Changing Planet

What Created This Mysterious “Picket Fence” in the Amazon?

It’s probably the only picket fence in the Amazon, but scientists have no idea what made it or what its purpose might be.

Georgia Tech doctoral student Troy Alexander stumbled upon these two-centimeter-long white structures growing on trees in Peru on June 7. (Also see “What’s This Mysterious Circle on the Seafloor?“)

The picket fence of the Amazon. Photograph courtesy Troy S. Alexander, Tambopata Research Center

Since then, the intricate handiwork has baffled scientists. Although most agree it was likely built by an insect, no one can identify the species that built it, or what the fence might be protecting.

“I thought anything this distinctive would have been discovered already,” Alexander said.

“I’ve talked to researchers worldwide and haven’t found an answer, so I don’t feel crazy saying that I’ve found a new species, or at the very least, a new behavior,” he said.

“What Is That?”

Alexander made the discovery when he was volunteering at the Tambopata Research Center as part of the Tambopata Macaw Project. He noticed something unusual on one of the blue tarps the group was working under for shade. (Read more about a new species of decoy spider that was discovered at Tambopata.)

“I looked up and thought, ‘What is that?'” Alexander said. “At the time, I thought a Urodid moth had started building a cocoon and then just got distracted and didn’t finish or got eaten.”

Troy Alexander picture
Alexander in the Peruvian Amazon. Photograph courtesy Troy S. Alexander, Tambopata Research Center

Intrigued, Alexander snapped a few photos to show an entomologist back at the center. But the expert had never seen anything like it. Neither had anyone on Reddit’s What’s This Bug group, where Alexander also posted the photo.

Soon after, he saw several more of these structures, which consist of a tall, white conical post in the middle, surrounded by what can only be described as a small, circular white picket fence.

Having spotted several, Alexander knew that this wasn’t just the efforts of a distracted moth. He posted these new photos on Reddit and got a few suggestions, but nothing conclusive. Alexander’s leading hypothesis—one proposed by a Reddit reader—is that the structure was spun and built by a spider instead of a standard web. (Also see “Photos: World’s Biggest, Strongest Spider Webs Found.”)

Instead of spinnerets, or silk-spinning organs, some spiders have what’s called a cribellum, which, instead of spinning silk fibers, pushes the molecules through a fine mesh.

“Looking more closely at the photos, I thought, yeah, that does make sense. It does look like the silk was just pushed through a mesh,” Alexander said.

Unveiling the Mystery Builder

Alexander, who’s working on his Ph.D. in natural drug discovery, said he intends to stick with his chosen field, even with the glut of attention he has received from his Amazonian discovery.

mysterious structure picture
The mystery object is less than an inch long. Photograph courtesy Troy S. Alexander, Tambopata Research Center

He added he’d like to go back to Tambopata, although he doesn’t have plans to return in the immediate future. Luckily though, an entomologist will be traveling to the research center this winter to try to identify what’s building the forest fences.

When asked what he would name his find if it proved to be a new species, Alexander said he would need to learn some Latin so he could incorporate the word for “fence” in the name.

What would you like to name this unusual fence-builder? Share your thoughts below!

Follow Carrie Arnold on Twitter and Google+.

Carrie is a freelance science writer living in Virginia. When she's not writing about cool critters, she's spending time outside, drinking coffee, or knitting. You can visit her website at
  • william wesley

    I would assume an insect egg is in the central stalk or was at its tip and hatched, the fence keeps out ants and probably has chemicals to repel them as well. how about the “guard tower” insect?

  • Janet Cobbs

    Guess: Spider built the “fence” to keep harmful bugs from entering the coccoon and eating contents. Just a different kind of spider web. Am anxious for your findings.

  • CM

    To me it likes like an egg pouch surrounded by spider webbing. Did anyone bother asking the natives, I’m sure they’ve come across it and probably know quite a lot about it?

  • Eve

    Interesting. ..i would name it “wizard of webs”

  • mtwzzyzx

    It looks like a spider produced it, and the little thing suspended between the central column element and the fence in the first photo could be an insect caught and bundled, or just some jungle detritus that floated in. Perhaps it resembles a flower in some way, and so attracts insects looking for flowers.

  • Terry Knouff

    What do you mean “What Created This Mysterious “Picket Fence” in the Amazon?”, it just “appeared” through a random serious of atomic interactions. Like Einstein, or chicken soup. Right ?

  • Mr Gary Tucknott

    Built by a small spider … a tent-like cage to protect its eggs.
    The egg sack is in the middle with a tent-post protruding up to support guy ropes to the tops of the cage side-walls.
    The spider webbing forms an intricate cage to keep small insect raiders from plundering the spider’s nest.
    I would call it a Cage Spider.

