Herbivore Exploits Chink in Armor of Host

Abstract

Knowledge of plant-feeding mite diversity, their interactions with host plants, and their ecological impact are not clear or have been too narrowly studied in the past. The mite superfamily Tetranychoidea has been identified around the world feeding on almost every plant known. Spider mites (Tetranychidae) are the most common mite recognized by farmers, researchers, and any person with an ornamental plant at home. On the other hand, flat mites (Tenuipalpidae) are also common on plants, but are often overlooked due to their small size and camouflaging colors. Mites in the flat mite genus Raoiella Hirst are obligate plant parasites that feed via stylet-like mouthparts adapted to pierce plant tissues. A species of particular interest in this genus, the red palm mite, R. indica Hirst, is currently spreading aggressively throughout the Americas on species of palm (Arecaceae). How they feed on the plant and how they are able to multiply into huge populations on one host plant have only recently been studied. Here, using low-temperature scanning electron microscopy. R. indica and several other species in this genus were captured and observed for the first time feeding via the stomatal aperture of host plants in several different families. These findings on their different host plants challenged our common belief that all plant-feeding mites feed by piercing the epidermis. Stomatal feeding could negatively affect the plant's ability to regulate gas and water exchange. Further examination of feeding methods for other herbivorous mites is necessary.