The Polyphemus Moth
(Antheraea polyphemus, Cramer, 1776)


Male Polyphemus moth by Dan MacKinnon

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TAXONOMY:

Superfamily: Bombycoidea, Latreille, 1802
Family: Saturniidae, Boisduval, [1837] 1834
Subfamily: Saturniinae, Boisduval, [1837] 1834
Tribe: Saturniini, Boisduval, [1837] 1834
Genus: Antheraea, Hubner, 1819

DISTRIBUTION:

The polyphemus moth (Antherea polyphemus) is North America's most widely distributed large silkmoth (wingspan up to 6 inches). Native populations exist in all U.S. states and Canadian provinces except Alaska, Arizona, Hawaii, Nevada, and Newfoundland.

These moths are quite common here on Prince Edward Island, Canada, despite being listed as absent from this province in "The Wild Silk Moths of North America".

FLIGHT TIMES:

In Canada and U.S. border states Antheraea polyphemus is univoltine (single brooded). Most adult moths fly from late May to July.

In New Jersey, the Ohio River Valley, and westward the species is bivoltine (double brooded). Winter diapause stock (pupae that have remained in cocoons over the winter) usually emerges in April or May and second brood adults emerge in July or August.

In Texas and Florida adults fly in every month except January.

On January 25, 2003, I received a report of a pair of polyphemus in Florida. Adult moths were seen in the same area in late November.

Vernon Brou reports that there are five peak flights in Lousiana at 47 day intervals from mid- March through September.

On January 30, 2003, I received a report of an outdoor polyphemus emergence from Baton Rouge, Louisiana on January 29. I suspect there is at least a partial sixth brood in La., or changes in weather patterns are creating changes in flight seasons.

Fourth instar caterpillars experiencing sixteen hours of daylight/day progress directly from larvae to pupae to adult moths while those fourth instar larvae that experience only twelve hours of daylight/day enter a pupal diapause that will take them through the winter months. The diapause will be broken by increasing hours of daylight and warmer temperatures. Hence springtime weather conditions will determine whether there are one, two, or three broods in a given year.
Males tend to emerge two to three days before females.

Here on P.E.I., Canada, cocoons removed from cold storage (refrigerator crisper) in spring produce adults in twenty-one to twenty-eight days when kept at room temperature (24-25 C or 75-77 F).


ECLOSION:

The adults tend to eclose or emerge from their cocoons in the early afternoon.


Photo by Dan MacKinnon with inserts from Kurt Himmelbauer.

The adult secretes a chemical called cocoonase to break down or soften the sericin that binds the silk strands of the cocoon. Hornlike projections at the base of the forewing are then used to tear at the silk while strong legs continuously heave the moth forward until it can escape from its valveless cocoon.


This event sometimes creates a racket in an indoor emergence cage, but the process usually only lasts a few minutes. The moth must now climb up the side of its emergence cage or up a stem or tree trunk so that its wings can hang freely while fluid is pumped into the numerous veins in the wings. After about twenty minutes this "inflation" process is complete and the wings soon stiffen in preparation for flight. Males tend to fly shortly after dusk. Females seldom fly until after mating.


SCENTING AND MATING:

Females begin releasing their pheromone, a 90:10 mixture of chemical attractant consisting of 6 cis-11-hexadecadienyl acetate and trans-6, cis-11-hexacadienal aldehyde, at approximately 10:00 pm and continue scenting until mating or around 1:00 am.

Unmated females scent again just before dawn. The scent gland protrudes from the posterior end of the abdomen.


Photo courtesy of David Wilbur.


The same gland is used to expel and affix sticky eggs to the undersides of leaves.
Flying males zigzag into the wind to locate the female scent plume with their highly developed antennae: 60,000 sensilla and 150,000 receptors.

The female moth pictured on the left has much smaller antennae than the male to the right. The color differences are not typical of gender, but merely of variations within the species.


Photo courtesy of M. Whitmore.


Photo courtesy of Dan MacKinnon


Males can only fly in temperatures above 7 C or 45 F and have been known to fly many miles in a single evening. Colder temperatures prevent the males from thermoregulating body temperatues by vibrating the wings. This species mates readily in captivity, even in small cages (one cubic foot) according to some texts, but I have not found this to be so on P.E.I. Almost all of my matings occur when wild males fly in to my caged, scenting females. I seldom get pairings with males in the cages.

