RARE Arizona Bark Scorpion with TWO Metasomas (Tails) and Stingers!

On Sunday evening, August 14, 2016, BJ Stacey (@finatic) and I were black lighting for insects in Madera Canyon, Santa Cruz County, Arizona, at the Carrie Nation Trailhead, when I decided to do a scorpion check with my handheld black light. I made a short walk along the edge of the parking lot - something I have done there countless times before - and stumbled across an expected species for the area known as the Arizona Bark Scorpion (Centruroides sculpturatus). This species is easily recognized by its frequently reddish coloration and contrasting dark back with a line of pale spots running its length.

I observed it for a minute before I realized that something was "off". By now BJ had arrived to photo it and it was at this moment that I noticed that it must be two individuals mating, which didn't sit very well with me because I hadn't ever seen mating scorpions riding each others' backs. When I quickly realized that there was only one set of legs and chelae, it suddenly dawned on me that I was looking at a single Bark Scorpion with two metasomas and two stingers! (View photos of this individual here: http://www.inaturalist.org/observations/3902604). After exclaiming that I had a two-tailed scorpion I quickly pulled a vial out of my pocket and VERY CAREFULLY collected it. Arizona Bark Scorpion is by far the most venomous scorpion north of Mexico and is well known in its range as causing severe pain following a sting, and can even lead to death in the very young or very old. In Arizona, it is frequently found in peoples' homes where of course most often they are promptly dispatched. In the case of this juvenile individual, it is quite small, so it would likely have some trouble breaking human skin without a very precise and direct contact, if it can at all.

After bringing it home alive and well, and after gaining permission from my wife to maintain such a creature at least for a period of time (!!), I released it into a terrarium I have ready to accept a scorpion for observation. Her thought was the same as mine that something so rare should be observed to document its behavior. We are experienced with scorpions in captivity, having kept multiple scorpions for this purpose in the past, typically releasing them back where they were found at some point. This specimen will likely never be released, largely in part to the fact that typically these don't survive very long in the wild (or in captivity, for that matter) due to molting issues. That said, there are very few examples.

Scorpions with two tails are extremely rarely observed, and one estimate I found online said that it occurs in only one of every 5,000 individuals. It is my first. Others who are far more experienced with scorpions than I, and who have themselves observed many thousands of individuals have told me they have not yet found one.

I have not been able to fully examine this specimen as yet to determine the exact structural characteristics of the double metasoma, but one other feature worth mentioning is that its right lower chelal claw is significantly stunted, rendering that claw unusable for grasping. See below for additional behavioral information pertaining to its chelal use.

I will use this journal entry as an ongoing record of my observations of this individual, so please check back over time for updates. I look forward to your thoughts and comments, and I'll say it now to get it out of the way - It is not for sale or trade (and I have already turned down offers).

FYI @miketroll @sidesplotch @jmaughn @dominic @rjadams55


8/15/16 - Placed in its terrarium of sandy substrate and a hiding place. Walking around acquainting itself with its new home.

8/16/16 - Small insects including a winged termite and beetles placed in its enclosure, but it is not interested. Getting worried that it may not eat. Placed water droplets in the sand, and it quickly went over to it and very obviously laid down in it. Do they absorb water through their bodies? Added a shallow water dish.

8/17/16 - Caught a small moth at my light and dropped it in.

8/18/16 - In the morning I found four moth wings (phew!) and a still-alive termite (now wingless). Removed the termite. Does not like termites, check! (NOTE: All scorpions seem to be somewhat finicky eaters, so trial-and-error is important. No scorpion that I have kept has ever turned down a moth though).

8/20/16 - Caught a greenbottle fly and removed a wing before dropping it in the enclosure. Now well-hydrated and having eaten a couple of days prior, it aggressively ran toward the fly, grabbed it with its one good chela (the other also being used as a prod) and incredibly stung it accurately with BOTH stingers almost simultaneously! It is quite interesting that it would be able to accomplish this considering scorpions have evolved over millions of years to hunt with a single stinger. I will seek to photo/video document this in the near future.

