Peacock Spider

Tiny. Most peacock spiders are between about 2.5 and 6 millimetres long — smaller than a grain of rice, and small enough that the astonishing colour and detail of the males is invisible to the naked eye and only became widely known through macro photography and video. The largest species reach around 7 millimetres. Their small size is part of why so many species went undescribed until recently — you have to be looking closely, in the right patch of habitat, at the right time of year, to find them.

To court a female without being eaten. Female peacock spiders are larger, and an unreceptive or unimpressed female will often attack and cannibalise a courting male. The male's only route to mating is to convince her, from a safe distance, that he is a high-quality mate of the right species. He does this with a multi-part display — he raises his brightly patterned abdomen like a fan, waves one or both ornamented legs in species-specific patterns, and sways from side to side, all while drumming vibrational signals into the ground that she picks up through her legs. He constantly adjusts — moving to stay in her field of view, intensifying the display if her attention drifts. If she is satisfied she signals receptivity; if not, he needs to retreat fast.

Mostly not from pigments. The brilliant blues, purples, and greens are structural colours — the male's scales and cuticle contain microscopic three-dimensional architectures — layered films, diffraction gratings, and tiny lens- and brush-shaped scales — that interfere with light so that only certain wavelengths are reflected back intensely. The reds and yellows do come from pigments. Some species also have patches of "super black" cuticle, covered in microscopic bumps that trap almost all light (reflecting under 0.5%), placed right next to the colourful areas so the colours look even more saturated by contrast, much as a jeweller sets a gem against black velvet.

They are completely harmless to humans. They are jumping spiders, they have venom for subduing insect prey, but they are far too small to break human skin meaningfully and they are not aggressive — a peacock spider is more likely to turn and look at you with curiosity than to flee. Some enthusiasts do keep them, and a few species have been bred in captivity, but they are short-lived (adults survive only a few months), need live insect food and carefully controlled humidity, and many species have never been kept successfully. Given that several species have extremely restricted wild ranges, responsible keepers avoid taking them from vulnerable populations.