CREATURES as small as fruit flies and as large as geckos stick to walls and ceilings using minuscule sticky pads on their feet called spatulae. Puzzlingly, the bigger the beast, the smaller the pads, and now researchers think they know why.
Spatulae probably work through a weak molecular force called the van der Waals interaction. Because larger animals weigh disproportionately more compared to their surface area than smaller animals, they need more spatulae to stick. So they make them smaller and pack them more densely. Flies have thousands, geckos have millions.
When Eduard Arzt from the Max Planck Institute for Metals Research in Stuttgart, Germany, and colleagues measured spatulae of various spiders, insects and geckos under an electron microscope they found that spatulae range from more than 2 micrometres in diameter in beetles to a mere 0.3 micrometres in lizards (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1534701100).
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