Sexual dimorphism in the attachment ability of the ladybird beetle Coccinella septempunctata on soft substrates

Heepe, Lars, Petersen, Dennis S., Tölle, Lisa, Wolff, Jonas O. and Gorb, Stanislav (2017) Sexual dimorphism in the attachment ability of the ladybird beetle Coccinella septempunctata on soft substrates Applied Physics A, 123 (1). DOI 10.1007/s00339-016-0684-5.

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Supplementary data:

Abstract

Many insects possess adhesive foot pads, which enable reliable attachment to diverse and unpredictable substrates. The function of these adhesive organs was shown to be affected by environmental conditions such as substrate roughness, chemistry, and ambient humidity. So far, the attachment ability of insects and also that of spiders and geckos has been tested on rigid substrates only. However, the natural habitats of climbing animals may provide a variety of substrate stiffness ranging from rigid rock surfaces to soft, biofilm covered substrates. In order to test the effect of different substrate stiffness on the attachment ability of insects, we have performed friction experiments with female and male ladybird beetles Coccinella septempunctata on smooth silicone elastomer substrates of different stiffness, using a centrifugal force tester. Whereas in females, the attachment ability was not affected by the substrate stiffness within the range of tested stiffness, males showed decreasing attachment ability with decreasing substrate stiffness. This sexual dimorphism in attachment ability is explained by the presence of a specialized, discoidal seta type in males, which is not present in females. It is argued that discoidal setae, when softer if compared to the substrate, may show an advantageous peak-free interfacial stress distribution when being pulled off the substrate. For such setae being stiffer if compared the substrate, they potentially show increased edge stress concentration. In this case, lower pull-off forces are expected, in agreement with the experimentally obtained results. With the present study, we demonstrate for the first time that the substrate stiffness may have an effect on the attachment ability of climbing animals, which may also be of relevance for technical and medical applications involving adhesion to soft substrates.

Document Type: Article
Keywords: Beetles Attachment Substrates Stiffness Insects Adhesives Animals Stress Concentration Sppiders Biofilms Centrifugal Force Habitats Silicones Elastomers Test Equipment Organs
Research affiliation: Kiel University > Kiel Marine Science
Kiel University
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
DOI etc.: 10.1007/s00339-016-0684-5
ISSN: 0947-8396
Date Deposited: 10 Jan 2018 13:24
Last Modified: 10 Jan 2018 13:24
URI: http://eprints.uni-kiel.de/id/eprint/41377

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