Polyphemus moth…those “eyespots”

Going to the market, my spouse and children stumbled upon a giant fuzzy winged creature. They returned home with all sorts of questions. The puzzle was whether it had been a moth or a butterfly, and what kind. So, with all our guesses and guide books exhausted, little Eva and I returned to the site with our hypotheses. We walked two blocks…my 3 year old lead the way…and remembered exactly which tree it was on. “There it is!”, she exclaimed with pride and excitement. And, what a treasure indeed…. a gigantic, plump, fuzzy, and colorful female moth.

She remained quite still, with wings pressed back firmly. She appeared to be resting, and maybe her wings were still expanding and drying after a twilight emergence from a silken cocoon (she exhibited a posture similar to Luna moths I’ve observed during emergence, and her wing tips were still a bit moist and wavy). She had very delicate and detailed antennae, and was covered with reddish brown fuzz, the exact same reddish brown visible on the exposed inner bark of the tree behind her. She was certainly a moth, and we could tell she was a “she” by the size of those antennae….they were rather small…much smaller than the receptive fans the males carry around.
Antheraea polyphemus Her belly was huge. It really looked like it was going to burst. We concluded that this very evening would be the evening she laid her eggs in the tree above. She might place a few here and there, on the underside of the leaves. Her offspring will voraciously consume leaves, and chop them off at their petioles after eating each one, a behavior that apparently helps prevent predators from detecting the caterpillars’ presence. Her tree of choice was a Northern Red Oak, one of many potential host plants for this moth’s young, .

We watched, and pondered her very short and focused adult life….living not more than a week in moth form, and not feeding (no mouth parts!). We pondered how the caterpillars would consume nearly 80,000 times their body weight, an essential step in preparing for the pointed task of reproduction as an adult moth.
With some patience, and some encouragement, the wings began to open and spread flat against the tree. Her attempt to spook us (predators) made us say “Wow!”.
Those spots were striking. “Owl eye mimicry” has been the frequently used phrase. Well recently, studies demonstrated different reasons for the eyespot patterns…
Conspicuousness, not mimicry.
It appears that these patterns are there to distract, startle, and misdirect the attacking predator. In fact, if you touch the back of the moth it will either expose its bright “eyespots” by spreading the wings wide or quickly snap the wings shut on your finger. Both responses are quite startling.
It is enthralling to consider the long evolutionary history of attack, evasion, and mutation that might result in such distinct patterns and behaviors.
I wonder… when, in the distant geo-ecological past, was this genetic variety selected for? I also wonder how many thousands of beautiful varieties we are missing today because they were selected against!
For an overview of recent findings on “eyespot” mimicry, read this fascinating article:

http://www.sciencedaily.com/releases/2008/02/080221090250.htm

5 thoughts on “Polyphemus moth…those “eyespots”

  1. Tree hugging says:

    I used to raise these moths, along with Luna moths. We moth started with one female adult moth that we mail ordered as a cocoon. If you put a female in a cage then it'll attract any wild males for miles around.

    After mating, they tend to lay their eggs only a few at a time in different trees. In captivity though they have no choice but to lay them all at once.

    Probably the coolest critter I've ever seeen in the city though was a Hercules beetle. I had no idea that any native insect could get so HUGE or be so beautiful. I'd grow those too but grubs freak me out.

  2. Anonymous says:

    Based on a question from Ruth D.:
    "If the female is ready to lay eggs, how did those eggs get fertilized?".
    From what I've read, most females are fertilized on the first night, immediately after emerging…as with lunas, emergence probably happens between 7-10pm.
    I think it's very likely that the moth in the image is full of eggs. The other possiblity is that it is infested with something (wasp predator?..larvae?). I did notice a small black dot on the side of its abdomen, but assumed it was mark from an attacking bird. One thing that I may have been wrong about was that it was still drying its wings. It is actually more likely that the wings were fully expanded and ready for flight the night before…say by 11-12 pm.
    Maybe "Tree hugging" can shed some light on this, as he has reared them before.

  3. Tree hugging says:

    Yeah, males find them pretty quickly, and unlike males females don't fly much. From the moment they emerge they are full of eggs. Initially they just wait in one spot for males to come to them. Reportedly males can "smell" them for huge distances (and in my experience this seems to be true). After mating, they go on their last and only flight putting just a few eggs on each tree (The cynthia moth eats ailanthus, but this tendancy to lay only a few eggs means that it was never a good control). After that flight, they run out of energy and die.

    Your theory about the hole sounds right. It's probably a predatory wasp. Even in captivity I'd still get those from time to time (they're sneaky).

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