Meeting Abstract
In almost all insects the wings are powered through two antagonistic groups of flight muscles. These indirect power muscles are so called because instead of inserting directly onto the wing, they instead attach onto the thorax. They produce tiny, linear strains that cause the thorax to deform in such a way as to amplify and transform this movement into the much larger, angular motion of the wing via the complex wing hinge. We currently have a poor understanding of how this intricate mechanism works. This is in large part due to the extraordinary difficulty in measuring micrometre-scale muscle movements in vivo at frequencies in excess of 100 Hz. Here, we used synchrotron-based, time-resolved microtomography to visualise the three-dimensional movement of the flight motor of blowflies (Calliphora vicina) during tethered flight. We then tracked the movement of power muscle end points, flexure regions on the thorax, and the wing hinge sclerites to create a kinematic model of the flight motor. The results show that the insect thorax can be modelled as a rigid four bar linkage, which captures the movement of the thorax and muscle strains. Despite attaching to the same linkages, the slight differences in orientation of the two sets of power muscles results in antagonistic effects on the linkage model. The four bar linkage allows the linear strains produced by the muscles to be converted into an angular motion, but with only a small amount of amplification. Instead, the movements are transmitted to the wing hinge via the scutellar lever and it is there that the angular motion is mostly amplified. However, the wingtip amplitude is still considerably larger than that of the wing hinge, indicating that much of the wing motion is caused by passive aeroelastic effects.
