Locusts take the strain with veins waiting in the wings

Fri, Aug 24, 2012, 01:00

BUGS MIGHT look small and vulnerable but they are made of tough stuff. Researchers at Trinity College studying the desert locust have discovered just how tough, learning how their apparently flimsy wings can carry them vast distances without breaking up.

Insect body parts, including the wings, are made of cuticle, one of the toughest natural materials in the world, said Prof David Taylor who, with Dr Jan-Henning Dirks in Trinity’s department of mechanical and manufacturing engineering, decided to study the locusts.

These are no ordinary insects. They can cover 100km a day and can fly for thousands of kilometres, Dr Dirks said yesterday.

“There are reports of them crossing the Atlantic Ocean. That is why we looked at these guys; they are like marathon-flyers.”

They focused on the wings given their critical importance in covering these distances. “If you are a locust with these super-thin wings you have a real problem if you get a crack in it,” said Dr Dirks.

For that reason the pair were taken aback when their first experiments showed the wing membrane was quite fragile and tore easily.

They then used video recordings to study how a crack spread from a small starting break, discovering that the crack stopped once it hit one of the veins that criss-cross an insect wing.

They found these crack-halting barriers increased the toughness of the wing by about 50 per cent. This helped to protect the wing span needed to sustain long distance flight.

Details of their work are published this morning in the online open journal PLoS ONE.

One might assume that if you are a locust the more veins the better if they can protect your wing, but the researchers found that it was not so simple.

The veins are thick and heavy compared with the wispy-thin membrane, which is only a tenth the thickness of a human hair. Too many veins means lots of weight, something that would handicap a marathon-flyer.

They found the biomechanical balance was “optimised” in the locust wing between heavy veins and lightweight membrane. It has enough veins to protect the wing but not so many that the wing never tore and the bug could not fly.

They suggest that the locust wing design could be applied in the development of “micro-air-vehicles”.