Earwax as pest control

Terrestrial mammals are constantly beset by insects, and the ear is a vulnerable point of entry. Unlike other body orifices that produce fluids such as mucus or tears, the ear appears defenseless. How does it stop invaders? We hypothesize that earwax acts as a slick barrier that prevents insects from crawling into the ear. In this combined experimental and theoretical study, we show that earwax is both slick and adhesive. Ants have difficulty climbing earwax-coated surfaces and cleaning earwax from their bodies. These phenomena are due to the hydrophilic, porous, and viscoelastic properties of earwax, which we study using microscopy, rheology, experiments with ants, and fabrication of arti earwax. We also demonstrate that earwax's aging renders it brittle, facilitating self-removal over a 10-week time scale. This study may be of use to designers of eco-friendly barriers for insects.