Palamnaersus Scorpion from New Mexico

The thin outer layer of the Palamnaersus scorpion's exoskeleton contains a protein that fluoresces a delicate green. The reason for this fluorescence is disputed and a number of theories circulate. Some suggest that the fluorescing molecules provide a sensor for ultraviolet light, signalling to the scorpion dangerous levels of ultraviolet radiation, thus protecting the creature form burning in the sun. This would have served as an evolutional advantage millions of years ago when the composition of the earth's atmosphere was unlike it is today and ultraviolet light from the sun was not efficiently filtered. For the scorpion therefore, an ability to judged the levels of harmful radiation form the sun at differing point in the day was the difference between life and death.