Phoresy and Mites: More Than Just a Free Ride.

Mites are masters at attaching to larger animals, often insects, in a temporary symbiosis called phoresy that allows these tiny animals to exploit patchy resources. In this article, we examine phoresy in the Acari, including those that feed on their carriers in transit, from a broad perspective. From a phylogenetic perspective, phoresy has evolved several times from free-living ancestors but also has been lost frequently. Rotting logs appear to be the first patchy resource exploited by phoretic mites, but the evolution of rapid life cycles later permitted exploitation of short-lived resources. As phoresy is a temporary symbiosis, most species have off-host interactions with their carrier. These relationships can be highly complex and context dependent but often are exploitative of the carrier's resources or progeny. Transitions from phoresy to parasitism seem widespread, but evidence for transitions from obligate phoretic parasitism to permanent parasitism is weak.