This object, seemingly made out of natural materials, is about 3 inches tall and adhered to a small tree. Credit: Aislinn Sarnacki | BDN | Aislinn Sarnacki | BDN

After viewing photographs of a mysterious object found in the woods of Hampden, several Maine scientists have arrived at the same conclusion: it’s the cocoon of a giant moth.

More specifically, they believe it to be the cocoon of a cecropia moth (Latin name: Hyalophora cecropia), which is the largest moth in North America. With a wingspan of up to 7 inches, the cecropia moth is a silk moth with a reddish body and wings that display an intricate pattern of black, brown, white, red and tan.

“There’s not huge numbers of them, but they’re relatively widespread throughout the continent,” said Charlene Donahue, an entomologist who recently retired from the Maine Forest Service. “They tend to fly in June and July, and late at night, so you don’t often see them.”

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Hampden resident Tony Valcourt was hiking with his dog on April 6, when he found the cocoon attached to the bark of a young tree or shrub. Located about a foot above the ground, the cocoon measured just over 3 inches in diameter and appeared to be spun out of tan or golden silk, with bits of dried grass dispersed evenly over the surface.

“Polyphemus is the only other saturniid [moth] to make a cocoon this large and it usually attaches only at the end,” Donahue said. “The grass is a red herring. Cecropia sometimes incorporate leaves, twigs or grass into their cocoons but not always.”

At the time, Valcourt wasn’t sure what the object was, so he snapped a few photos and posted them on Facebook. Since then, hundreds of people have guessed at the sac’s identity — and what might be inside. Many thought that it might be a bird’s nest of some sort, while others suspected it was a man-made object, perhaps camouflage for a trail camera.

The BDN looked into the mystery by following Valcourt to the cocoon on April 8, to take photos and record information, such as its size, then consulted with wildlife biologists throughout Maine.

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“I narrowed it down to a cocoon of either a polyphemus moth or cecropia moth, both giant silk moths in the family Saturniidae,” Phillip deMaynadier, wildlife biologist for the Maine Department of Inland Fisheries and Wildlife, told the BDN. “And then, when I queried two expert entomologist colleagues, Charlene Donahue and John Calhoun, both independently confirmed it as the latter — cecropia moth.”

Kevin Tracewski, Clay Kirby and Jerry Longcore — all three Maine residents with backgrounds in entomology — also believe it’s a cecropia moth cocoon.

“I encountered one of these, without all the dead grass on it about 13 years ago,” Longcore said. “I was curious so I kept visiting it until the moth inside emerged.”

In addition, an entomologist studying a University of Massachusetts Boston, Teá Kesting-Handly, contacted the BDN to state that she believes it’s a cecropia moth. She also thinks it’s possible, though less likely, that it’s a Columbia Silkmoth, which is in the same family.

“[I] have reared this species many many times,” Kesting-Handly said of the cecropia moth. “I am extremely confident in this ID, and have IDed it now several times on Facebook groups.”

Like all moths, the cecropia moth changes a great deal throughout its life cycle. It emerges from an egg as a spiky, black caterpillar, which feeds on the leaves of a wide variety of trees and shrubs, including maple, birch, willow, elm and apple.

As a caterpillar, it changes color from black to yellow to bright green as it grows to be plump and about 4 inches long. All over its body are projections or “tubercles” tipped with black spines. By the time the caterpillar turns green, these tubercles have turned bright yellow, sky blue and red, making the caterpillar appear quite exotic.

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“Both the caterpillar and the adult life phases of the cecropia moth are quite striking,” deMaynadier said.

Yet somehow, they’re easy to overlook, Donahue said.

“It’s amazing how they blend in with the foliage,” she said. “A number of years ago, a guy brought one in [to me while working] and it was on a twig from a blueberry bush — a skinny little twig with a few leaves on it — and this giant caterpillar was on it, and when you looked at the branch, you didn’t see that caterpillar. It was like, how can that possibly be?”

To transform into a moth, its adult form, the cecropia caterpillar spins a large, multi-layered cocoon out of silk — usually on a woody branch. It then spends the entire winter in the cocoon, morphing into an adult with magnificent wings that emerges in early summer.

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“It’s unusual to see an adult cecropia moth in the wild,” deMaynadier said, “partly because they are uncommon — though not rare — and mostly because the probability of encounter is low given their behavior. Like many other giant silk moths, cecropias are nocturnal. Also, they don’t have developed mouth parts or even a digestive system, so they aren’t attracted to flowers or other food sources as are most butterflies and moths. As a result, they only live a couple weeks with the primary purpose of finding a mate and propagating. To this end the male’s enlarged radar-like antennae are important, helping it navigate a ‘pheromone trail’ up to a mile away to find receptive females.”

Like many other moths, the cecropia moth is attracted to light. For this reason, Donahue saw these giant moths on a regular basis while running a monitoring program for the Maine Forest Service that involved the use of light traps to attract moths and other insects.

“They’d be caught in traps and brought in, so we’d get them from all over the state,” Donahue said. “Usually it’d just be a few of them each year — not a huge number. Part of that is because of their behavior. They are attracted to light but they don’t come right to the light. They will flutter at the edge of the light cone and often fall to the ground like they’re having a fit. It’s an odd behavior, but then sometimes you’ll see them the next day resting nearby.”

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In response to the first BDN story about the cocoon — then just a “mysterious object” in the woods — many BDN readers commented on the story online or reached out via email to offer their best guesses as to what it could be. The guesses included a harvest mouse nest, burl, miniature woodland coconut, portal to an alternate universe, hummingbird nest, spider nest, Body Snatchers pod, praying mantis nest, ant or wasp nest, gnome nest and Chupacabra egg case. A number of people did state that it was a giant moth cocoon, and some even specified that it was a cecropia moth. Well done.

After the story ran, Anita Lopez of Bingham sent the BDN a photo of a strikingly similar object that she recently found while exploring ATV trails near her home. It, too, measured about 3 inches in diameter. Based on the photos, Donahue confirmed that it’s likely another cecropia moth cocoon, though the moth incorporated white pine needles instead of grass into the structure.

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These intricate structures, captivating people on the internet, are great examples of how amazing nature can be.

“It’s pretty cool to see the life cycle and learn about something you don’t see everyday,” Valcourt said. “I’m glad that a lot of people will know what it is if they come across one now.”

Have you found something interesting in the Maine wilderness? Aislinn Sarnacki can be reached at asarnacki@bangordailynews.com or 207-990-8287. Follow her on Twitter: @1minhikegirl, and Instagram: @actoutdoors.

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Aislinn Sarnacki

Aislinn is a Bangor Daily News reporter for the Outdoors pages, focusing on outdoor recreation and Maine wildlife. Visit her main blog at actoutwithaislinn.bangordailynews.com.