Q. Why do scorpions glow under black light? What might the evolutionary advantage be?

A. Certain molecules in one layer of the cuticle, the tough but somewhat flexible part of a scorpion’s exoskeleton, absorb the longer wavelengths of ultraviolet light and emit it in different wavelengths that are visible at night as a blue-green glow.

Several theories have been advanced about the usefulness of this fluorescence, perhaps in finding prey or in courtship, without experimental corroboration.

A study led by Carl T. Kloock in 2011 found that the fluorescence seemed to help scorpions detect and avoid ultraviolet light.

In 2012, further research published in the journal Animal Behavior by Douglas Gaffin of the University of Oklahoma tested how scorpions reacted to both ultraviolet and blue-green light with their eyes blocked and unblocked. They showed a stronger avoidance reaction to ultraviolet light than expected from the sensitivity of their eyes, and even stronger avoidance when they were exposed to green light with their eyes blocked.