Visualization of the Number of Tarsal Adhesive Setae Used During Normal and Ceiling Walk in a Ladybird Beetle: A Case Study
The hairy attachment devices of climbing animals consist of hundreds to billions of micro- to nanoscopic adhesive setae which can form an intimate contact with the substrate and thus allow for sufficient adhesion to walk on vertical walls or even on the ceiling. In previous studies, the combination of microscopic visualization of the pad morphology and adhesive force measurements at the level of individual setae aided in the estimation of the maximum adhesive capability of different animals by assuming all setae being in contact with the substrate. These estimates, however, did not necessarily coincide with adhesion measurements performed at the level of the whole animal. We hypothesize that this discrepancy may arise due the fact that not all setae are simultaneously applied during locomotion. To test this hypothesis, we visualized the number of adhesive setae used during normal and ceiling walk in a ladybird beetle. We found that ladybird beetles had significantly more setae in contact with a smooth substrate during ceiling walk than during normal walk. Moreover, during ceiling walk mainly spatula-shaped setae were used during locomotion, which are expected to provide high adhesive forces.
We would like to thank Felix Schönmuth and Alexander Massing for their help with the acquisition of video sequences and sequence analysis and Bastian Poerschke for his assistance in the data analysis.
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