The buzz foraging vibrations of Bombus terrestris and B. hortorum workers, measured byan accelerometer attached to the flower stem, reached relatively high acceleration magnitudes of 212 m/s2 at frequencies of 374Hz. B. hortorum workers were more effective than B. terrestris workers at vibrating the anthers of Symphytum officinale (comfrey) because they inserted their heads into the corolla for nectar. The escape buzz produced by B. Terrestris during capture was similar to that produced during pollen foraging on Actinidia deliciosa (kiwifruit) and required 0.3 W to generate. Both species of bumble bees created the high magnitude vibrations by triggering resonance frequency vibrations in their ventral and dorsal plates (sternites and tergites). This caused amplification of a random vibration input, at the resonance frequency, by a factor of 2.3. B. terrestris workers that had not previously foraged on kiwifruit flowers showed buzz foraging, indicating that it was either an innate foraging technique, or that floral cues exist which stimulate buzzing.