Figure 1.

Flower tracking in hawkmoths. We investigated the flower tracking performance of three hawkmoths species with different diel activity patterns (a). Black dots denote experimental light intensities. Illuminance in (a) was measured at the position of the flower, facing the light source, while luminance was measured from the flower face at a distance of 2 cm. Moths tracked and fed from robotic artificial flowers (b, example from D. elpenor; see the electronic supplementary material), moving in a combination of sines of different frequencies (c). The Fourier transformation of the tracked flower shows the stimulus frequencies and amplitudes (c), which were chosen to give equal velocities across frequencies. We used a system identification approach to describe the closed-loop behaviour of a moth's flower tracking (d). The inner part of the closed loop contains the nervous system (sensory and motor circuits) and the mechanics (body and wings). A simple time delay, as well as scaling factor, can be added to the inner part of the loop to model adaptations of the nervous system at different light intensities or across species.