Granary

A granary is a chamber where harvester ants keep their stored seeds. Species like Messor barbarus spend their days collecting seeds and bringing them home, so they always have food ready when foraging is impossible.

Granaries are drier than the rest of the nest, and that's no accident. Seeds stored in a humid chamber would start to germinate or grow mold, so the ants keep them where the air is dry. The brood, on the other hand, needs moisture. That's why a healthy Messor nest has a humidity gradient: humid chambers for the queen and the brood, dry chambers for the seeds.

In my Messor barbarus colonies, you can see the workers sorting seeds into piles in specific chambers, while the majors use their big heads and mandibles to crack them open. The broken seeds are then processed and shared with the rest of the colony.

In practice

• Choose a nest with both humid and dry areas. For granaries, I aim for very low moisture, ideally between 10% and 40%.
• Hydrate the nest from one side only, so the ants can pick the driest chambers for their seeds.
• Offer a mix of seeds in the outworld, and remove any that sprout or go moldy.