X-Ray-Generated Model Helps to Reveal How Flies Turn in Flight

We often take insect flight for granted and as casual observers, it’s hard to understand – flies move too fast and are too small for our limited eyesight. But a paper published recently in PLOS Biology provides beautiful and novel insights into how flies fly.

If you’ve ever tried to swat a fly, you’ll be aware of how easily they can take-off and how quickly they manoeuvre in mid-air, but how they performed such feats was previously unclear. Graham Taylor and colleagues at the University of Oxford and Imperial College London examined this by employing a technique called time-resolved X-ray microtomography. X-rays in a particle accelerator are used to create images of the cross-section of a small moving object, and these combine to build a 3D model. The method has been used previously to visualise larger animals, but this research was on a far smaller and faster scale of magnitude.

The chosen insect was a blowfly, which although small, is very agile. It can pull up to four times its own weight as it turns, and can beat its wings around 150 times per second. The fly was tethered to a rotating point, which made it turn in flight as X-rays were taken. From this, the researchers created an incredible virtual model of the fly.

See the model (Credit: PLOS Media, Youtube)

The research represents a real breakthrough in our understanding of how flies use the muscles in their thoraxes (they have none in their wings) to turn so nimbly. The model shows in detail five of the blowfly’s tiny ‘steering’ muscles, as well as its far larger ‘power’ muscles. It explains how variation in the wingbeat can allow energy to be absorbed on one side by specialised steering muscles, effectively ‘braking’ the fly on this side. Hence the steering muscles can execute the turn despite their small size relative to the power muscles. The power and steering muscles co-ordinate to resonate the entire fly thorax, and this deforming movement is translated via an intricate hinge to the wings. The whole complex mechanism enables the powerful, rapid and variable wingbeat which gives the blowfly its speed and agility.

The flight was simplified because of the tethering, and there is more work to be done in establishing the detailed mechanics of flight. However, this is an important starting point. Even if you’re not particularly interested in the precise mechanisms of fly flight, the innovative use of the X-ray microtomography technique on a tiny scale represents a methodological breakthrough. Hopefully, the model will inspire other scientists to use similar tools to better understand and represent their work.

But the findings have practical applications too – we could apply our insight into natural flight to aerospace engineering, to design flying machines controlled by motors as efficient as the blowfly steering muscles. Perhaps one day we’ll be able to build blowfly-planes which can swoop and dive as dexterously as the insect they’re inspired by. In the meantime, we’d better start improving our cures for travel sickness!

Full paper available at: http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1001823

View the model at: https://www.youtube.com/watch?v=P6lBkK3J9wg

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