House Pseudoscorpion
What timing! I’d just gotten the camera mounted to take nice, high-magnification photos of tiny things, and then S. tells me there is a pseudoscorpion in the bathtub, just *begging* to be photographed. So, here it is:
Then, we flipped it over to have a look at the underside:
And then, finally, zoomed in on one claw:
Considering that this little guy was only about 3 mm long, I think the photos came out pretty sharp. We figured that this should be good enough to get a full, positive ID, so I found an identification key to the pseudoscorpions of Michigan in the MTU library[1] . . . and had my illusions pretty much dashed. It turns out that you distinguish pseudoscorpion species from each other based on very fine details of the claws, and where exactly the sensory hairs (setae) are located. Unfortunately, even though the claw detail photo is pretty good, it isn’t good enough to count setae. According to the author of the ID key, even an expert might take as much as a week to prepare, dissect, and examine a pseudoscorpion to determine the species. There are supposed to be at least 29 species in Michigan, so the next ones we find might get taken in to the lab for a more thorough examination.
While a really positive ID isn’t practical from these photos, the fact that it was in the house (and, specifically, in the tub) means it was almost certainly Chelifer cancroides, also known as the “house pseudoscorpion” or “book scorpion”. This is a “cosmopolitan” species, meaning that we have carried it around the world and it pretty much lives everywhere that humans live. They are actually very common, but are rarely seen except when they, say, venture into the bathtub to get water. They spend the rest of their time eating other, even smaller arthropods (mites, clothes moth larvae, and the like), and generally get dismissed as being harmless and of no economic impact. They are reported to live for 2-3 years, which is pretty good for such tiny creatures.
Even though they look superficially like scorpions, they are in a separate order (Pseudoscorpiones), and are about as closely related to spiders as they are to scorpions. Instead of poisoned tails, they have venom glands in their claws that they use to kill prey. Of course, at less than about 3 mm long even for the largest species, they are completely incapable of breaking the skin of a human, so their venom is irrelevant to us. Pseudoscorpions frequently get around by hitching a ride on other insects, like the one in this rather startling picture.
[1] Sigurd Nelson Jr., (1975), “A Systematic Study of Michigan Pseudoscorpionida (Arachnida)”, The American Midland Naturalist, Vol. 93, No. 2, April 1975, pp. 257-301
Hi! I just discovered your website today, while searching for some good sources of pseudoscorpion photos and resources. I’ve written a children’s article on these “bugs,” and am looking for an expert to check it for accuracy. I’m wondering if you could share the name of the contact who tried to ID this critter for you? Also, I would love to mention your photo as a possible supplement to the article when I submit it to mags.
Thanks,
buglady
I never actually spoke to or corresponded with him, but most of my information about pseudoscorpions came from Sigurd Nelson, who wrote this page on the Michigan Entomological Society’s “Entomology Notes” site. He is the only actual pseudoscorpion expert that I am aware of. Unfortunately, his contact information on the Entomology Notes page is obsolete, he isn’t at SUNY-Oswego anymore (I expect he is retired, assuming he is still alive). Sorry I can’t be more help here. You could try contacting the Division of Insects at the University of Michigan Museum of Zoology, there is a good chance that they can recommend someone.
Please go ahead and mention my photo as a supplement in your article, that would be fine.
These are such great photos. Before today, I hadn’t known that there were such insects; I found one among my books this morning and was trying to figure out what it is. Having just moved to this state, I find this website very helpful and interesting to say the least. Thank you!
Howdy from Painesdale. I just found one of these in my bathroom and was trying to id it online…little did I know the answer would come from a local source!
I have the subject in a pill bottle if you want it, otherwise I’ll release him to eat more dust mites!
I’m glad to have been helpful, my original plan was to be useful specifically to people near me, so it’s good to hear of a case where it worked that way.
I understand that pseudoscorpions don’t do well in captivity, and I don’t save dead specimens (it’s a lot of work and takes a lot of space to make and maintain a proper insect collection), so go ahead and let it go. Amusing little fellows, though, aren’t they?
hey Tim!
I just found this website while looking for a moth and then I noticed on your header was what I have named “Bob” because I had no idea what they were. I have been saving them from drowning in my shower since I first saw them. I am so happy to finally be able to know what my Bobs are ^_^ thank you for all the help! keep up the good work! If you like I have a video. It’s not the greatest quality because it was taken with a webcam. Here is the link:
http://www.youtube.com/watch?v=HzO6pTuOYFg
Heh. I didn’t really think that anyone would be able to make an identification from the header images. Maybe we need more than just one spider and a pseudoscorpion up there!
id recognize bob anyday
yeah maybe some more creepy crawlies up there