Tay Meadows Tidbit – Pseudoscorpion

Pseudoscorpion, Chelifer cancroides

When I went to brush my teeth last night, I noticed this guy hiding behind the faucet. I put down my toothbrush and hurried to grab my camera and macro lens instead. The macro because it’s tiny, perhaps just half a centimetre (less than 1/4″). He was pretty obliging about hanging out for some photos, and the white porcelain sink made a nice, uncluttered background.

The critter is a pseudoscorpion. As you might guess by the number of legs on the body, pseudoscorpions are relatives of spiders, also found in Class Arachnida. Like spiders, they produce venom and silk, although the venom is injected through the pincer, and the silk is produced by a gland in their jaws rather than on their abdomen. Although they look just like scorpions without a tail, the similarity is superficial, as scorpions belong to a different Order (Scorpiones instead of Pseudoscorpionida).

Pseudoscorpion, Chelifer cancroides

There are some 3300 species of pseudoscorpion around the world, with potentially upward of 350 species in North America north of Mexico. Most of the diversity occurs farther south; up here there are probably fewer than 50 species that occur in Canada. They are found in virtually every habitat, from the deserts of the southwest to the northern taiga and tundra. There is one species that is so closely tied to human settlement that its habitat is described as “Houses, building, barns”, and is “often found crawling on the walls of older homes, particularly in humid locations”. That species would be Chelifer cancroides, and is the species that I believe my pseudoscorpion to most likely be, although apparently being able to definitively tell the difference between it and another Chelifer species requires being able to count the setae (hairs) on the pincer and examine the venom gland.

Pseudoscorpion, Chelifer cancroides

Also superficially resembles a crab, except crabs have tails that curl underneath their abdomens. No tail on this guy. (This is his underside. I flipped him gently with a Q-tip for this photo.)

When prodded, the pseudoscorpion goes into a defensive posture, pulling its pincers back toward its body. Its pincers aren’t limbs in the traditional sense, but are actually modified palps, mouthparts, much the way male spiders have swollen “mitts” in front of their faces. They use the palps primarily for hunting, stinging and immobilizing the prey with the venom gland located on the thumb-like inner pincer (the outer one is fixed). They apparently do not ingest the prey whole, but rather secrete digestive enzymes onto the prey and then “suck up” the liquified remains (this isn’t that different from the dietary habits of a spider, except the spider usually wraps its prey up with silk, first). Pseudoscorpions prey on dust mites and book lice, so are good to have around the home. Once it reaches maturity, an individual may live as long as two to three years.

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27 responses to “Tay Meadows Tidbit – Pseudoscorpion

  1. Keeping the household Pseudoscorpion population high is another good reason to not clean house too often or too thoroughly.

  2. Never heard about this group before…
    Here in Belgium seem to live 10-15 different species, all of the smaller kind (around 2 mm), that are only to be distinguished by microscopy.

    Thanks for telling about this intriguing thing!

    • That seems to be the case with so many groups of invertebrates, Anne – only separable with a microscope. Fortunately, unless you’re a professional scientist, it’s rarely necessary to reach that level of detail in one’s identification.

  3. At first I thought this was some sort of tick. Thanks for explaining that this creature is an ally, not an enemy.

    (Btw, you’re mentioned in my post, “Branch Membership”. I hope you’ll drop in and say hi.)

  4. Great photos. You never know who might wander by while you’re brushing your teeth!

  5. Adorable, unless you’re a book louse, I suppose.

  6. Gorgeous shots! I’m always more than happy to find one or more of these little critters in the house. (And I like Marvin’s logic!)

  7. That’s such a great find! I have only seen one in India by sheer luck. Thank you for sharing this wonderful, less known cute fella with us!

    These creatures are also known to hike a ride on winged creatures such as cockroaches, beetles and bees to travel elsewhere.

    • Apparently they can be found in forests and the like by examining dead logs and such, Ani, but I’ve just happened to come across all the ones I’ve seen in my house. He is rather cute, eh?

      I didn’t know that about them hitching rides. That’s some impressive ingenuity for an invertebrate!

  8. It is so cool to think that pseudoscorpions (and not scorpions!) can be found in our part of the world.

    • Isn’t it, Mike? And yes, I’ll take these guys over real scorpions any day. :) Although, I must admit, seeing the scorpions glow under black light when I was in Arizona *was* pretty cool…

  9. On first sight, this is something I’m sure most folks would squish. It is rather scarey looking. But when you read that these guys eat dust mites (hooray!) and book lice (yea!), they are suddenly desireable around the house. Hm…wonder where I can get me some…

    Nice pics!

  10. I saw one of these guys on my monitor the other day. Though they look a little creepy up close they’re kind of cute when seen with the naked eye, being so tiny with their little waggling pincers. I left mine alone.

    • Hee. That’s a funny encounter, Fiddlegirl. Was he waving hello? :)

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  11. Another women who appreciates the beauty of a pseudoscorpion :)

    Love it :)
    Om shanti,
    Roberta

  12. Thanks for posting about this. My friends and i were at the beach this past Sunday and one of my friends found one of these in his shoe. Small and black…no one had any idea what it was so i did the research and found this.

    Are these normally found at the beach? We live in northern California. We were by Montara State beach off highway 1.

  13. I live in southwestern Pa. We moved into a new house, that has been vacant for 2 years, and did some remodeling. We have found these 4 of these insects in our upstairs bathroom within the last 3 months. They remind of ticks. Ours are alot darker/almost black. Are these harmful?

  14. I ran into one of these during an archeological dig in northern California. My grandfather, a third generation Californian, called it a “brigadoon” but I have found no reference to this “common name”.

  15. I found one this morning in the shower…freaked me out and I flushed him…now that I know better I won’t flush another! Thanks for your post!!!

  16. Just found one and got some pictures.

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