REMOTE-CONTROLLED insects may sound like the stuff of science fiction, but they have already been under development for some time now. In 2006, for example, the Defense Advanced Research Projects Agency (DARPA, the Pentagon's research and development branch) launched the Hybrid Insect Micro-Electro-Mechanical Systems program, whose ultimate aim is to turn insects into unmanned aerial vehicles.

Such projects provide proof of principle, but have met with limited success. Until now, that is. In the open access journal Frontiers in Integrative Neuroscience, a team of electrical engineers led by Hirotaka Sato of the University of California, Berkeley, report the development of an implantable radio-controlled neural stimulating device, with which they demonstrate, for the very first time, the accurate control of flight in freely flying insects.

The miniaturized system developed by Sato and his colleagues is mounted onto the pronotum (the dorsal, or upper, plate of the exoskeleton), and consists of electrodes implanted into the brain and wing muscles. Flight commands to start and stop flight and control the insect's elevation and turning were generated on a personal computer running specialized software, and transmitted to a microcontroller which is equipped with a radio transceiver and powered by a microbattery.

The device is much simpler to program and use than similar ones developed previously, because it makes implicit use of the beetle's own flight control capabilities. The researchers found that flight could be initiated by simply applying a single pulse of electrical stimulation via the electrodes implanted into the left and right optic lobes. A single pulse from the same electrodes was also sufficient to stop the wing beats. Exactly how this occurs is unclear; it is known that visual inputs can initiate flight in locusts and fruit flies, and the researchers speculate that stimulation of the optic lobe activates large diameter "giant fibre" motor neurons which project from the brain to the wing muscles.



Once initiated, flight continued in the absence of further stimulation. The beetle powers its own flight, and levels with the horizon on its own, so that the neural and muscle stimulators are only used when a change in orientation or elevation is required. Turning could be initiated by asymmetrical stimulation of the muscles at the base of the wings, with a left turn being triggered by an electrical pulse to the right flight muscle, and vice versa. The stimulator could also be used to modulate the frequency of wing oscillations, which caused changes in altitude.

Electrically-controllable insects have obvious military applications. They could be used as micro air vehicles for reconnaissence missions, or as couriers which deliver small packages to locations that are not easily accessible to humans or terrestrial robots. The beetles used here (Mecynorrhina torquata) are among the largest of all insect species, and are capable of carrying addditional loads of up to 30% of their 8g body weight. But they could also be very useful to researchers who study insect mating behaviour, the foraging behaviour of insect predators, and flight dynamics and energetics.

Sato, H., et al (2009). Remote Radio Control of Insect Flight. Front. Integr. Neurosci. 3 (24). DOI: 10.3389/neuro.07.024.2009.