[scottdupoy]

Agreed. Scorpions also glow under UV light and scientists don't seem to have come up with definite theory explaining why this may be. Maybe these are just random occurrences of proteins that glow under UV, but have other properties beneficial to the animal in question.

[todd8]

My theory about these scorpions is that it is protective coloration (aposematism) that warns potential predators, in this case likely birds and reptiles that are capable of seeing uv colors due to tetrachromacy. See [1] and [2].

[1] https://en.m.wikipedia.org/wiki/Aposematism

[2] https://en.m.wikipedia.org/wiki/Tetrachromacy

[indecisive_user]

Tetrachromacy does not necessarily imply the ability to see UV colors. There's a non trivial number of women that are tetrachromats[1] and they can just see more shades in the same color spectrum as most people.

[1] http://www.bbc.com/future/story/20140905-the-women-with-supe...

[planteen]

Keep in mind that puffins and scorpions are fluorescing. So the excitation is UV light, but the emission is in the visible spectrum. So tetrachromacity doesn't necessarily come into play. The ability to resolve the emission colors through the contrast of the day is the relevant capability for observers.

Once you learn to recognize florescence, you notice it on some objects with optical brighteners in daylight (e.g., blaze orange products, certain laundry detergents on clothing).