We’ve all tried to swat a fly, only for it to escape onto the ceiling out of harm’s way and roam around, seemingly unrestrained by gravity’s effects.
This ability isn’t just limited to flies: a range of other insects such as cockroaches, spiders and ants seem to display similar abilities. This poses the question; how do they do it, and why can’t we? There are several factors that help insects cling to walls and ceilings, the first of which is that insects are much smaller than us in terms of mass. This means that the gravitational pull of the Earth has less of an effect on them then it would on us, making it a simpler task to overcome.
One of the ways they counteract this smaller force of gravity is through the use of tiny hooks on the ends of their feet pads, which are known as tarsi. These tarsi are flat, and similar in shape to a spatula. Using these tarsi, insects can hook on the tiny flaws in the surface they’re walking on. They also never lift more than two of their feet off the surface at any one time, ensuring a strong grip.
However, if the surface is completely smooth, like well made glass, with no tiny flaws or bumps to hold on to, these tarsi are rendered useless. This is why most insects also secrete a sticky resin made up of sugars and oils. Much like that on a sticky note, this resin lets them stick onto smooth surfaces without getting stuck permanently.
So what does that mean for us? Sadly, when it comes to climbing walls Spiderman style, smaller is better. Humans are too heavy, with hands too small to use the same gravity-defying techniques as insects. However, all is not lost, as scientists are now using this information to make wall climbing robots, the first of their kind.
So next time you jealously eye a fly walking along the ceiling know that, whilst we may never get to scale building like Spiderman, hopefully one day we’ll control robots that can.
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