The spots on male peacock spider body reflect less than half a percent of light, which makes them darker than normal black color and causes an optical illusion that they almost glow. This is how male peacock spiders woo females.
The spiders’ sophisticated mating games include dances during which a male spider swings to attract the attention of its chosen female with its spectacular colors. Red and yellow hues on the spider’s abdomen are produced by special pigments. You can also see blue and purple hues caused by the interaction of light with the spider’s tiny hairs.
But what is most amazing about them are bright black patches attributable to both the pigmentation and tiny bumps that reflect the light so that the observer does not see it. As a result, an illusion of small glowing spots is created making male spiders irresistible to female ones.