What are the bees doing?

[Al]

It has been about 90 degrees the last two days. The bottom board on the outside (landing area) is covered with a single layer of bees. There are bees covering about one-third of the first super in the front. A few bees are fanning. The rest are backing up in a straight line, moving forward and backing up again. They are moving quickly too. I have two hives doing this. There is a honey flow going on now. Does anyone know what they are doing?

[Andrey]

AL,
There was a discussion on this topic not very long time a go. Here is a link:
http://www.beesource.com/ubb/Forum2/HTML/000255.html