For nearly three decades, the words “mini Stonehenge” have made people smirk as they remembered the classic scene from the movie This is Spinal Tap, when the band’s live concert set of Stonehenge is mistakenly built to be 18 inches tall instead of 18 feet.

However, since last summer people in the entomological community have been more likely to think about a tiny Stonehenge replica that was found in Peru and has come to be known as Spiderhenge or Silkhenge.

Spinal Tap’s Stonehenge (top) and Silkhenge or Spiderhenge (bottom).

In September 2013, National Geographic described it as a tiny “mysterious picket fence,” and WIRED Magazine called it a “weird web-tower thing.”

A graduate student from Georgia Tech named Troy Alexander found the first one in June near the Tambopata Research Center in southeastern Peru, and he found three more after that on tree trunks. Scientists and journalists were baffled, and no one could figure out what it was for or who had made it.

“I’ve talked to researchers worldwide and haven’t found an answer,” Alexander said at the time.

A close look revealed that it was made of silk-like threads, which led people to believe that it must have been made by an insect or related arthropod. Then a few months later in December, the theory was confirmed.

Naturalist Phil Torres, along with University of Florida entomologists Lary Reeves and Geena Hill and photographer Jeff Cremer, went into the rainforest and observed the structures. After six days they finally saw two tiny spiderlings emerge from the base, and when they saw a third one hatch the following day, they were convinced that a spider was building these things.

This is one of the tiny spiders that emerged from Silkhenge.

The fence-like structure around the perimeter may serve as a defensive wall to protect the egg at the center, but no one really knows for sure. Likewise, no one is really sure what species of spider these things are.

Read more at:

– We Went to the Amazon to Find Out What Makes These Weird Web-Tower Things

– We Solved An Amazon Rainforest Mystery

– Mystery in the Amazon solved: Miniature towers surrounded by ‘picket fences’ on trees are found to be spiders egg-nests