8/20/16 - Metasoma function: I have been observing the individual's use of its metasomas since capture, and can state that they are each fully and seemingly equally functional in every manner. They are sometimes held over the body, sometimes both off to the side, and sometimes one up with the other down. While eating the fly, it crossed them (I will resist the temptation to anthropomorphize!)

8/22/16 - Ate two small moths, but I was not able to witness the kills.

8/23/16 - Consumed an Alfalfa Looper moth that was bulkier than itself (with one forewing removed). This individual has zero issues with kills, despite its one stunted chela.

8/26/16 - Some type of buildup collected in one of its metasomas, so I removed the buildup with forceps and moved the scorpion to a dry habitat in case it is a cause of the buildup.

8/30/16 - Tail buildup has not returned, so hopefully was a one-time event. It is eating voraciously almost daily, including a termite (so scratch the earlier reference to not liking termites).

9/17/16 - I re-configured its enclosure using pulverized coconut husk as the substrate, which it much prefers vs. sand and is more like its normal habitat. I will mist the aquarium glass periodically to maintain appropriate moisture levels.

10/14/16 - I captured a brief video of the scorpion attempting to kill a cricket, though the cricket proved a bit too fast (video link posted just below). I feel this was a half-hearted attempt, as it did not make subsequent attempts on it. This gives a good solid impression of this scorpion's routine of stinging prey with both stingers simultaneously. I'll try again with this same cricket soon, and hopefully capture an actual kill. https://www.flickr.com/photos/71649753@N07/29720781973/in/dateposted-public/

10/26/16 - After 83 days in captivity, it has finally molted (ecdysis)! This photograph was taken approximately two hours after it completed the task, apparently with perfect success. Interestingly, the right lower claw (visible in this photo) which was already malformed at the time of discovery, has lengthened relative to the upper claw. I suspected that it would soon be shedding its exoskeleton after it began to shun any prey twelve days prior.

10/31/16 - Took a cricket for the first time since its pre-molt fast began on October 14. It is still a tiny bit soft, so I monitored it carefully after introducing the cricket to make sure no damage was done. It wasn't particularly proficient with its stingers yet, and it didn't sting it before simply starting to eat its head. It still cannot grasp with its right claw, despite the slight relative lengthening following the ecdyisis, but used it as a prod as it had prior.

4/4/18 - Minor update that this individual is still doing well in captivity. It has not molted since 10/26/16.

Posted on August 21, 2016 01:54 AM by jaykeller jaykeller


Photos / Sounds


Arizona Bark Scorpion (Centruroides sculpturatus)




August 14, 2016


Scorpions with two metasomae (tails) are extremely rare, with one estimate I saw as one in every 5,000 specimens. This specimen is approximately 3cm long head to stinger and is being maintained in captivity to study its behavior.

I found this using a black light flashlight with BJ Stacey (@finatic) at the Carrie Nation Trailhead parking lot at Madera Canyon, Arizona.

Read a detailed account of this specimen's discovery and observation updates at the journal post linked below:


Excellent find Jay! A remarkable creature.

Posted by silversea_starsong almost 8 years ago

This is fascinating, Jay, and a nice job of logging the encounter. I can't help but think that it has been through several molts to get to this size, so wish it luck in the future. It's a backward scorpion - one (good) chela, two metasomas! With that double-dose of venom, be especially careful around the critter.

Posted by stevejones almost 8 years ago

Good points Steve, and thanks James!

Posted by jaykeller almost 8 years ago


Posted by sea-kangaroo almost 8 years ago

Wow that's the coolest thing ever! How lucky are you!!! Thanks for sharing. Can't wait to see what happens in the future. You should do a video and put it on youtube. I know a couple of people who would love to see this critter including me lol. ;-)

Posted by dominic almost 8 years ago

I do hope to get some good video for sure! The way it used both stingers today on the fly simultaneously was amazing.

