In situ visualization of spider mite-plant interfaces

The cosmopolitan and polyphagous two-spotted spider mite Tetranychus urticae (Acari, Tetranychidae) exhibits a remarkable host plant range. A cryo-scanning electron microscopic study of T. urticae in contact with selected hosts was conducted, demonstrating the universal attachment of pretarsi to a variety of plant surface types, including crystalline waxy, glandular, and non-glandular hairy, as well as non-wettable and wettable surfaces. Similar to spiders and geckos, T. urticae bears a dry hairy attachment system. Beside the six empodial hairs (setae), each leg is equipped with four tenent (adhesive) setae with multi-part spatulate terminals (subunits), independent of the developmental stage. The cryo-scanning electron micrographs clearly demonstrate the formation of intimate contact between spatulate tips and substrates. Results are discussed in the context of arthropod attachment and arthropod–plant interactions.