They look like delicate jeweled Halloween decorations, but these spooky spiders are very much alive! Mirror Spiders, or twin-peaked Thwaitesia are found in Australia and feature reflective patches on their bodies.
The scales look like solid pieces of mirror glued to the spider’s back, but they can actually change size depending on how threatened the spider feels. The reflective scales are composed of reflective guanine, which these and other spiders use to give themselves color. The deposits of guanine are often accumulated into large blobs, which often resemble a glittery mosaic. They are tiny, with an average body length of around 3 mm (0.12 in).
Robert Whyte studies Australian spiders and explained “The mirror spider is so common around creek lines, especially in Brisbane. I can describe to a six-year-old — its size and how it sparkles — and within five minutes they’ll go out looking for it.”
“It’s a particularly good camouflage in the tropical areas where it rains more because you have rain drops which also sparkle in the sun, and so the spider goes relatively unnoticed.”