This scanning electron micrograph shows the various adhesive hairs found on the footpad of the dock beetle (Gastrophysa viridula). The feet of the green dock beetle are covered with thousands of tiny adhesive hairs, each no wider than 5 microns (1/200th of a millimetre) across, that allow the beetle to climb, even over molecularly smooth substrates. Visible in the image are two distinct hair morphologies, both pointed hairs and hairs with flattened (disc-like) tips allowing the insect to peel each contact from the surface when it wants to detach. Recent research has shed new light on the mechanisms used by beetles and other insects to run across smooth surfaces.
A light microscope image taken at 50x magnification showing the measurement of single hair attachment forces from the footpad of a dock beetle (Gastrophysa viridula). Thousands of fine adhesive hairs are found across the feet of these beetles, allowing them to climb across smooth surfaces, such as a glass window pane or the flat surface of a leaf without needing their claws to hold on. In order to measure the attachment forces of a single hair, an experimental set up was developed using a fine glass cantilever (only 20 micrometres in width). This was lowered onto a single hair and then detached, with the resulting deflection recorded under high magnification. The forces measured from each hair are only a few hundred nanoNewtons; one millionth of the force required to lift an apple.
(Date of Image: 2006-2011)
Credit: James Bullock, University of Cambridge