It's interesting that given the collective problem solving skills of ants, that they are apparently unable to figure out not to fall into a hole.
I wonder if they just fall through by random chance, or if there was some ant at some point that left a "hey guys, there's food down here" pheromone trail, and all the ants that came after just reinforced it into an ant super-highway. If no one ever comes back to say "actually, there isn't any food down there, just an inescapable pit", then I guess ant logic says there must still be something good down there.
The memory of most ant species only lasts about 1 day. So for the group memory of the hole to persist there would have to be some sort of pattern of ants going to the hole and not going in, or some sort of warning sent near the hole. Otherwise there isn't an obvious way for this memory to persist in the colony.
Otherwise group memory can persist for years or decades to things such as the location of food sources. Which I learned in the wonderful book: "Ant Encounters: Interaction Networks and Colony Behavior"
If everyone who falls down into the hole is never heard from again, would they even be conscious of the hole?
My understanding of ants is limited, but as far as I know most of their communication is scent or contact-based, neither of which could provide communication past that first step. As far as they're concerned, it's effectively a black hole...
There are a bunch of really intelligent looking behaviors from insects, but they seem to have a common theme of "storing" information in the environment. There is a hornet that will sweep and search its nest when it brings food back, but first it will place the food down. If you move the food while the search is going on, it will do the whole search over again when it goes out searching for food. The intelligent behavior seems to be tightly coupled with the environment. Maybe the hole is enough to break some assumptions with the ants.
Sometimes, before I had my own place, I'd get home after work and run into a flatmate in the kitchen. We'd chat for a while, I'd go to my room, and the next day I'd forget my keys and/or wallet, because my 'get home and put keys and wallet in the usual place' script got interrupted.
I wonder if they just fall through by random chance, or if there was some ant at some point that left a "hey guys, there's food down here" pheromone trail, and all the ants that came after just reinforced it into an ant super-highway. If no one ever comes back to say "actually, there isn't any food down there, just an inescapable pit", then I guess ant logic says there must still be something good down there.