What's That Bug? does not endorse extermination

cocoon my daughter brought home
Location: Bloomington, Minnesota (found in winter)
February 10, 2012 8:50 am
My 8 year old daughter loves bugs, especially moths and butterflies. She recently brought this cocoon home and put it in a jar. After probably almost two months this bug came out. I have googled for hours and been unsuccessful in identifying the species, and since she wants to keep it I want to make sure we are feeding it correctly, so it would be great if you could tell me what it is.
After hatching it began laying eggs and spinning silk. It is very large and bulbous, especially in the bottom of the body. The wings do not seem to help it fly successfully. The wings aren’t flat the way most seem to be, they are formed a very odd way. And it has hair inbetween them. It’s probably 2” long, with a 2.5” wingspan. The body is probably 3/8” in diameter.
Signature: Thank you very much, from a lil bug lover’s mother

Deformed Polyphemus Moth

Dear lil bug lover’s mother,
Your story is one of the sweetest we have received in such a long time.  Don’t get us wrong, we love researching the names of insects, and exotic species are often very difficult for us, but we would much rather a philosophical question like yours.  Alas, we have bad news for the lil bug lover, though is is not really that sad and we hope you can use this as a learning experience for her.  This is a female Polyphemus Moth, a native North American species that can be found coast to coast if the habitat is conducive to its needs.  Your observation that the wings are unusual is correct, however, this is an abnormality that prevented this moth from being able to fly.  Normally the wings expand as the veins fill with body fluids.  If the moth is able to use its fluids properly, the wings harden and expand.  The moth takes its name from
the Cyclops Polyphemus  of the Odyssey by Homer, the ancient Greek chronicler.  One can only speculate why the wings did not expand.  Perhaps a genetic mutation.  Perhaps trauma endured during the collection process.  If the cocoon is held too tightly, it might damage the dormant pupa within.  Perhaps the confined conditions of the bottle where it emerged was not a habitat conducive to its needs.  Though this flightless female did not mate, she probably needed to download some eggs in her bloated state.  In the wild, she would have taken flight and released pheromones that the male could sense with his considerably larger and feathered antennae.  Others of her species would have emerged at the same time because conditions like temperature and humidity triggered metamorphosis.  She would fly and release pheromones   The male and female would actually engage in intercourse and he would fertilize the eggs in her womb.  She would then fly and lay eggs on the correct deciduous trees, of which there are many (see BugGuide).
Here is the really interesting part.  Adult Polyphemus Moths do not eat, so nothing is going to appeal to her.  The mouth parts, known as the proboscis, are absent, so she cannot consume nourishment like other adults or imago of her order, Lepidoptera.  Adult Giant Silkmoths in the family Saturniidae do not feed and they only live a few days, long enough to mate and lay eggs.  Many adult Giant Silkmoths are eaten by birds and other predators.  Evolution has caused many species to develop eye spots or ocelli that will scare a predator into thinking it is being attacked by a much larger creature with a huge face, perhaps even a human.

To Be Continued…….

UPDATE:  February 13, 2012
Hello again lil bug lover’s mother,

We wanted to try to provide you with a bit more information if your daughter continues to be interested in collecting cocoons so that she can observe the metamorphosis process.  The scientific term for the emergence of an organism from a dormant state, be it egg or pupa, is eclosion.  Caution your daughter to handle the cocoon very carefully.  The ideal habitat is one that is large enough to house the adult comfortably and will provide ample space for the wing expansion.  Jars are not ideal.  Cardboard boxes at least the size of a shoe box fitted with a screen cover are a much better solution.  You also want to avoid premature eclosion.  This Polyphemus Moth was not provided with an opportunity to find a mate, or to have a mate find her, because she emerged during the depths of winter in Minnesota.  If you have a protected and unheated porch or garage that is closer in temperature to the outdoors, but safe from elements and predators, that is ideal.  Then eclosion can occur when the conditions are suited for the rest of the species.  Once the moths emerge, they can safely expand their wings and be released.  Butterflies and moths do not make the best pets since they need to fly and most captive environments do not provide enough space.  Caterpillars can be raised quite successfully however.  On a positive note, if the failure for the wings to expand had been genetic and not a result of trauma, this moth would surely have perished much sooner in the wild, however, the truncated wings would not have prevented mating, and if a male Polyphemus had ecloded in the vicinity, they could have mated.  Good luck with future endeavors.

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What's That Bug? does not endorse extermination
Location: Minnesota

2 Responses to Female Polyphemus Moth: Hatches with deformed wings and lays unfertilized eggs!!!

  1. Dave says:

    Hi Daniel,

    It’s great to read your description. Sometimes I think that most of those who write about insects either demonize them or render them through scientific discourse. Neither of those approaches can help us appreciate what’s around us.

    Best,

    Dave

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