How the Blow-fly Flies and Why Engineers Are All Excited About It

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Iron Man, bow your head: the humble blow-fly can outdo you without even blinking. Not that it can blink. Now scientists know how.

A team from Oxford, the Imperial College London and the Paul Scherrer Institute attached an unhappy insect to a plinth. The plinth was then rotated while the fly beat its wings, presumably hoping to do something more useful to itself, like flee or find food.

Meanwhile, its movements were scanned by X-rays, courtesy of powerful new X-Ray technology at PSI.

The scientists thus saw, for the first time, the muscle mechanics of the blow-fly in action, thereby opening doors to the future development of micro-aircraft modelled on the insect's flight mechanics.

The blow-fly (Calliphora vicina) can beat its wings about 100 times a second. That is incredibly fast. (By the way, it isn't the fastest: the fruit fly, another favorite subject of scientists, can achieve 250 beats a minute.)

The team filmed the insect's muscles in action, providing a glimpse into the inner workings of one of nature's most complex mechanisms, the blowfly's flight motor.
The scientists say the movies could inspire new designs of micro air vehicle and other micromechanisms. In theory.

"The thoracic tissues block visible light, but can be penetrated by X-rays," Dr Rajmund Mokso from the PSI explained their visual coup. "By spinning the flies around in the dedicated fast-imaging experimental setup at the Swiss Light Source, we recorded radiographs at such a high speed that the flight muscles could be viewed from multiple angles at all phases of the wingbeat. We combined these images into 3D visualizations of the flight muscles as they oscillated back and forth 150 times per second."

The flies responded to being rotated by trying to turn in the opposite direction, allowing the scientists to record the asymmetric muscle movements associated with turning flight.

Professor Graham Taylor of Oxford University's Department of Zoology, who led the research in Oxford, says the insect uses its flight muscles in much the same way as a car is designed to use its differential.

"Whilst the power delivered to the fly's wings on each side remains the same, the fly effectively 'brakes' on one side by diverting excess power into a steering muscle specialized to absorb mechanical energy," he said.

The X-rays demonstrate how the power and steering muscles in the fly's thorax work, "to enable stunningly aerobatic flight manoeuvres unmatched by any manmade device," said Professor Holger Krapp from Imperial College London's Department of Bioengineering. "Our study opens up the opportunity to uncover how the fly controls its sophisticated flight engine using the signals from different sensors and a brain no larger than the size of a pin head."

A report of this research, including the 3D movies, appears in this week's PL0S Biology.

The humble Calliphora vicina, also known as the blow-fly: Pest, or inspiration for engineers?Credit: Aleph, Wikimedia Commons
X-rays clearly show the muscular structures of the fly.Credit: Reuters

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