Bumble Bee

Dear reader
( hopefully someone will read this, and if not, there is nothing to do about it)

My family is getting bigger and bigger. Not that I am continuously  involved in reproduction matters but sometimes the new family members just show up and they stay (for example our Louise).  Now we have a couple of bumble bees as a new arrivals.
Bumble Bees came one spring day to our garden and they occupy the empty nesting birdhouse now  I made last year for a pair of Blue Tit. (This year, however, the house stood for rent but luckily not too long!)
I guess after some interior adjustments Bumble Bees founded their own nest.  I am really very curious what is going on inside of the nesting house. The small opening is to narrow  for my eye and I do prefer not having my eye to be punctured by bumblebee's stinger. So I have only very hazy idea about their activity.

BUT I can hear them.  And I can hear them very well. It is  pretty hot last days and the temperature rises in their house rapidly in the afternoon because their house is than fully exposed to the sun rays. The nice and concerned bumble bee is sitting in the entrance of  the (former) birdhouse moving rapidly with his wings, cooling down the bumble bee babies inside.  I noticed , when one is tired of fanning the other bee come and take it over. Thermoregulation is very critical for bees. It is just amazing how they can substitute  sophisticated air-co by something like a pair of wings  powered by their wing muscles. (but not very silent!)
I was getting mad from the buzzing and I made it easier for them (and for me as well) : I put a small piece of wet cloth on the roof of their house and the "buzzing" period  was significantly shortened ! Now  I consider to register my invention as a patent  by WTO.

I enclose a shot video  to get an impression. You hear not only buzzing sounds but also  screaming for help.
Translated with Google Translator, from Bumblish to English:

Help, it's damn hot here!