Bees

How do bees buzz?

The buzzing sound is heard when the bee makes the air vibrate in some way.
It used to be thought that the movement of the wings caused the sound. However the bees can buzz even when the wings are at rest. So it is probably the vibration of the muscles in the thorax causing the thorax to vibrate that makes the buzzing sound.


Source: http://www.bumblebee.org/faq.htm#buzz

Why do bees buzz?
Firstly, buzzing is of course, commonly heard when bees are simply flying, during which time, the wings are vibrating very fast. 

But bees will also buzz at other times, and the tone of the buzzing may alter. 

For example, they seem to buzz more aggressively if their nests are disturbed, or if they are disrupted during foraging. 

They will also buzz more aggressively if attacked or defending themselves from predators, or during conflict with other members of the colony, such as the queen.

If you have seen my page about bumblebee pollination you will have read that bumblebees are capable of 'buzz pollination'. Of course, bees buzz from flower to flower, but whilst foraging, for a few seconds, they tend to remain quiet.

Not so during buzz pollination. The anthers of some flowers (i.e. the parts carrying the pollen) only release their pollen if they are shaken. Bumblebees achieve this by placing the upper part of their body (thorax), close to the anthers, then vibrating their flight muscles very fast. At the same time, they make a lovely buzzing sound. Buzz pollination is especially beneficial for tomatoes and other fruits, resulting in a more abundant crop.

One particular type of high-pitched buzzing sound made by honey bees is called 'piping'. 

Piping occurs directly prior to swarming, but can also occur during the disturbance of a hive. 

There are differing views about which bees in the honey bee colony initiate the piping prior to swarming. 

Some sources state that the queen starts first (Werner, 1964). Others state that the piping begins with a small group of experienced forager bees called 'nest-site scouts', who produce a "piping-signal" that primes the workers for swarming (Rangel, 2008). 

It is also now believed that when honey bees 'waggle dance' to communicate the locations of food (flowers upon which to forage) to other members of the colony, it is not only the movements of the honey bee, but also the buzzing sounds made, that convey the whereabouts of the forage sources (Goodman 2003).


Source: http://www.buzzaboutbees.net/why-do-bees-buzz.html