Once paired, the couple tend to stay paired until the following evening. A single mating will fertilize all of the 200-350 eggs. Males may mate again, but ova may not be viable. Sperm in the female receptacles triggers ovulation responses, but even unmated females begin laying eggs after two or three evenings.

OVA, LARVAE, COCOONS, AND PUPAE:

Relatively large, off-white ova with a brown band around the horizontal circumference are laid singly or in groups of three to five on host plant leaves.

Incubation lasts ten to fourteen days. Emerging caterpillars chew through one side of the the egg. Photos by David Wilbur.

The larvae eat most of their eggshells and spend six to eight weeks passing through five instars as green caterpillars.

The large brown heads, typical of polyphemus larvae, are evident even in the first instar.

Larvae stop feeding and become quiescent for a day or two before shedding skins to make way for new growth. They should not be disturbed at this time.


Relatively few larvae fasten their cocoons to the tree branch with a peduncle, although this practice seems more common in southern latitudes. In the north more larvae spin cocoons in a leaf wrap that will fall to the ground, or larvae descend the tree to spin up in surrounding grasses. The larval gut is cleared via a loose, runny stool just prior to the spinning of a compact oval cocoon. The larvae secrete a substance that hardens the cocoon.

Pupae can be sexed by removing them from cocoons. The outline of the antennae is clearly visible on the pupal shell.

I usually don't remove pupae from cocoons. If I want to sex them or check for disease or parasitization, I will usually just use a sharp pair of scissors to cut a slit across one of the longer axis.

IT IS INTERESTING THAT PUPAE ORIENT THEMSELVES SO THAT THE DORSAL SURFACE IS ALWAYS SKYWARD. IF THE COCOON IS ROTATED, THE PUPAE WILL WIGGLE SO AS TO REORIENTATE THEMSELVES TOWARD THE LIGHT.


The silkmoths of the eastern U.S. and Canada have very distinctive cocoons.

Click on caterpillar to see a large image and access a listing of preferred and alternate foodplants.

Click on notes to access seasonal notes on A. Polyphemus.

Google lists at least one site for each of the following Saturniidae genera: Actias, Adelocephala, Adeloneivaia, Adelowalkeria, Adetomeris, Agapema, Aglia, Anisota, Antheraea, Antherina, Antistathmoptera, Archaeoattacus, Argema, Arsenura, Athletes (need species), Attacus, Aurivillius, Automerella, Automerina, Automeris, Bunaea, Bunaeopsis, Caio (need species), Caligula (need species), Callosamia, Catocephala, Cinabra, Cirina (need species), Citheronia, Citioica, Coloradia, Copaxa, Copiopteryx, Coscinocera, Cricula, Decachorda, Dirphia, Dirphiopsis, Dryocampa, Dysdaemonia, Eacles, Eochroa, Epiphora, Eriogyna, Eubergia, Eudyaria, Eupackardia, Eustera, Gamelia, Gonimbrasia, Goodia, Graellsia, Gynanisa, Heliconisa, Hemileuca, Heniocha, Holocerina, Homoeopteryx, Hyalophora, Hylesia, Hyperchiria, Imbrasia, Ithomisa, Lemaireia, Leucanella, Lobobunaea, Loepa, Lonomia, ludia, Melanocera, Micragone, Molippa, Neoris, Nudaurelia, Oiticella, Opodiphthera, Ormiscodes, Orthogonioptilium, Othorene, Paradirphia, Perisomena, Periphoba, Polythysana, Procitheronia, Pselaphelia, Pseudaphelia, Pseudantheraea, Pseudautomeris, Pseudimbrasia, Pseudobunaea, Pseudodirphia, Psilopygida, Ptiloscola, Rhescynthis, Rhodinia, Rohaniella, Rothschildia, Salassa (need species: lola), Samia, Saturnia, Schausiella, Syssphinx, Tagoropsis, Titaea, Urota, Usta (need species:terpsichore), Vegetia.

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