MadSci Network: Zoology

Re: Why do emporer scorpions glow blue under a black light?

Date: Mon Sep 20 11:42:25 1999
Posted By: Rob Campbell, Oceanography, University of British Columbia
Area of science: Zoology
ID: 937621083.Zo

Hi Eric-

Searching under "emporer scorpion" at Yahoo yields a whole bunch of sites, that you can check out.

One of them mentions that this is probably an adaptation to lure in prey. These scorpions reflect ultraviolet (UV) light, which is what makes them glow under black light. Scorpions are predators, and hunt by capturing their prey with their pincers and stabbing with their barbed stinger- while they will take mice or small birds that are unlucky to get too close, they generally eat insects. It turns out that many plants emit ultraviolet light signals that draws in pollinators, which are often insects (e.g. bees); by reflecting UV light, the scorpion may be, in a sense, "pretending" to be a flower. Also, many insects are what we call phototactic, which basically means that they are attracted to light- by emitting a strong UV signal, the emperor scorpion could be taking advantage of this phototactic behaviour to attract prey.

So, you can see that a UV reflecting scorpion has an advantage over a non-UV reflecting scorpion, because it could attract more prey. Because a UV reflecting scorpion might be able to grow bigger and be less likely to be eaten by a predator, or last longer when food became scarce, their survival would probably be greater than a non-UV reflecting scorpion who gets less to eat. Under natural selection, one could expect an advantageous trait like UV reflection to become more predominant, until eventually it became the only trait found (i.e. as the non-reflectors got eaten or died off in hard times)- this is how it would evolve.

Rob Campbell, MAD Scientist.

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