Posted by jaykeller almost 8 years ago

Oh, wow!

Posted by jmaughn almost 8 years ago

Woooooow. So awesome. :)

Posted by sambiology almost 8 years ago

Thank you for sharing your observation with us and supplying the additional information. I will certainly look for further updates from you.

It certainly is hard to not anthropomorphize! Here I am, wondering what you have named it!

Posted by connlindajo almost 8 years ago

No names! ;-) Can't get to attached to this one. Though I do tend to call it "the barker", but I refer to all of these that way.

Posted by jaykeller almost 8 years ago

That is an incredible find! Thank you for logging it and sharing your observations! I look forward to seeing its progress in the future.

Posted by rjadams55 almost 8 years ago

amazing find, how long is it from mouth to end of stinger, we might be able to get an idea of what instar it is at? do you know its sex?

Posted by miketroll almost 8 years ago

I am not yet sure of the sex, but I more carefully measured it this evening and it is 3cm mouth to stinger, give or take a mm or two. Hard to precisely measure it. Last night it ate an Alfalfa Looper moth bulkier than itself, so it is very aggressive and proficient.

Posted by jaykeller almost 8 years ago

Very cool indeed! It's like finding a left-handed shell coiled gastropod in a species that is normally always right-handed. :)

Posted by susanhewitt almost 8 years ago

Just a quick note that all is well with this critter, and is eating me out of house and home! I hope to have video of it feeding shortly.

Posted by jaykeller over 7 years ago

Thank you for the update. I, for one, eagerly await the video!

Posted by jmaughn over 7 years ago

I agree with @jmaughn! Can't wait for the video either lol.

Posted by dominic over 7 years ago

With over 40 years of collecting and observing, I still have yet to find one! Scorpions can be sexed at an early instar by the shape of the pectines near the base. I didn't see how you were keeping it, but don't forget how mesic it is at the parking lot, definitely not desert. Cool find and excellent notes! Worthy of a publication!

Posted by kjmcwest over 7 years ago

Do try to video ecdysis if you get lucky!

Posted by kjmcwest over 7 years ago

Thanks @kjmcwest! I forgot to update here (as I did in the associated ob) that I completely reconfigured its enclosure back in mid-September with pulverized coconut husk, which retains humidity sufficiently with regular misting without encouraging mold growth. It seems very happy with its conditions, and has clearly fattened and grown, though has not yet molted.

Posted by jaykeller over 7 years ago

Oh, and I have captured a couple of decent videos of it feeding, but haven't quite gotten THE one yet. Still working on it. I'll get it eventually.

Posted by jaykeller over 7 years ago

Cool! I would love to see video of it stinging its prey! Post a photo of its underside, like in a ziploc upside-down.

Posted by kjmcwest over 7 years ago

I captured a brief video of the scorpion attempting to kill a cricket, though the cricket proved a bit too fast (video link posted just below). I feel this was a half-hearted attempt due to being well-fed, as it did not make subsequent attempts on it. This gives a good solid impression of this scorpion's routine of stinging prey with both stingers simultaneously. I'll try again with this same cricket soon, and hopefully capture an actual kill. https://www.flickr.com/photos/71649753@N07/29720781973/in/dateposted-public/

Posted by jaykeller over 7 years ago

Nice video! Thanks!

Posted by susanhewitt over 7 years ago

It has shed its exoskeleton with perfect success! See a photo and notes about the event at the below link or in the above captivity notes: https://www.flickr.com/photos/71649753@N07/30472204372/in/dateposted-public/

Posted by jaykeller over 7 years ago

That's just too cool, Jay! Nice work!

Posted by stevejones over 7 years ago

Thanks Steve! That's a BIG "phew" that it successfully molted!

