During the hot days of summer, the hives are fairly roaring with industry. At midday you can hear it from five feet away: a steady, low hum, like machinery in a distant factory. (This is a sound entirely different than the high, warlike warning they make when they're irritated at us).
Our girls are busy, despite the heat, and the landing board is a mighty intersection of field bees setting out to forage or lumbering home laden with pollen and nectar. Once home, the returning bees are greeted by house bees waiting to take in the groceries. But in hot weather the bees have another job: apiary air conditioning.
Bees are tolerant of heat, preferring hive temperatures of about 92-95 degrees Fahrenheit. When the hive starts getting too hot and muggy, the bees cool it down by fanning.They increase and direct circulation in the hive by fanning their wings. It's a mystery how they know where to stand, but on hot days some bees come out on the landing board to fan, and you can watch this part of their intake and exhaust system.
As you can see in the photo above, they fan so fast that their wings disappear. The first time I saw this, I thought, oh no, what new plague has taken our bees' wings from them? Then I realized they were just flapping for all they were worth, keeping their home comfortable. The bee in the top right of the photo is coming home; the yellow lump on her leg is pollen.