Good question!
Answer was found quite soon:
http://www.physorg.com/news8616.htmlBeing relatively large insects, bees would be expected to beat their wings rather slowly, and to sweep them across the same wide arc as other flying bugs (whose wings cover nearly half a circle). They do neither. Their wings beat over a short arc of about 90 degrees, but ridiculously fast, at
around 230 beats per second. Fruit flies, in comparison, are 80 times smaller than honeybees, but flap their wings only 200 times a second
When bees want to generate more power--for example, when they are carting around a load of nectar or pollen--they increase the arc of their wing strokes, but keep flapping at the same rate. That is also odd, Dickinson says, because "it would be much more aerodynamically efficient if they regulated not how far they flap their wings but how fast "
Another sources give about same figures 190 - 250 beat/s.
http://hypertextbook.com/facts/1999/MichelleFinnegan.shtml
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