  • Ima Ryma

    We sent some scouts to check it out,
    A planet – third rock from a sun.
    Found some weird creatures all about.
    Each called itself a human one.
    The scouts went where few humans were,
    And installed the homing hardware.
    We have locked in signals secure,
    And concluded we can thrive there.
    A few humans have found the tech,
    Call it a picket fence made by
    Some new bug – oh well, what the heck!
    Humans will find out too late why.

    The scout signals are right on tune.
    Aliens and we’re coming soon.

  • Moreach

    Has it been established what is inside the cone? I reminds me very much of spider egg structures in composition. I could see the “fence” being a way to retain the baby spiders an extra day or two once they hatch… or protect them from… Interesting amazing structure.

  • Mark

    Since the structures have what seems like 30 or 31 “fence posts” this is clearly evidence of a complex spider created lunar calendar system.

  • Tom Kerr. (Not important-your pictures are!)

    Unbelievably awesome. It looks like some sort of intricate egg fence compound and support/sensor wires to protect the developing eggs from ants and such. Wonder what sort of clever unknown beastie made it?

  • email

    Somebody put the following comment on MSN under this same photo. Can NG officially confirm or dismiss it?
    “Are you kidding me that’s a nest of a Peruvian waltzing spider, same picture was taken by explorer Len Snorsen and was displayed in NG mag in 1933.Look it up.”

  • Inam Ul-Haq

    Just wait and see what hatches.

  • David Farrant

    Clearly a spidery Stonehenge. Probably would be a good idea to check its celestial alignment.

  • Gabbie Barnard

    I have questions. Was a spider actually seen by the anomaly? It looks like a fungus to me not a web. I can’t see a spider. Fungi are known for growing in circles like the fairy circles we sometimes find. It looks like a sundial on the side of a tree, or a miniature stone henge.

  • Peter

    The whole egg sac protection seems straightforward, logical but also simple. I’m sure there are more photos but the first one seems to have something on it. If it were a spider it would gave to be very small to do the finest work. In anycase anything that spins a web of any sort are never far from it.

  • kevin erickson

    that is clearly the head of a pikman lol
    jokes aside that is pretty darn cool

  • cortnnie

    I would call it a fairy

  • Michelle

    The little fence could be to catch tiny bugs or grow a form of moss/fungus for the babies to eat when they are hatched.

  • Tammy kimbrell

    How about prison spider , if its a spider. Prison whatever it may be because all of it is bound together behind a fence and to the fence . Or prisoner whatever it is.. Sounds appropriate to me…

  • Anne G Chipman

    Contego serica means Silken Defense in Latin I believe…would seem appropriate!

  • Ericson Orola

    Saruman Spider:)

  • Margit Roberts

    I would name it, “The Unicorn in Captivity”. As soon as I saw the photo it reminded me of the famous tapestry.

  • Tone-Lise Magnussen

    Could it be a fungal, that a spider has added some web onto?

  • denise lanzisera

    if you enlarge the photo at about 8 o’clock you can see the front of a small robust furry
    brown spider :-/

  • Betel Geuse

    Charlotte’s Web!!!

  • Matt Bear-Fowler

    I think it’s possibly a fungus of some kind. Something like a new kind of mushroom.

  • Aaron Horrell

    Have they asked the local indigenous? They’ve likely seen this before, unless it’s a new thing, which seems unlikely.


    Since no one has seen an insect build the fence, could it be a type of plant that evolved from another plant. While the article is fascinating, I wonder of all of the structures are uniform in size and shape. Spiders tend to leave unique signatures in their webs. How many are there and are they all built into moss on trees? So many variables are left to ponder, with minimal information. I agree it is an amazing discovery and look forward to reading more about it.

  • Lis Stedman

    I would call it the Picket Fence Spider, if indeed it is a spider, which would seem likely. Amazing structure…

  • Lisa Drouin

    -Picket Aracnid
    -Deceiver Spider
    -Miner Spider (fences in anything he thinks is ‘mine’)

  • Anastasia

    Is that a spider I see in the right hand side of the structure? If not a spider egg sac… Then why not suggest a fungus? Or some type of parasitic species ? It for Whatever reason doesn’t really strike me as odd… But on the other hand, I’d want certain identification as well. Maybe a native to the area?

  • Bridgett Hendricks

    AWESOME! Would call it “PicketHenge”

  • tyrell coker

    if I had a chance to name a discovery such as this one and found out that indeed it was a spider that created it I would have to call it “Luna Araneus” meaning moon spider in Latin

  • Ididwhatlastnight

    There is a new type of paintball that contains corn starch and water. There was a match nearby. Game on!

  • Christian Romero

    Amazing! It remember’s me an image of a sperm trying to enter into an ovule. I will called it “fecundatio” spider (fecundatio, Latin = fecundation).

