[CaptMoldman (OP)]

I'm speaking strictly of "biofluorescence" here, not bioluminescence.

[chris]

I'm speaking strictly of "biofluorescence" here, not bioluminescence.

Perhaps you could explain the distinction between these two terms, and to what sorts of animals each applies?

[RD]

I'm speaking strictly of "biofluorescence" here ...

e.g. fluorescent scorpions ...
 

The luminescence doesn't persist after the UV light is removed , so it's not functioning as a light-source to enable the scorpion to hunt at night.

If it has a benefit, ( it could just be a neutral phenomenon ), I suspect it's a method of re-radiating solar energy, the UV component, to lower the odds of being damaged by the desert sun, cf. sun-screen.

[Colin2B]

The point RD makes is an important one.
We often assume that if an adaption or gene has survived it must have supplied a benefit to the host. But the host might have survived due to other stronger benefits and the particular feature or gene just hitchhiked. Lucky gene.

[CaptMoldman (OP)]

Insightful answers! Thanks so much. It perplexed me how a trait would survive that seemed to be so rarely activated (if at all) but the piggybacking theory makes a lot of sense.