In this mango orchard in Northern Thailand, weaver ants are nurtured so they can thrive and protect the harvest. The ants hunt the pests that would eat the mangoes, eliminating any need to use harmful chemical pesticides. The farmer creates strategic highways of red string to connect the weaver ants to new trees, expanding where they forage.
The weaver ant’s ability to build capacious nests from living leaves has undeniably contributed to their ecological success. The first phase in nest construction involves workers surveying potential nesting leaves by pulling on the edges with their mandibles. When a few ants have successfully bent a leaf onto itself or drawn its edge toward another, other workers nearby join the effort. The probability of a worker joining the concerted effort is dependent on the size of the group, with workers showing a higher probability of joining when group size is large. When the span between two leaves is beyond the reach of a single ant, workers form chains with their bodies by grasping one another’s petiole (waist). Multiple intricate chains working in unison are often used to ratchet together large leaves during nest construction. Once the edges of the leaves are drawn together, other workers retrieve larvae from existing nests using their mandibles. Upon reaching a seam to be joined, these workers tap the head of the clutched larvae, which causes them to excrete silk. They can only produce so much silk, so the larva will have to pupate without a cocoon. The workers then maneuver between the leaves in a highly coordinated fashion to bind them together.
And with a healthy orchard in balance, the farmer can harvest the mangoes and some of the ant eggs, a delicacy in the region.