In the jungles of Peru and the Philippines, some of the smallest spiders on Earth are building monsters. Each web they spin hides a puppet—crafted from dead insects, leaves, and silk—that looks uncannily like a much larger spider. When predators move in, it’s showtime.

The new research, published Nov. 6 in Ecology and Evolution, describes how Cyclosa inca and Cyclosa longicauda create realistic spider replicas inside their webs. Each decoy is several times larger than its maker, with long legs, a segmented body, and the unmistakable shape of a giant arachnid suspended in midair. Some appear abstract, while others could pass for the real thing at a glance.

“They don’t just decorate their webs,” said George Olah, a conservation geneticist at the Australian National University who led the s

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