In the Rudyard Kipling poem The Bee-Boy's Song there is a section that goes:
Tell 'em coming in an' out, Where the Fanners fan,
What are these fanners that the bees are so curious to know about?
Kipling's animal fable "The Mother Hive" (1908) includes these passages:
The old Queen cried the Swarming Cry, which to a bee of good blood should be what the trumpet was to Job’s war-horse. In spite of her immense age (three, years), it rang between the canon-like frames as a pibroch rings in a mountain pass; the fanners changed their note, and repeated it up in every gallery; and the broad-winged drones, burly and eager, ended it on one nerve-thrilling outbreak of bugles: “La Reine le veult! Swarm! Swar-rm! Swar-r-rm!”
Sacharissa had run to what was left of the fertile brood-comb. “Down and out!” she called across the brown breadth of it. “Nurses, guards, fanners, sweepers—out! Never mind the babies. They’re better dead.—Out, before the Light and the Hot Smoke!”
It's clear from this story that Kipling understood fanners to be a caste of worker bees.
My guess would be that this is about bees fanning their wings at the hive entrance to cool parts of the hive. The place where the bees come in and out of the hive is exactly where they do this.
OED fanner, n gives definition 1.a. obs.
One who winnows [separates wheat from chaff using air] grain with a fan.
This seems more relevant than the other definition "one who fans". Winnowing does not seem particularly relevant to the poem as a whole, but the agrarian context does fit a poem about bees.