The function of resilin in honeybee wings.

The present work aimed to reveal morphological characteristics of worker honeybee ( Apis mellifera ) wings and demonstrate the function of resilin on camber changes during flapping flight. Detailed morphological investigation of the wings showed that different surface characteristics appear on the dorsal and ventral side of the honeybee wings and the linking structure connecting the forewing and hindwing plays an indispensable role in honeybee flapping flight. Resilin stripes were found on both the dorsal and ventral side of the wings, and resilin patches mostly existed on the ventral side. On the basis of resilin distribution, five flexion lines and three cambered types around the lines of passive deformation of the coupled-wing profile were obtained, which defined the deformation mechanism of the wing along the chord, i.e. concave, flat plate and convex. From a movie obtained using high-speed photography from three orthogonal views of free flight in honeybees, periodic changes of the coupled-wing profile were acquired and further demonstrated that the deformation mechanism is a fundamental property for variable deformed shapes of the wing profile during flapping flight, and, in particular, the flat wing profile achieves a nice transition between downstrokes and upstrokes.