Tiny 'mirror-ball' spiders hide in plain sight with crystal patches that work 'like a disco ball'

A tiny spider with a body that flashes like a disco ball gave social media users one more reason to marvel at the natural world.

A post on Reddit drew attention to so-called mirror-ball spiders, explaining how these glittering arachnids manage to hide in plain sight.

What happened?

Just beneath the surface of a Thwaitesia spider's abdomen are crystalline cells associated with guanine-based reflective patches.

Those crystals spread out when the spider is relaxed and pull inward when it is disturbed.

"Spiders of the genus Thwaitesia are often described as mirror-ball spiders, because their bodies are lined with reflective panels that make them look like tiny disco-balls," the original poster wrote. "They're also known as dewdrop spiders or sequined spiders."

Across the Southern Hemisphere, more than 22 species have been identified in South America, Southeast Asia, Africa, Australia, India, Sri Lanka, China, Singapore, and Madagascar. 

These spiders are typically only about 2 to 4 millimeters long and are not considered dangerous to humans.

Why does it matter?

Scientists think the spiders' shine may function as camouflage in rainforest environments, with the panels resembling beads of dew or raindrops.

The same reflective patterning could also throw light in ways that make the spiders hard for predators to detect.

"This spider's decorative patterning may seem like a dead giveaway to predators," according to Science Friday, which the poster cited. "But for those looking to feast on the arachnid, a species in the genus Thwaitesia, the hunt might result in confusion and failure."

Arachnologist Robert Whyte described it this way: "Like a disco ball with lots of different mirrors [that] scatter light and make it difficult for predators to see it."

What are people saying?

Commenters were fascinated by the biology behind the sparkle.

"OK, wait. The fact that this is basically the same stuff that gives fish scales their shine is blowing my mind. Nature really recycled the same sparkly ingredient for both spiders and fish, and we're just here wearing glitter we bought at the craft store," one person wrote.

Others kept their reactions simple.

"That is very cool! Thank you for sharing," one person replied.

Not everyone was entirely won over, however. "Thank you for letting me know where I'll not be visiting! I'm terrified of spiders. I can't even fully appreciate this little guy!" one spider skeptic said.

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