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of two guards to aid the “hero twins,” Hunahpú and Xbalanqué. It is a description of caching, in which workers deposit fragments where others have been left, a kind of positive feedback that leads to consolidated piles like those in the flower-filled gourds.44 Sometimes leafcutters leave their pile until the next day, though there’s a danger a competitor will steal it in the interim. The delay may reflect a preference for wilted foliage, which loses its chemical defenses, is lighter, and, like aged restaurant beef, is easier to chew.45 Caching is also efficient because the fragments are more likely to be transported onward when they are part of a clump than when they are abandoned in isolation.46

Caches of up to a thousand pieces accumulate when ants cut foliage faster than it can be processed or when the carriers’ progress has snarled. Workers might try for a time to enter a cramped nest entrance with their leaves, then give up and add their fragments to a stash outside. Or a worker on a subordinate traffic artery may drop her leaf when she reaches the main trunk trail, perhaps because, like a nest entrance, this juncture is a bottleneck, leading to traffic pileups at trail intersections. It’s also a sensible place for a cache because the ant carrying the leaf is likely to be familiar with the neighborhood where she found it and, once she’s deposited her burden, can return to cut again. If she continued to the nest, it would be hours before she made it back to that tree. By then, her knowledge of the local foraging situation would be long out of date.47

While leafcutters lack group transport teams, caching is an example of a different method of coordinating a workforce, one they excel at, called task partitioning: the subdivision of a job, such as the carrying and processing of leaves, into sequential stages. Task partitioning isn’t always effective. When I renewed my driver’s license at the DMV, I spent the first half hour in a line to get a number to wait in another line. But task partitioning makes sense if an overall savings in time or effort is the result. Among many kinds of ants, for example, it’s common for workers to take burdens directly from clumsy carriers. In leafcutters, handoffs from worker to worker often lead to a better match between leaf size and worker size. (I suspect this is because it takes a worker larger and stronger than a leaf’s carrier to get the clumsy ant to release her grasp.) The result of these transfers is speedier delivery.48 Some corporations have become similarly proficient at this kind of task partitioning, avoiding logjams by setting rules that mandate that employees who move faster in one step of a complex procedure take over from colleagues slower at that step.49 By contrast, an ant taking a leaf from a cache will likely move slower than the one who dropped it there because it is not easy for her to select a burden appropriate for her size from the pile.50 But despite this seeming inferiority to handoffs, caches are still common. The difference in local and large-scale efficiency between direct handoffs and transfers at caches reflects the traffic problems these techniques solve: a handoff is an immediate response of one worker to the difficulties of another (perhaps after she picked up a too-big leaf at a cache), whereas most caches are stopgap solutions to wholesale gridlock in the processing line.

Caches aren’t the only way ant colonies trade individual effort for a society-wide increase in efficiency. I once witnessed a remarkable sight deep in a rainforest near Manaus, Brazil: a rain of confetti spinning through the air beneath a tree. Peering overhead, I couldn’t make out where it was coming from, but I did see a column of leafcutters climbing the trunk. They were apparently delivering their harvest to workers on the ground via airmail. Many of the pieces were larger than an ant could carry and so plummeted straight down, minimizing the loss that would have occurred if the pieces had been small and light and liable to drift over a wide region. As it was, the contingent on