Caterpillars aren’t the most appetizing meal for humans, but for the people of Vietnam’s Central Highlands, they are the main ingredient of a regional stir-fried dish.

Every year, in the months of March and April, cassia trees in the central highlands of Vietnam are invaded by an army of yellowish caterpillars that love nothing more than to feed on their leaves. Once fully developed, the larvae leave the tree tops and crawl down the leaves to form cocoons, before turning into butterflies and flying away. But before this final transformation occurs, cassia caterpillar gatherers pick the caterpillars and pupae one by one to use in a simple stir-fried dish that can be a little hard to stomach.