to the lights. 5 male Polyphemus moths flew into the lights and it was a real thrill to see these large moths in person. Since my first encounter I have raised thousands. Even though they are not the brightest or most interesting, they can obtain large sizes near to that of cecropia. This species is wide ranging as far west as California and south to Florida. This species is bivoltine in most of its northern range and multivoltine in its most western and southern ranges with adults on the wing nearly every moth of the year. In Arizona Antheraea oculea a separate species look nearly identical to Polyphemus except that they have a darker sooty overcast on the wings. Polyphemus appear to favor areas composed of mature and semi mature hardwood forests. They are frequently encountered in urban areas and appear to be non effected by development.
Reproduction:
Adult moths lack functional mouthparts or digestive system and therefore they live only for about two weeks. This strategy seems odd as many other species of moths and butterflies feed throughout the period they are adults, but allow me to break down the evolutionary advantages that allow them to do this. The female moth emerges from its cocoon with fully developed ova which allows it to be ready to receive sperm from a male and begin depositing eggs the same night that it hatches. Male moths emerge with large feathery antennae that allow them to detect female pheromones up to a mile away. Males cover long distances flying in a zigzag pattern until pheromone particles have been detected. Females begin “calling” around 10:00 p.m. and continue till dawn. By releasing such effecting means of detection, females do not waste energy flying about seeking mates and reserve all their energy for seeking out host plants appropriate for their larva. Saturniidae regardless of species are by no means ever abundant in the environment. The ability of the males to detect females of the same species from long distances allow them to maintain populations under low density. Female moths frequently will deposit eggs onto the same host plant that they developed on to reduce their weight to allow them to fly away.
Eggs:
large females are capable of laying up to three hundred eggs, but the average is two hundred. Host plant specificity allows the developing larva to more efficiently convert the consumed biomass into fat reserves and tissue. This influences the size of the adult and the possible number of ova that females can carry. Stunted females can carry up to as few as thirty – fifty eggs. Eggs are deposited on the undersides of host leaves in loose groups of three – eight. The eggs can hatch in as little as nine days, or as long as 14 days depending on temperature. They are round in shape and dark on the top and cream around the rim. They resemble a chocolate frosted donut. Fertile eggs that are about to hatch darken slightly. Polyphmus are polyphagous, but depending on their range are highly specialized on a specific host species. Polyphemus in northern ranges of Michigan are found exclusively on river birch (Betula nigra), and White birch (Betula papyrifera). Larval offspring from these populations will refuse acceptance of known food plants used by populations further south. This speaks to genetic aspects that allow certain populations to adapt on a particular host species developing that into a preferred host when nothing else occurs in that area. In general, polyphemus prefer and do best on oaks. Some other host plants I have observed larva feeding on are: Black cherry, willow, and Norway maple.
Larva:
Larva of this species emerge a yellowish green with brown striping. They will consume all or part of the egg shell and soon after will begin to consume the leaves they find themselves upon. Larva of all saturniidae have 5 instars and polyphemus are solitary through all instars. Larva in their second instar are bright green with small red clubs running along either side of their back. The third instar larva are bright green with angled yellow markings along the sides. The fourth and fifth instar are bright translucent yellow-green. They have yellow mid-segmental lines that run from the sub-dorsal scoli to the spiracles along segments 2 to 7. The scoli are silver to gold depending on the angle of the light reflecting off of it. Fifth instars have a yellow band that extends around the dorsal and lateral areas directly behind the head capsule.
Cocoon:
The cocoon is comprised of a single- layer and is thicker and more elliptical that the cocoon of Actias luna. The color is very light tan. Larva usually incorporate a leaf into the construction, however do not always spin silk past the base of the leaf petiole. Due to the variability of construction, some cocoons fall to the ground while others remain hanging on the host plant. Cocoons that do not fall to the ground are easy to spot in the winter.
Pupa:
The pupa of this species obtect with prominent ridges along the upper one-third abdominal segments. Pupa can be sexed with males have a wider more exaggerated antennae line that connect together and completely hide the outline of the legs. Female pupa has an elongated notch just below the last thoracic segment but above the cremaster. Polyphemus pupa wiggle rapidly when disturbed.
Eclose:
Polyphemus in Michigan usually begin emerging in early to mid June. The adult escapes the anterior end of the pupal case by softening and breaking down the silken fibers with an enzyme called coonase. The moths then tear their way from the cocoon with chitinous spurs on the thorax near the bases of the front wings while moving around the cocoon in a circular pattern. Eclosion typically occurs in the afternoon with males emerging a few days before females from the same brood. The moths will climb and hang elevated to expand and dry their wings. Freshly emerged captive raised moths when disturbed will expel a brownish liquid called meconium. This is comprised of breakdown waste of the old larval tissues. As nocturnal Saturniidae they wait till nightfall to take flight. Females reserve flight until they have been mated. It’s a general rule of thumb that if you capture a female at lights that she most likely has been mated and therefore eggs produced should be fertile.
Mortality factors:
Saturniidae larva are large and for most species defenseless. Birds readily seek out both the larva and adult moths. Moths drawn to night lights sit dazzled by the source where they are then picked off buildings once dawn emerges. Bats normally feed on small insects but will not pass up a large moth, leaving only wings as evidence. There are many parasitic fly and wasp species that utilize the larva as a host. Luna and all North American Lepidoptera have taken heavy tolls due to the release of the tachinid fly used in attempt to control gypsy moth populations. Larva can experience high mortality rates due to fungal, bacterial, and viral infection. The larva in nature have no real capacity to combat high density issues and have adapted to leave gregarious habits by the 3rd instar. Pupa are consumed in the winter by hungry squirrels, mice, and woodpeckers who can easily rip through the silk. Polyphemus when disturbed during the day fall to the ground and flop about the ground exposing the eyes on both the upper and hind wings. This strategy is intended to frighten off birds/predators and allow the moth to escape. It has been my general observation however that local birds around my home quickly learn that they are quite edible and ignore this erratic behavior. I’m assuming that normally in the wild birds happen upon these so infrequently that it most likely is an effective means to avoid predation.
Rearing notes:
Polyphemus are easy to rear in outdoor sleeves as well as indoors. They need good ventilation and fresh food at all times. Avoid crowded rearing conditions as this will impact larval development and generally produce small adults. Larva sleeved on the south side of trees develop faster from the heat as compared to ones in more shade. Larva develop into summer non diapause pupa if the day length is greater that 12 hours during the third instar. Non diapause cocoons hatch in about 30 days from when they spin up. I have observed two broods in Michigan so do not assume that all the cocoons will overwinter and set them up to allow any adults that may hatch to hang and dry normally. If after a month and a half nothing hatched assume they will all overwinter and plan on chilling them in the fridge for the duration of the winter till three weeks when you want them to eclose.