How and why do queen bees sing?

We all know that Insects communicate. Locusts, grasshoppers, cicada and cricket songs can fill the air of our summer nights. For them it’s mostly a matter of courtship, defence of their territory or even alarm call. And thanks to Karl Von Frich, who won the Nobel Price in 1973, we know how bees communicate. Worker bees don’t talk, they don’t sing, they dance, like in a Broadway show. Only queens “sing”. They vibrate their abdominal segments to produce a song blowing air through spiracles (little holes in the cuticle), We, human beings, can hear it because we have ears but the bees don’t, so…

How is it relevant that queens sing to other bees?

Bees, queens and workers can understand vibrations transmitted to the wax comb through captors on their legs. Now that we know how they can make the sound and how they can perceive it, the question is:
Why do they sing?
We don’t know for sure, but researchers and beekeepers have noticed that virgin and mated queens sing. Virgin queens sing when they are nearly ready to emerge from queen cells. Workers around do not care about it at all. But other virgin queens inside their royal cells respond. Researchers tried to make queens sing and they found out that olfactory stimuli such as putting a queen in a cage where another has been, or approaching fingers which have held a queen leads them to sing. Researchers discovered also that queens that have grown in twin cells have the same smell and don’t sing when they are put close together contrary to “alien” queens.