In this study we tested the nature of the phoretic relationship between the cosmopolitan mite Macrocheles merdarius and the dimorphic dung beetle Onthophagus binodis. We observed and experimentally manipulated the number of mites on individual beetles and tested how mite infestation affects male longevity. There was a significant effect of mites on male longevity: males in our mites-added treatment died on average 15 days earlier than males in our mites-removed treatment. Interestingly, the number of mites on males was significantly repeatable suggesting that individuals may differ in their susceptibility to infestation. Major males had more mites on them than minor males, and the proportion of mites on minor males was negatively density dependent.
