Fly on the Wall

With a unique blend of science and humour, American naturalist and science educator Milos Radakovich is an extremely popular cruise ship lecturer.

He has written two volumes full of what he calls “Bite-size SCIENCE snacks” called 90 SECONDS. These articles were written to be delivered as 90 second radio spots. I have read and reread all many times.

If you are interested in ordering a copy or for more information e-mail Milos at milos@mbay.net

Fly on the Wall

How do they do it? Flies, that is…

how do they stick on window glass and walk on the ceiling? They seem to be defying gravity. Well, it is only a theory ☺

Still, it’s a remarkable feat. In fact, it is their remarkable feet that make it possible. Each foot has two broad adhesive footpads that give it plenty of surface area. The pads are equipped with tiny hairs, called setae, with spatula-shaped tips.

The setae are 1/1000 the diameter of a human hair and exploit the electrostatic forces between surfaces. Even though the forces are relatively weak, the cumulative effect of millions of setae is enough to generate considerable stickum.

Their feet sometimes have special curved claws at the end. We thought that they were used for holding on, but now it seems they are actually used like mini pry bars to help release their electrostatic grippers.

The pads also produce a glue-like substance made of sugars and oils. The thin layer of liquid increases surface area for better con-tact and even greater holding power. In fact, they sometimes stick so well, that insects would become immobilized were it not for the special structures and techniques for unsticking.

They can push or twist, but peeling their footpads free seems to require the least energy to break contact.

A research team from the Max Planck Institute in Germany recently studied more than 300 species of wall-climbing insects and watched them all leave behind sticky footprints.

Fruit fly

Fruit fly

 

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