  • Gordon Stogre

    Just when “MAN” thought he knew everything about everything… We know so little of what God has created. That’s why we’ll need eternity to learn about the universe! 70 or 80 years just won’t cut it!

  • kevin grant

    I think that the post in the middle is scented to attract insects. They will try and get into the post in the middle, but will get trapped trying to climb over it. The spider will check back at his traps to see if hes caught anything.

  • kevin grant

    Or theres eggs in the centre. The fence around it catches bugs for when the spiders hatch. They will have a meal as soon as they hatch.

  • Trip Affleck

    hah! nicely done Ima Ryma! [and i see what you did there!]

  • tanya

    The outter circle(fence) is a protective webbing. The center is most likely an egg sack. The outter web grabs the unwanted guest before reaching the eggs. Amazing.. Makes you wonder if there brains have grown stronger. Interesting science experiment for sure

  • Karl E

    How about aedificator sepem. Latin for “fence builder”

  • Trip Affleck

    such a gossamer fence couldn’t possibly afford any protection from a predator. however, there do seem to be threads attached between the fence and the center structure; and if you click on the top image, you see a thread at the very tip of the center structure leading off to the left, off camera. could it be a “baited hook” for a creature that might respond to the vibrations created by the attached threads during an incursion into the interior?

  • Jen

    sepes. For example, Phoneutria sepes.

  • Amy Bloom

    Looks like Saruman’s tower (called Orthanc) from Lord of the Rings…a tall white tower, surrounded by an empty circular field. They should call it the Orthanc spider

  • J Barrett

    Tree Henge

  • sadia

    I would have studied molecular characteristics i.e what it is made up of?which protein?…would help in knowing either these threads are similar to spider web….
    I would have tried to find DNA sequence homology.
    how strong this structure is?upon touch does it feel like? sticky like spider web?

  • Thiago André

    Looks like a fence…ok… but isn´t it a little fragile to be a fence??And other thing…the write colour gets attentions inside the dark green of a forest/ Woudn´t be camouflage??maybe a pioson kind of fungus that is known by the litlte guys to be dangerous so they don´t get close to it?The chemical ideia William sad is another cool possibility!!!Of course I am just guessing people, not saying anything for sure……

  • mario beaudet

    i dont no my spell is correct but because i speak french normaly . i like you check the tree on side road this place
    454 cumberland—–new westminster
    british columbia—–canada

  • jules

    I’d say it’s the Guantanamomoth

  • Edwardos

    Call it the Picket Bug. That’s a good name for something that creates fences. If it’s a beetle call it ‘picket beetle’.

  • Mark Travis

    My 12 year old said name it ( Hershey Corral )

  • Liz

    What a great find…..I would name it “The Castle spider”

  • Jun CJ Nofies

    I’m sure a species of spider created this fence.. whether it’s made as an insect trap or for protection. How about asking the people living near them? I’m sure they encounter that fence hundred times and saw who’s creating it.

    I’ll simply call it “Fence Spider”

    ..and the scientific name should be like, ‘Saepemque Aráneamis’ …well, let the scientists name it.

  • John Webber

    I’ve seen something like this years ago bit i can’t remember exactly where. It may have been where i grew up in Northern California or it could have been during my travels in the military. When this story first appeared the other day i recognized that structure immediately.

  • Sabarika

    The threadlike structure and makeup draws me to thinking it is insect-related, much like spider silk, but may not be a spider. The structure itself reminds me of a sundial though, I don’;t have any real suggestions other than that.

  • Andreen Anderson

    The 3-D Crop Circle Spinner Spider!

  • ruhaima mousa

    I think it’s a spider web trying to protect something looks like egg. Any way, am anxious to know the answer

  • Carl Pearson

    it looks like a structured construction. the center post is set firmly and the outer post erected, then smaller threads of silk linking all together. Looks like a fence we would put up to keep people out of our yards or territory. looks like the fence is to protect whats in the center…. i go with the spiderhenge or arachnasafe

  • Carlo Sironi

    Da inesperto totale io credo che l’autore di ciò sia un
    ragno, che ha deposto le uova nella sacca centrale di seta e
    che ha eretto quella sorta di palizzata a protezione di alcuni
    Carlo Sironi

  • Karen

    As a world traveler and teacher of art, science,WorldGeography&GEO Bee proctor I love the worldwide feedback and creativity for this fascinating find!

  • anil jagtap

    I would call it The Aliens Work.

  • Михаил Токарев

    I think that as a trap that the construction is not necessary – flying insects easily going to get out of it, and crawling into it will not penetrate. It could equally be a spider structure or some sort of caterpillar, which pupated in the central cocoon. Or maybe it’s a fungus.

  • Jeanne Chen

    I think the thing in the middle is a pocket for eggs. then the small fence is for protection of the babies

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