Climbing of leaf trichomes by eriophyid mites impedes their location by predators

Eriophyid mites are plant parasites that are well adapted to hide away from predators. Tiny and wormlike, they can invade very narrow spaces in plants or form galls that, apart from other functions, serve as a shelter from predation. Previous observations showed that some free-living eriophyids as well as tetranychid mites spend their quiescence on the top of leaf trichomes. Here, I investigated climbing leaf trichomes by the eriophyid, Rhinophytoptus concinnus, and tested whether it enables the herbivores to avoid phytoseiid mites. Climbing behavior took place just prior to the quiescent period of juveniles. Larvae and nymphs raised the hind part of their stiffening bodies and walked, turning around on their axis. Having found a hair, juveniles attached their anal suckers to its tip, and, pushing back from a leaf surface or the base of the hair, they lifted their bodies up to become motionless. As revealed by the playback experiments with the phytoseiid mite, Typhloctonus tiliarum, predatory females needed much more time to find quiescent nymphs perching on hairs than those placed on a leaf surface. The time of nymph handling was similar in both situations. Also, a similar number of predators gave up feeding on nymphs in both locations. I conclude that climbing leaf trichomes enables the herbivorous mite to hide from predators. After detection, however, placement on trichomes does not give the quiescent juveniles any advantage over those placed on a leaf blade.