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May 22, 2014

How does a fly steer in flight?

An illuminating article by Brady Dennis in the March 25 Washington Post explained "how the fly's tiny steering muscles, which make up less than 3% of its total flight mass, influence the output of the much larger muscles that power its flight."

Below, a three-dimensional visualization of the insect thorax.

The video's YouTube caption:

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The muscles are shown for the high-amplitude (left) and low-amplitude (right) wings through ten stages of the wingbeat, starting at the beginning of the downstroke. The steering muscles are viewed from the inside of the thorax looking out toward the wing hinge, and other parts of the thorax have been removed for clarity. The view of the low-amplitude (right) wing muscles has been mirrored about the sagittal plane of the insect for ease of comparison. The basalare sclerite is not visible directly in the reconstruction, but its position can be inferred by the intersection of the b1 and b3 steering muscles. See article for labelling of muscles. This is Movie S2 from the article.

Citation: Walker SM, Schwyn DA, Mokso R, Wicklein M, Müller T. et al. (2014) In Vivo Time-Resolved Microtomography Reveals the Mechanics of the Blowfly Flight Motor. PLoS Biol 12(3): e1001823. doi:10.1371/journal.pbio.1001823

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Below, excerpts from Dennis's story.

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It's now possible to see exactly how the lightning-fast insect weaves its way through the air. Using a new 3-D X-ray scanning technique, researchers were able to offer a virtual glimpse at the inner workings of one of the more complex mechanisms in nature — the flight motor of a tiny blowfly.

"The key question is how the fly's tiny steering muscles, which make up less than 3% of its total flight muscle mass, influence the output of the much larger muscles that power its flight," Graham Taylor, a professor at Oxford University’s Department of Zoology, said in announcing the findings, which appear in the most recent edition of the journal PLOS Biology. Taylor said researchers discovered that the flies essentially turn much the way a car does. "The fly effectively 'brakes' on one side by diverting excess power into a steering muscle specialized to absorb mechanical energy," he said.

Those complex movements happen quickly. In the time that it takes a human to blink, researchers said, a blowfly can beat its wings 50 times. Because its wings contain no muscles, each movement is controlled by tiny steering muscles — some as thin as a human hair — hidden out of sight within the thorax. To record those concealed movements, researchers spun the flies around inside a Swiss laboratory. The insects reacted to being spun around by trying to turn and fly the opposite direction, allowing the researchers to capture X-ray images of their flight muscles in action from all angles. Those images were converted into 3-D visualizations, created a virtual video of the inner workings of flies in flight.

"For the first time, we can visualize how the power and steering muscles in the fly’s thorax work to enable stunningly aerobatic flight maneuvers unmatched by any man-made device," Holger Krapp, a faculty member at the Imperial College London's Department of Bioengineering, said in a statement. "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."

Taylor said researchers hope the findings ultimately could be as practical as they are fascinating, "the development of new micro air vehicles and other micromechanical devices."

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Up top, a second three-dimensional rendering of a fly's thorax.

Below, the YouTube caption of the video up top.

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This video shows the insect thorax reconstructed from tomograms and highlights the external movements of the thorax and the location of the indirect power and steering muscles. This is Movie S1 from the article.

May 22, 2014 at 08:01 PM | Permalink


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