Do all scorpions glow under UV light?
As far I can find, the answer is yes for all species of scorpion. There is a chemical compound in a scorpion's exoskeleton called coumarin that fluoresces under UV light. One theory is that this compound, typically found only in plants, is thought to have evolved to protect the scorpion from harmful levels of sunlight long ago.
I've given UV lights to friends going to Iraq and Afghanistan, where there are over five different species of scorpions, and they've found them to be effective in checking tents, outhouses, etc. I can personally verify that scorpions in California, Nevada, Arizona, and Utah definitely light up with a greenish glow :Wow1:
One bit of caution however -- some research indicates that very young scorpions whose new cuticle has not hardened, and those that have very recently moulted, do not fluoresce as much because of lower levels of coumarin in their new exoskeleton.