Queen ant's hatchery is a cave system that can be accessed from Marigold Station.
The ants here are mutated fire ants, created by Doctor Lesko in a failed attempt at reducing their size. You will be sent here during the quest "Those!".
On Doc Lesco's desk/table can be found a filtration/containment unit, within which can be found a sample of his own mutated strain of the FEV virus.
The hatchery is entered through a depression in Marigold Station's Blue Line. A large portion of the cave is a winding trail that descends further into the ground. Five fire ant nest guardians are along the route. At the bottom of the trail, the cave opens up into a large chamber with the Marigold ant queen. The chamber also contains a terminal with the capability to destroy the fire ants in the Grayditch area. A small portion of the trail continues around behind the large chamber allowing the player to see the chamber safely from behind a rock column.