Plant surfaces showing hierarchical structuring are frequently found in plant organs such as leaves, petals, fruits and stems. In our\r\nstudy we focus on the level of cell shape and on the level of superimposed microstructuring, leading to hierarchical surfaces if both\r\nlevels are present. While it has been shown that epicuticular wax crystals and cuticular folds strongly reduce insect attachment, and\r\nthat smooth papillate epidermal cells in petals improve the grip of pollinators, the impact of hierarchical surface structuring of plant\r\nsurfaces possessing convex or papillate cells on insect attachment remains unclear. We performed traction experiments with male\r\nColorado potato beetles on nine different plant surfaces with different structures. The selected plant surfaces showed epidermal\r\ncells with either tabular, convex or papillate cell shape, covered either with flat films of wax, epicuticular wax crystals or with cuticular\r\nfolds. On surfaces possessing either superimposed wax crystals or cuticular folds we found traction forces to be almost one\r\norder of magnitude lower than on surfaces covered only with flat films of wax. Independent of superimposed microstructures we\r\nfound that convex and papillate epidermal cell shapes slightly enhance the attachment ability of the beetles. Thus, in plant surfaces,\r\ncell shape and superimposed microstructuring yield contrary effects on the attachment of the Colorado potato beetle, with convex or\r\npapillate cells enhancing attachment and both wax crystals or cuticular folds reducing attachment. However, the overall magnitude\r\nof traction force mainly depends on the presence or absence of superimposed microstructuring.
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