PSEUDOSCORPIONS PHORETIC ON A SPIDER 1 o "a C. Clayton Hoff and Daniel T. Jennings On 2 June 1969 Thomas R. Chacon, a U. S. Forest Service employee, found two female pseudoscorpions of the species Lustrochernes grossus (Banks) (Chernetidae) clinging to dorsal abdominal setae of a male giant crab spider, Olios fasciculatus Simon (Heteropodidae). The spider was collected from rnesquite litter in an area predominately of pinyon and juniper near Arizona State Highway 160, 2 miles northeast of Payson, Gila County, Arizona, elevation about 5000 feet. The species of spider is widely distributed in southwestern U.S. and has been reported from several localities in Arizona; the species of pseudoscorpion is common in Colorado, New Mexico, and Arizona. Except for being found beneath the elytra of cerambycid beetles taken in stands of ponderosa pine (Banks, 1902; Hoff, Jennings, and Pase, unpublished data), L. grossus has been reported (Hoff, 1956, 1959) as occurring invariably beneath the bark of ponderosa pine (Pinus ponderosa Laws.) logs, stumps, and snags. Spider and pseudoscorpions are deposited in the collections of the American Museum of Natural History. Phoresy involving pseudoscorpions on insects of several orders and on phalangids, birds, and mammals is common. Early records have been compiled by Vachon (1940) and Beier (1948). Strangely absent, however, are records of pseudoscorpions being found attached to spiders, and indeed a very careful search of the literature has failed to uncover a single record of pseudoscorpion-spider phoresy. This is in strong contrast to the many records of pseudoscorpions reported from phalangids (Vachon, 1947; Beier, 1948; Savory, 1966). We are inclined to follow Savory in thinking that the relationship of pseduoscorpion and phalangid is largely by chance. This does not aid in explaining, however, the occurrence of pseudoscorpions on phalangids and the apparent absence or rarity of pseudoscorpions from spiders. Habitatwise there should be as much opportunity for pseudoscorpions to contact spiders as there is for the animals to contact phalangids. We have considered possible explanations for the difference between phalangids and spiders with respect to pseudoscorpion phoresy. It seems feasible that the pseudoscorpion can cling very tenaciously to the slender leg of the phalangid by means of either one or both pedipalps, while the leg of the spider is too stout to allow the chelae to maintain a strong grip, although pseudoscorpions could certainly cling to the legs of small spiders and to the stout spines often present on the legs of some spiders. While phalangids frequently clean their legs (Cloudsley-Thompson, 1968), they must be unable or have no instinct to dislodge the pseudoscorpions. We considered the possibility that the phalangid does not eat pseudoscorpions and hence gives no attention to those attached to the legs, but Cloudsley-Thompson (1956) observed that while phalangids do not remove and eat pseudoscorpions from the legs, they do eat pseudoscorpions that by their own initiative drop from the legs. 'Accepted for publication: May 13, 1973. 2 Department of Biology, University of New Mexico, Albuquerque, NM 87131. 3 Rocky Mountain Forest and Range Experiment Station, USDA Forest Service, Albuquerque, NM 87101. Ent News, 85:21-22, 1974 21
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