Understanding the mechanisms of insect flight
Flying insects can perform a wide range or aerial maneuvers better than any man-made flying device. Some insects can land upside down, change direction in a split of a second and engage prey in mid-air. To achieve such impressive capabilities, insects have evolved unique flight mechanisms, including a control system that exhibits the fastest reflexes in the animal kingdom.
Our goal is to understand these flight mechanisms. This challenge involves cutting-edge concepts in computer vision, machine learning, control theory, mechanical design, computational fluid dynamics, physiology and neuroscience.
Measuring pupil size and light response through closed eyelids
We developed a technology for measuring the size of pupils and their response to light through closed eyelids. These pupil parameters are key components in the neurological evaluation of comatose patients, for example after stroke or brain injury. Our method is based on side illuminating in near-IR through the temple and imaging through the closed eyelid. This technology has been successfully tested in a clinical trial and can be implemented as an automated device for continuous pupillary monitoring. Such a device may save staff resources and provide earlier alert to potential brain damage in comatose patients.
The bright spots in the figure are due to the near-IR light emanating from the eye through the closed eyelid. Imaging in invisible near-IR combined with illumination in visible white-light to induce the pupillary contraction reflex and image the pupil before and after contraction. Using a designated image processing algorithm, we then measure the pupil diameter dynamics as well as the scattering effect of the eyelid.
Automatically tracking the motion of flies
We film free flying insects using three high-speed cameras. One of the main bottlenecks in analyzing these data is to accurately extract the motion of the insect's body and wings. To this end, we developed a model-based algorithm for tracking the motion of free-flying fruit flies. This method is based on fitting a 3D model of the fly, which includes the fly's body and wings, to the images taken by the fast cameras. The movie shows the fitted model superimposed on the raw movies.
Mid-Air Perturbations Reveals Roll Control
To study insect flight control we use the common fruit fly Drosophila melanogaster and a set of fast cameras that film the flies during free flight. We glue a tiny magnet to the back of each fly and use magnetic pulses to exert perturbation torques that rotate the flies in mid-air. By extracting the motion of the body and wings we aim to reverse-engineer the control-laws of the fly.
This movie shows a fruit fly recovers from a left-roll perturbation of 60 degrees. The magnetic perturbation pulse was one wing-beat long (5 ms, red line), and the fly started to respond within 5 ms from the pulse onset. The entire correction maneuver ended after 8 wing-beats.
Body Pitch Conrol
Changing the orientation of the magnet on the fly's back allows us to exert perturbation torques along different axes. This movie shows a fly recovering from a pitch-up perturbation.
Our method allows us to exert a wide range of perturbations and probe the flight envelope of the fly. This movie shows a perturbation where the fly was rolled over 8 times. During the perturbation the fly could not withstand the magnetic torque. but once the perturbation had ended, the fly went back in control within 4 wing beats. We haven't yet managed to make a fly dizzy.
Mimicry through motion:
ant-mimicry by a jumping spider
We discovered how the motion of an ant-mimicking spider makes it look like an ant to protect it from potential predators. Protective mimicry is a widespread phenomenon, in which a palatable species avoids predation by being mistaken for another, unpalatable species, called ‘model’. As such, protective mimicry is a striking example of adaptive evolution. Most studies on protective mimicry have focused on static traits, such as color and shape, rather than on dynamic traits like motion. Within terrestrial mimicry, mimicry of ants is among the most common, with spiders representing a large fraction of ant-mimicking species.
We used high-speed cameras and behavioral experiments to investigate the role of locomotor behavior in mimicry by the ant-mimicking jumping spider Myrmarachne formicaria. Contrary to previous suggestions, we found that mimics walk using all eight legs, raising their forelegs like ant antennae only for short stationary bouts. Strikingly, mimics exhibit winding trajectories that resemble the winding patterns of ants specifically engaged in pheromone-trail following, although mimics walked on chemically inert surfaces. Finally, we used behavioral experiments to show that a potential predator is, indeed, 'fooled' by the ant-like motion of the mimics.