Assembly lines and the Simplicity of Leafcutter Societies

Bert Holldobler & Edward O. Wilson devote a concluding chapter of their 2009 the Superorganism to the leafcutter ants, for one thing "because they possess one of the most complex communication systems known in animals." As their book and mine describe, leafcutters have an elaborate assembly line for processing foliage and rearing fungus on the resulting leafy mulch as their food.

This gardening is indeed in many ways as complicated as human agriculture. But Holldobler & Wilson's assertion set me thinking. Does that necessarily mean their communication system is complicated, too? I wondered if too much communication in an assembly line could actually be counterproductive.

In my correspondence with experts on factory organization, I found that they recognized the negative effects of too much chit chat between assembly line workers. Steven Watts, author of Henry Ford and the American Century, wrote me that "Ford's managers tried to set up their assembly lines in such a way as to make communication unnecessary and would speed up the line to thwart it when it appeared."

Indeed, much of the work among leafcutters appears to be based on "stigmergy:" rather than actively communicating with each other, the appropriate ants just complete the task that comes before them, as humans do on an assembly line (for example, the minor worker in the image below has taken a batch of fungus that needs planting--with no communication required). My prediction then is leafcutter ants employ simple communications compared to what we might have guessed from the complexity of their social operations. Leafcutter communications may be no more complex than a variety of other ants with similar colony sizes; it's just that we have studied leafcutter ants in much greater detail than most other ant species.

That doesn't mean that their communications are simple: Adventures Among Ants describes a number of means by which the workers are known to transmit information to each other; and their fungus also appears to convey its needs to the workers as well.

What ants have the most complex communication system? Not the army ants, which have been able to strip down the complexity of their communications through a loss of autonomy which keeps the workers in constant close contact. I agree with Bert Holldobler & Edward O. Wilson's conclusion in their book The Ants, that the Oecophylla longinoda weaver ant, which these authors have shown employs five recruitment systems, is a clear winner.

But like humans, with their even more complex communications, this fact doesn't convince me that weaver ant colonies superorganisms nonpareil. (Similarly not all organisms need complex internal communications.) In terms of social integration into a cohesive whole, nothing matches mass hunting species such as the army ants.

This essay expands upon the discussion on page 174 of AAA.