Fluourescent Scorpions: Love and Danger in the Dark

Scorpions  at night in the desert, viewed with a blacklight.

One of the coolest night collecting tricks is to take a black light out to look for scorpions.  In the desert (and even in the woods where I live) these cryptic stinging critters emerge at night to hunt, and although they are well camouflaged a simple black light reveals them in glowing color.  There’s a lot of debate about why scorpions fluoresce under ultraviolet light but it may be a further mechanism to help them avoid light (which makes them vulnerable to predators and dehydration).

Scorpions that are not hungry reduce activity on brightly moonlit nights.  Being able to detect and head towards dark areas can also help an organism with relatively poor eyesight to quickly identify refuges such as rocks and bushes (Camp & Gaffin 1999).  Gaffin et al. found that, when blindfolded, scorpions could use their entire exoskeleton as a sensor to detect UV light (2011).  I am now enjoying picturing scorpions in tiny blindfolds.

Two scorpions fighting (or courting?) in the desert at night.

I encountered this particular pair of scorpions in the desert in Arizona.  At first I thought they might be engaged in courtship behavior, but later I thought they might just be fighting (possibly both?).   Yes, I know the pictures look a bit violent with the wrestling and the stinging, but scorpion courtship is, well, probably only fun for scorpions.  I can’t find the excellent clip from Life in the Undergrowth, but there are some lovely videos of scorpion mating dances on Youtube.  For many species, stinging is involved.  Also elaborate dancing, and chewing on each other’s faces (“kissing”).  The courtship is completed when the male manuevers the female backwards onto a spiky spermatophore he has placed on a flat surface.

Two scorpions: fighting or making out?

 

In a Pinch — the Scorpion’s Chelicerae

The chelicerae of a scorpion are visible as it devours a cricket.

8legs2many today!  I found this little guy hunting near a lightsheet at the Welder Wildlife Refuge.   As a general rule of thumb smaller pincers mean a more powerful sting, so I took care handling this little guy.  Above, you can see him chowing down on a feeder cricket I gave him.

Like spiders, scorpions are arachnids, with eight pairs of walking legs.  Their large front claws are not true legs, but actually modified pedipalps, appendages on the prosoma used by chelicerate arthropods for handling food.  While snapping pictures and shooting video clips of this guy I also got a chance to get a close up look at another cool appendage– the chelicerae.  These are two sharp pincer-like mouthparts used to grab the food and tear off small pieces.  These are pulled into the preoral cavity, where food is digested externally prior to being sucked down in liquid form.  Chelicerae are unique to a subgroup of arthropods called the Chelicerata–which includes arachnids, horseshoe crabs, and a weird little group called the sea spiders.  In spiders the chelicerae bear the fangs (these were the metallic green mouthparts we saw on the bold jumping spider a few posts ago).

Scorpions actually make pretty interesting pets, needing only a warm dark environment with some kind of refuge.  Scorpions (and other arachnids) lack the cuticular layer of wax which protects insects from dessication. * It is important to maintain high humidity to prevent them from drying out, particularly for tropical species.  They are nocturnal, and so most active at night, which is the best time to feed them.  Because they are adapted to living in darkness, they are sensitive to UV light, which can harm them with prolonged exposure.  They also fluoresce vividly under a blacklight, which can be a fun way to hunt for them at night, although, again, longterm exposure should be avoided.

*Edit:  See comments below.  Thanks, Dave!