Introduction: Pseudoscorpions is a flattened, oval, brown, black or brownish-green colored arthropod with a short fang-like appendage in front of its mouth (chelicerae). The appendage has a fixed and movable finger that allows the “scorpion” to grasp items. Also, like most arachnids it has a pedipalp, which is a pincer-like claw capable of clasping and crushing prey and secreting poison from a gland (1). Unlike the common scorpion it does not possess a long tail and is unable to sting other organisms. It is a small organism that usually reaches 5 millimeters, even though one species is capable of reaching 12 millimeters (3). Pseudoscorpions have spinnerets that allow them to produce silk for the construction of nests. On average females produce three to four clutches of eggs at a given time. The female carries her eggs until the young hatch. Although the lifespan of the Pseudoscorpions is unknown, it is believed that the adult can live anywhere from six months to two years.
How do these two organisms relate? Pseudoscorpions have established mutual relationships with birds and rodents (in this case packrats) by consuming other arthropods that invade the nest. Some species are phroretic- live on beetles and large insects, where they feed on mites in return for increased motility.
 Cost/ Benefit Analysis: In a phoretic relationship, the transporter gains nothing, while the other organism gains motility. According to The Art of Being a Parasite the Pseudoscorpions can become a burden on the transporter if too many passengers were to climb on board the beetle (6). However, it was observed that the Pseudoscorpion lives in the nest of the rodent. The Pseudoscorpions eats packrat ectoparasites (i.e. larval and adult fleas) and finds a place of shelter from predators, namely for reproduction. The packrat in turn receives relief from fleas, which are a nuisance because they can cause changes in the behavior of the rat, weight loss, and fur loss. All of which reduce the health of the rat, making it more vulnerable to pathogens. There is no cost incurred from this association.
6. The Art Of Being a Parasite