Hover flies lack gravity sensors

The screaming on most rollercoasters begins almost as soon as anticipation of the stomach-churning descent begins. Even in the dark we know that we are plummeting from the instant we tip over the summit, and the secret of the thrill lies deep in gravity sensors in our inner ears and intestines. As soon as the descent is launched and we begin free falling, the effect of gravity on the sensors is eliminated, producing the familiar stomach-churning sensation. However, Stéphane Viollet, from the CNRS and Aix-Marseille University, France, explains that the feedback from gravity sensors can sometimes be misleading and in some circumstances they may even fail if a manoeuvre is particularly extreme, saturating the receptors so that they no longer respond. Knowing that hover flies are extraordinarily agile and routinely perform aggressive high acceleration manoeuvres, Viollet and colleagues Roman Goulard and Jean-Louis Vercher wondered whether the insects rely on gravity-sensing organs to detect when the world has fallen away from beneath their feet.