Failed predation or transportation? Causes and consequences of phoretic behavior in the pseudoscorpionDinocheirus arizonensis (Pseudoscorpionida: Chernetidae)

The pseudoscorpion Dinocheirus arizonensisinhabits rotting saguaro cactus in the Sonoran Desert and has also been found attached to the legs of the cactophilic neriid fly, Odontoloxozus longicornis.Laboratory experiments demonstrated a higher incidence of phoresy on eclosing versus postteneral adult flies, a female bias in phoresy, and an increased rate in female phoresy through time. The pseudoscorpion may also prey on the fly, but predation rate was unaffected by fly category, pseudoscorpion gender, or food deprivation. A study of pseudoscorpion colonization in the field indicated that females were the first to colonize and the first to abandon the transient habitat of a saguaro rot and, thus, corroborated patterns of phoretic behavior in the laboratory. Taken together, these results establish that phoresy is a behavior functioning specifically for dispersal. The hypothesis that pseudoscorpion transport by other arthropods is accidental, motivated by hunger, and occurs because pseudoscorpions are incapable of consuming their hosts is rejected.