When you chase a frisbee, you predict where the frisbee will land so that you can be there to catch it. The same thing happens when you change lanes on the highway. You make a prediction about where the car needs to go and accelerate just enough to change position without overshooting. In the animal world, this type of prediction making is literally a matter of survival. It’s how many animals catch their dinner. But how do animals do this when the prey--like the frisbee--is a moving target?
Scientists at the Howard Hughes Medical Institute wanted to study neurons in the dragonfly brain, mid-hunt. But there was a problem. "The dragonflies have to be flying," says Dr. Anthony Leonardo. "And traditionally they’ve been immobilized." To study the insects in flight, Dr. Leonardo and his team decided to outfit their little subjects with high-tech backpacks that carried the necessary circuitry.
The scientists constructed a super-thin circuit board (the size of a pinky fingernail and much thinner than a hair) with an even smaller processor to amplify the insect’s neural signals. They then performed "insect brain surgery" under a microscope, embedding wires in the dragonfly’s belly. These wires connected to the backpack, which wirelessly broadcast the signals to a computer.
Engineering the backpack wasn’t easy. Dr. Leonardo says that trying "to load an insect up with gear is like dancing in a ballet wearing a backpack filled with rocks. You can put double the dragonfly’s body weight on these creatures and they can fly, but they won’t try to catch their prey."
Eventually, they engineered a backpack that weighed 40 milligrams, so light the insect didn’t even notice he had it on. They secured the backpack to a Common Whitetail dragonfly with a small drop of superglue, and then they set it loose to chase down some scrumptious fruit flies.
The team is just starting to observe and record the insects’ neurological behavior, so they haven’t made any definitive predictions yet. Maybe once they do, they can start to explore whether superhero-themed backpacks will make the insects better hunters.
[Photos by Anthony Leonardo | Janelia Farm Research Campus | HHMI]