We did something similar back in the late 90s. One of our students stumbled on it using a Dremel tool to make a notch in a frame for a temperature probe. We were going to name it after him - the Lenny Principle. But a bit of digging brought up references to people dragging a finger-nail over a surface (like on a chalkboard) to get the response.
It's frequency related, and we could freeze bees on up to 5 frames, hold them frozen for up to two minutes. Like Jim, we induced it both by vibration of the frame(s) and by airborne sounds. We used a frequency analyzer and a sound generator, and we had the same thought about its uses as an alternative to a smoker; and we discovered the same logistical problem. Still, we had fun using it as a parlor trick with our 5-Frame Observation hive.
What always amazed me was how fast they all froze and how many bees froze - it was like throwing a switch.
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