High speed video of Bombus sound production

The video shows the animal immobilised as described in the methods for the acoustic recording. There are two distinct phases of sound production: (i) 0:01 – 0:26 the insect flies in a characteristic manner with high amplitude wing strokes that produce a waveform similar to that seen in Figure S2A; (ii) 0:32 – 1:03 the insect responds to the simulated predation by transitioning to the alarm sound with nearly static wings and bodily contractions. It is suggested that this involves the decoupling of wings from the flight muscles similar to the mechanism of wing whirring that is used as a thermoregulatory mechanism in this species.