Pseudoscorpions are small arachnids with a flat, segmented, pear-shaped body. Despite being harmless and inoffensive creatures, this individual was able to move very quickly to escape. Pseudoscorpions got their name from a pair of huge pincers (pedipalps), resembling those of scorpions. But unlike true Scorpions they have a rounded abdomen that does not extend into a segmented tail with a stinger. The small creatures usually range from 2 to 8 millimetres (0.08 to 0.31 in) in length, with yellowish to red or dark brown colors.
Pseudoscorpions are generally beneficial to humans and prey on clothes moth larvae, carpet beetle larvae, booklice, ants, mites, and small flies. Chelifer cancroides is the most commonly found species in homes, where they are often observed in rooms with dusty books. They enter homes by “riding along” attached to insects (known as phoresy). A venom gland and duct are located in the mobile finger of the pincers (not shown). The venom is used to capture and immobilize prey. During digestion, a mildly corrosive fluid is poured over the prey to liquify the remains externally before they are ingested.
The “jaws” (chelicera; have a look at the beautiful structure shown in the center of the picture) are used to spin silk which is used to make disk-shaped cocoons for mating, molting, or waiting out cold weather. A comb-like structure (serrula externa) the yellow colored structure only visible in part on the inner rim of the chelicera (left hand side), is used for grooming. In the center of the chelicera is the other membrane structure which is called serrula interna. It helps to prevent food and fluids from escaping.
Also, two pairs of sensory setae can be found on the chelicera and additional structures which resemble plant pores are located on the cephalothorax (above the eyes; not shown on this picture). Scientists believe that the latter detect bending and stress on the cuticule and call them lyrifissures. Pseudoscorpions breathe through spiracles on their abdomen (not shown), a trait they share with the insects. Finally, most species have one (like this species) or two pairs of eyes that are equipped with only a few receptors. Whatsoever, some Pseudoscorpions lack external eyes completely and may use receptors underneath the cuticule to detect light.