Eli5: spiders and UV light


What does it mean when a spider can reflect light in the UV part of the electromagnetic spectrum? Can all spiders do it and what does that even mean in correlation to humans? Does that help the spider in any way?

In: 10

When you see something it’s because visible light is being reflected off of an object.

There are other wavelengths of light that aren’t visible to us, like infrared and ultraviolet.

Spiders are made of something that is able to reflect ultraviolet radiation.

It doesn’t have anything to do with humans.

It could help them keep birds away because bright flashy colors usually means that the animal is poisonous. (Birds can see ultraviolet light)