Posted by jaykeller over 7 years ago

Just a note to mention that all is still well with this specimen. Eating well, and we've settled into a rhythm. I guess they live about 8 years...

Posted by jaykeller over 7 years ago

What an Awesome observation! How much longer until it is fully grown? Have you considered breeding it to see if this trait is genetically heritable?

Posted by naturenate about 7 years ago

Hello Everyone. We're coming up on a year since discovery of this two-tailed Arizona Bark Scorpion, and I wanted to let you know that it is doing quite well in captivity. It feeds extremely well, and takes about anything I give it except for beetles. I have learned a ton about this species over the past year, an has been a very rewarding experience overall.

I also currently maintain a Stahnkeus subtilimanus and Anuroctonus pococki in separate terraria, and all are doing great. Keeping scorpions is a very fun and informative exercise, and have done wonders to give my family comfort with all things creepy crawly.

Posted by jaykeller almost 7 years ago

Great info Jay, really interesting. :)

Posted by susanhewitt almost 7 years ago

thanks for the update. You should give us some more pictures too

Posted by naturenate almost 7 years ago

Hi All. One year anniversary of discovery! He is doing very well and happy as a scorpion can be. I'll work on getting some additional photos up after returning from AZ in early September following the iNat-athon.

Posted by jaykeller almost 7 years ago

@jaykeller Any updates? I also wonder if a double tail is a rare genetic mutation, perhaps if it bred a small number of its offspring would carry the (Presumably) recessive gene that causes it?

Posted by cliygh-and-mia over 6 years ago

It may take a very long time for it to re-occur, especially if it is recessive. When bred, around half of the genetic material is transferred to offspring (and that selection differs individually, so not all offspring would have the same genes). If you can get others from that parent with double tails, you may be able to start selectively breeding the trait.

Also if it is recessive, it might take a couple of generations to show up in offspring. For instance, say this scorpion has the recessive gene "n", you would need at least two offspring with the "n" gene. Then pair those, and hope to get the "double" n, which would produce two tails.

There are a lot of factors, so it isn't always as simple as the above.

Posted by silversea_starsong over 6 years ago

Wow! Please don't let one of these crawl into the house from my backyard... PLEASE please. LOL although I respect them as a species and find them fascinating, they still scare me to death. TWO stingers instead of one? AAAAAaaaaaaa!

Posted by vwls almost 6 years ago


Sadly, she passed away overnight, so this will be the final update. It appears she developed some sort of intestinal blockage right at the tip of her abdomen at the bases of the two tails that could not be rectified. I have to wonder whether her structural abnormalities were partly the cause. A few days ago I gave her two crickets in her terrarium, and she stung and started eating one, then while still consuming the first, stung and held onto the second with her other, partly malformed chela, eventually consuming that one too! While that sounds amazing, it was actually something I saw her do multiple times over the past 25 months that she was in captivity. The potential exists that one of the (national chain pet store) crickets was also carrying disease, which has always concerned me.

At any rate, I learned a lot about Arizona Bark Scorpions during this time, and will value having had the opportunity to find and observe this fascinating specimen. I view this as a once in a lifetime opportunity to study this phenomenon, and I feel I made the most of it. She is safely preserved in ethanol, so she can be observed and studied by others for many years to come. I will hold onto her for the time being, but will eventually donate her to an institution of my choosing.

Thanks to all of you who followed this thread, and for your interest.

Posted by jaykeller almost 6 years ago

Thanks so much Jay. You did well to keep her alive for 25 months.

Posted by susanhewitt almost 6 years ago

I second Susan's comment. Thanks for letting us tag along here during this time. It's been fascinating.

Posted by jmaughn almost 6 years ago

I too really enjoyed getting these updates, Jay.

Posted by sambiology almost 6 years ago

Quite a specimen! You kept it alive longer than any institution would have done! Thank you for sharing all your experiences and observations pertaining to this fantastic individual.

Posted by naturenate almost 6 years ago

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