[whimsy]

I know how ants stop going to a food source (e.g. the pheremone trail stops getting refreshed on the return trip) but how do bees stop? I know they transmit pathfinding information with dancing... do the bees just stop dancing on return or something?

The reason I ask is the 1-5% figure you mention. I assume bees must have some mechanism to prevent sending bees to fatal sites. For ants, no one comes back, so no one keeps going. Ant traps short-circuit this by providing food with a slow-acting poison - the ants make it back with "food," causing more ants to be sent, and soon a significant portion of the stockpile is poison, drastically reducing numbers in the colony. Could that have happened here? It sounds like that's probably not the case, given that the bees appear to have died practically on contact with the linden trees.

But I don't know how bee flow control works.