PSEUDOSCORPIONS

By Arthur V. Evans

Some of my most memorable natural history moments were the result of serendipity — that wonderful mix of directed activity and pure chance that results in unexpected discovery. Recently, I enjoyed the fruits of yet another serendipitous event.

While crouched down on a bed of dry, brown leaves laid down the previous autumn, I peered through my camera’s lens to capture the image of a rather plain, charcoal black beetle not-so-distantly related to that familiar denizen of pet stores and bait shops, the mealworm. With my macro lens fully extended just inches away from my subject to capture an image nearly twice life-size, I rocked my body slowly back and forth in tiny increments to find the “sweet spot,” that point where every part of the beetle snaps into razor-sharp focus and I trip the shutter.

As I peered through the lens a soft, tiny, pale arachnid less than one eighth of an inch peered out from underneath the heavily armored body of the beetle for just a second before disappearing. It suddenly reappeared on the beetle’s back, and then ran several laps over its heavily armored surface before dashing out of side. Seconds later it dashed out into the open and quickly disappeared into a hairline crack in the log, but not before I managed to fire off two shots.

With scorpion-like claws and lacking a tail or stinger, I immediately recognized this minute and speedy arachnid as a pseudoscorpion. Most of the world’s 2,000 or so species of pseudoscorpions live in the tropics, but about 350 species make their home in the United States and Canada.

Pseudoscorpions use their enlarged pincer-like claws for locating and capturing animal prey even smaller than themselves, such as springtails and mites. Although they have four simple eyes, their vision is weak. Instead, they rely on long, sensitive hair-like structures on their claws to find their prey. The hapless victims of pseudoscorpions are quickly dispatched and liquefied with venom produced by special glands in the claws that oozes into the victim’s wounds.

They generally live beneath stones, in moss or leaf litter, under bark, or in animal nests. Some live along the seashore, hunting between the tide lines for prey. Others prefer to live inside caves. One species, the house pseudoscorpion, is commonly found in human habitations.

Small and wingless, travel for pseudoscorpions from one food source to the next over long distances is no minor obstacle. Many species have managed to get around this hurdle by using insects, especially larger beetles, for transportation. Longhorn and scarab beetles unwittingly carry these tiny hitchhikers on their legs and underneath their wings without any ill effect.

Like some other better-known arachnids (e.g., spiders), pseudoscorpions are capable of manufacturing silk. Equipped with silk-producing glands in their mouthparts, they will build silken retreats for hibernation, molting, and egg production. Venom is produced strictly for prey capture and does not pose any danger whatsoever to people or pets.

Courtship varies among pseudoscorpions. Males generally deposit a single sperm packet on the ground and are picked up by the female. Some females locate the packet by touch and smell, while others follow a silk line left by the male as a guide. In some species the male grasps the claws of the female and drags her over the packet. Prior to laying her eggs, the female must build a protective silken retreat.

To build the retreat, the female lays down silk in a ring and continually adds smaller and smaller rings until a protective dome is formed. Some species may adorn these structures using bits of debris. Safely tucked away, she lays her eggs inside a clear sac and attaches it to the underside of her abdomen.

The young molt before hatching and will not leave the sac until the third molt. One or two generations are produced each year. As many as 50 or more young are produced in each generation.  They reach adulthood in about a year and, depending on the species and circumstances, may live two to five years.

© 2010, A.V. Evans

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9 Responses to “PSEUDOSCORPIONS”

  1. I’ve only ever encountered one pseudoscorpion. The sad thing is I did not know I had encountered it, until I took the pictures off the camera and was editing them. This tiny little scorpion-wanna-be was attached to the side of an Ivory-Marked Longhorn Beetle. Had I realized this hitchhiker was present I would have taken great care to get images of it as well. As it is I have a blurry, sorta-looks-like-a-pseudoscorpion image…LOL

  2. […] found, people generally agree that pseudoscorpions are pretty astonishing to watch.  Check out this blog on […]

  3. Joan Usher Says:

    Just found one on our counter=top? where a small house-plant had been sitting.
    We had just taken a tick off of our dog there, this morning. Did it come from the plant? or the dog?
    It moves very quickly, and is very ‘aware’ of it’s surroundings. I finally let it free outside, although it is quite cool at this time of the year. (Sharbot Lake, Ontario, 1 hr north of Kingston)

    • There is a species known as the house pseudoscorpion that typically lives indoors.

      • Katie Brees Says:

        Each spring and Fall I experience a remarkable (to me) occurance that may be attributed to house pseudoscorpions. Perhaps you can help.

        3 years ago we found 5-8 little teardrop shapped white silken “purses” laying on our carpet hallway. All empty except one I found hidden away from the others. When I peeked inside, a group of shiny bright little spiders looked out at me as though they were on a camping trip. I know I am anthropramophesising badly here, but they gave off a very “happy to see you” feel. Not the least afraid. I put them gently back where they lay, not realizing what I had. But knowing it was very unlikely capable of hurting me, or my animals. These are very, very small. (2mm Tops.)

        Now each spring and fall, they zip around…Two large front arms looking like ocean crabs.
        But there are several other behaiviors that astound me. Do you know someone I could email the details to; who would be interested, and let me know if indeed these are pseudoscorpions, or perhaps a cousin I’ve miss identified?

        Thanks,
        Katie

      • Not sure without a photo or specimen, but these sound like caterpillars of case-bearing clothes moths . What do you think?

  4. i still don’t like the (house centipedes) because to me they just look nasty and the sting or bite does hurt bad it feels like a knife going into your skin at first then it feels itchy then sore for awhile i would rather be stung by a bee then by a centipede i just don’t see how frogs and turtles can eat these but they do

  5. i have question i caught a big bug that was flying by the light outside and it looks like a dragonfly but its brown with clear wings and big pincher’s on its head anyways it might be one of these bugs “Raphidioptera” or related to them i don’t know

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