Garrett B. Hughes
Pseudoscorpions
A small pseudoscorpion from the famly Cheiridiidae. This individual was collected from a mosquito in Yuma, Arizona.
Pseudoscorpions are also one of only 3 arachnid orders to produce venom. Spiders inject venom through their cheliceral fangs, scorpions through their stings, but pseudoscorpions inject venom through their pincers. The apical tooth of the pincers in pseudoscorpions from the suborder Iocheirata bears a small duct through which the venom is injected into prey.
With their small size, you might expect pseudoscorpions to hve trouble dispersing, but pseudoscorpions have solved the problem of long-distance dispersal through a technique called phoresy. This is when one organism uses another organism for transportation. Pseudoscorpions will use their pincers to hold onto the legs, hair, and bodies of larger organisms such as flies and beetles. These flying insects can travel much farther than a walking pseudoscorpion, so pseudoscorpions benefit greatly by hitching a ride on these insects.
As the name implies, pseudoscorpions bear a superficial resemblance to their cousins, the scorpions. Both have pincer-like chelae at the end of their pedipalps, and both have characteristics common to all arachnids: 8 legs, only simple eyes (no compound eyes), and chelicerate mouthparts. However, the physical similarities end there. Pseudoscorpions are much, much smaller. While the largest scorpions can be several inches, the largest pseudoscorpions rarely exceed a centimeter. Unlike their larger cousins, pseudoscorpions do not have their last abdominal segments elongated into a tail-like structure, nor do they bear the characteristic sting at the end. Yet pseudoscorpions possess amazing features that scorpions lack.
Only 3 orders of arachnids are known to spin silk, and pseudoscorpions are one of them. Pseudoscorpions spin silk out of the galea -- a spinneret at the tip of the fixed finger of the chelicera. Pseudoscorpion nymphs use this silk to create retreats for molting and adult females will create similar chambers for brooding. Because adult males do not need to molt and do not produce offspring, many males will have a proportionally smaller galea than juveniles and females. But some males do build silken chambers for enduring extreme environments, such as drought, heat, cold, and flooding.
