So... I'm assuming it requires a unique hatchery? And looking at the size of it, and purpose, I would assume there is little to no benefit from sending them out to the surface to do what workers usually do.
If I were to take a wild guess on how they farm, I would say that they occupy a tile of fungus and work on it for a period of time. After a while, they would harvest the fungus and put in in the food storage tile.
Or, more likely, the fungus farms ARE the food storage tiles, and the workers place the insect flesh on the tiles for it to decompose, with the help of the minums. I'd assume that upgrading the fungus tiles will allow more insect flesh to decompose on that tile, making more food.
Is there a chance that fungus will be an entirely new food system in formicarium mode? Leafcutter ants only eat fungus, after all.