The army ants were traveling through the Costa Rican rainforest. After the sun set, they would interlock their bodies to build a new nest to house the queen and larvae. The ants formed a scaffold of vertical chains by interlocking the claws on their feet.
The shape of these living nests depend on the ants' surroundings. One night, the colony assembled in the open, against a fallen branch and two large leaves that were evenly spaced and of similar height.
The resulting nest spanned 20 inches and resembled "a living cathedral with three naves," Kronauer said.