Scientists at the University of Washington (UW) have come up with an unusual way to help farmers get information about the plants in their fields. 

Farmers already use drones (无人机) to collect information about their crops. But they can only fly for 10 to 20 minutes, and can only travel for a few miles. Last year, the team at UW showed off "RoboFly", a tiny robot that weighed as much as a toothpick and could fly. But it can't fly far at all and it needs a laser (激光) for power. So the scientists began to think about things that already knew how to fly, which led them to the bumblebees (大黄蜂) that fly all day. Compared to many flying insects, bumblebees are so large and strong as to fly carrying almost as much as their own weight.

The UW scientists created a special device with sensors, a small battery, and a way of storing tiny amounts of information. This "backpack" weighs about as much as seven grains of dry rice.

To track the bee, the scientists send radio signals from several spots along the edges of the field where the bee is. The tiny computer on the bee's back uses the strength of the signals to figure out where it is. The backpack records information about the temperature and light. When the bee return s home at the end of the day, a device can wirelessly download the information the bee has collected. Another device can wirelessly recharge the backpack's battery.

In the UW experiment, the scientists cooled the bumblebees down so that they stopped moving, and then glued the backpacks onto the bees. But it would be difficult for farmers to do the same thing for hundreds of bumblebees. Besides, bumblebees don't live long — about a month. Farmers would need to be careful as the bees got older, otherwise the trackers could die while they are out in the field, leaving the electronic litter behind.