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Dave, if you found a hairy featureless creature inside, that is the second or inner cocoon. The real creature to become a moth is inside that and does have features of the possible moth, ie. you can see the antennae and the small wings which have to be pumped up with fluids. It would be better not to cut into that cocoon, as it is protection from germs as well as enemies that would like to eat it. If you keep it in the house now it will come out soon, and there will be no leaves for it to lay its eggs on or another mate out there even. Keep it protected outside in a cool, non sunny spot in a largish container into which you can place a stick. It needs to be able to crawl up on it and hang upside down for about an hour undisturbed while it pumps up its wings and then dries them out to a rigid form so they can fly properly. So it needs a lot of free space for the large wings to be. As you say it is a tan colour, it is most likely a Polyphemus Moth. It definitely is not one of the Sphrinidae, the sphinx moths, as they do not have the ability to spin cocoons; very little silk production except for buttons when they change an instar stage as a caterpillar. Instead they protect themselves by buring themselves in loose soil in the fall, so one rarely sees one unless you happen to dig one up in your garden unharmed by the shovel or spading fork, or capture a large, mature hornworm caterpillar in the late summer/fall and put it into a jar of loose, slightly moistened soil. Within minutes, if not seconds, usually they will bury right down in it. Unfortunately they do not change from a caterpillar to a pupa next to the glass, as they seek the dark. But if you cannot stand the suspense, after a few days you can dump the soil out of the jar and find the pupa. Whether you can put it back in the jar with the soil successfully, I do not know. It may need that air space which it made getting into the soil, even though it fills in a bit for its own air supply and moisture. When trying to raise such creatures through people often do not give them enough humidity, so they dry out before they can emerge. Alone in nature they face plenty of rain and snow and ice. It actually helps to run water over them once a week (non chlorinated, please!!) or keep the soil a bit moist if that is where they are pupating. As to emerging in nature, it depends on the weather. If it is unusually cool they will be a little slower than "normal", and if the days and nights are warmer than usual, then they will be a little earlier. They time themselves pretty accurately as to when the leaves will be ready for their young ones, which take about 12 -14 days to hatch from the eggs. Polyphemus usually prefer any of the birches. The adult does not have mouth parts, so lives only 10- 12 days on stored energy picked up as a caterpillar, just long enough to pass on its DNA and begin another cycle. Come to think of it I should ask you where you found the cocoon! Was it attached to branches as in a small bush/tree or was it loose on the ground. If the latter was the location, then it could be a luna moth. They are tannish in colour, too, but spin on the ground using leaves in which to wrap themselves. Good luck with it, and please let us know if something interesting occurs in about mid June to late June depending on the weather, of course!! JET PS. If the cocoon was warmish, then the sun must have been on it, or the warmth of your hand warmed it up quickly. Insects are cold blooded and do not radiate warmth but have to absorb it from the sun or surrounding which is why we see very few insects in the winter time, except some specialized ones like snow fleas. If you hold your cocoon in your hand for a minute or two or even less, it may wiggle in response to the warmth as a Mexican jumping bean does. Then you will know it is still alive. Often, unfortuantely -but it is part of nature - the big caterpillars are often parasitized by the Ichumid Wasps. The caterpillar lives long enough to spin its cocoon, but the eggs of the wasp will bury into the pupa then and its young will use it for food, so instead of a pretty moth which you hope for, you may end of raising a jar full of wasps! The cocoon will feel quite light, but it takes practice to know if it is a viable or not. If a moth has not emerged by mid July, cut into the inner cocoon and perhaps you can determine what happened to it, but there are a variety of possibilities of course!
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