Bored of the Flies

Thad has an idea that will stop the flies, once and for all

Thad Grogan had always treated the kitchen as a workshop first and a place to eat second. One humid afternoon, he stood over the open trash can, watching a cloud of flies loop and dart above the bag. Their wings made a thin, restless buzz that rose and fell as they changed direction. The sound was small, but it filled the space between the counter and the ceiling. Thad listened longer than most people would. He began to hear patterns in the pitch and the pauses.

That night he sketched a plan on the back of a grocery receipt. A pair of cheap microphones would sit on opposite sides of the can and pick up the wingbeat frequencies. A small computer would track the changing Doppler shifts and estimate each insect’s position and heading in real time. Four compact laser diodes, one in each corner of the room, would receive those coordinates and swing their beams to a single point in the air. The beams would meet on the fly just as it passed over the open mouth of the can. The insect would drop straight down.

He spent two weekends building it. The microphones went into 3D-printed housings lined with foam. The lasers sat on quiet servo mounts he had salvaged from old security cameras. He wrote the tracking code himself, testing it first with a handful of paper airplanes flicked across the kitchen. When the code could predict their arcs well enough, he switched to live targets.

The first evening the system ran, Thad sat at the table and watched. A fly entered the zone above the can. The speakers in his laptop gave a soft click as the microphones locked on. Four thin red lines appeared, slid across the walls, and crossed in midair. The fly folded and fell into the bag with a faint tap. Another followed thirty seconds later. Then another. By midnight the air above the trash was empty.

The next morning Thad found the can quiet. He left the lid off all day and still heard nothing. He moved the whole rig to the garage, where a compost bin drew a fresh crowd. The same sequence played out. Microphones, servos, four converging beams, a short drop. Within two days, the garage was silent too.

Thad packed the microphones, the computer, and the four laser mounts into a single crate. He drove to the city dump on the edge of town, set the crate on a concrete pad near the open pits, and powered everything up. The flies arrived in numbers he had never seen in his kitchen. The system tracked them, crossed the beams, and dropped them one after another into a wide plastic drum he had brought for the purpose. He sat on the crate and watched the drum fill while the air around him gradually cleared.

When the last stray insect vanished from the sensors, Thad closed the lid on the drum, loaded the crate back into his truck, and started looking for the next place that still had flies.