The ultimate cog life

kw: book reviews, nonfiction, natural history, social insects

Humans are social animals, but we limit our sociality, and fear overdoing it. Dystopian scenarios sometimes postulate the human race reduced to a hive-like existence; we may speak of being "worker bees", particularly those with assembly-line jobs; people angrily protest against being treated as "cogs" in some huge machine (think of the old film Metropolis). We put a face on these fears with the image of the bee hive, with thousands of workers serving an all-powerful Queen:


For a real queen bee, the reality is somewhat different. She is a slave as much as the others, condemned to lay tens of thousands of eggs over a life span of a few years. I hope egg-laying is pleasurable! Whether it is or not, she must lay an egg every few minutes, a few hundred daily.

Reading The Superorganism: The Beauty, Elegance, and Strangeness of Insect Societies, by Bert Hölldobler and E. O. Wilson, I found that a queen bee is a piker. The ant queens of certain species of leaf-cutter (fungus-growing) ants lay an egg about every three seconds. That is ten million eggs yearly, almost a million eggs per month.

By the way, if you saw The Lion King (and who didn't), you may recall an early scene showing leaf-cutter ants walking on a limb, then a refocus to gnus running across the African savanna. Oops! There are no leaf-cutter ants in Africa; they are all to be found in the Americas, from southern New Jersey in the U.S. to about midway down Argentina.


This National Geographic photo (from their animals pages), shows a typical species, possibly of Atta, the type genus of leaf-cutters. It is following a chemical trail, and we typically see all kinds of ants following such trails. By adopting agriculture and having incredibly fecund queens, ants of Atta and related genera produce huge colonies with millions of members, and "anthills" the size of a house, underlain by a tunnel system that required the removal of several tons of soil. These colonies typify what Hölldobler and Wilson mean by "superorganism."

Another characteristic of the larger, more complex ant colonies is several sizes of workers. These supermajor (or supersoldier) workers, next to minors, their "little sisters", are members of a Pheidole species. The mass difference can be 200:1. In many species there are also one or two intermediate-sized "medial" worker types. Ant species with smaller colonies tend not to have more than one size of worker.

These points together comprise the characteristics of those social insects the authors call Superorganisms: a special reproductive caste, large numbers (dozens to millions) of individuals working together with considerable levels of cooperation, and communication methods for holding a colony together.

There are a very few species other than insects that have similar social systems, most notably naked mole rats, but the book concentrates on bees and ants, with just a nod to wasps. All these insects are members of the Hymenoptera (meaning "membrane winged"), but practice sociality at different levels: a few wasps are social (hundreds of species out of more than 200,000); many or most bees (30-40,000 species total) are social; and all ants (20-30,000 species total) are social.

The book takes up nearly a hundred topics in ten chapters, so I'll barely scratch the surface. Many topics are investigated with evolution in mind. For example, a line of weaver ants will pull leaves together, sometimes forming living chains to reach across a gap. When the leaves are near contact, other ants bring larvae and move them back and forth like shuttles as they emit silk to hold the leaves together. The evolutionary underpinnings of such a complex event are no simple matter to understand, and I don't claim to have grasped the point; I do understand that it is emergent behavior arising from simpler actions that are a part of other, ordinary ant behavior patterns. In fact, most aspects of social insects' collective behavior is emergent, in which each worker, operating by simple rules, does a part of a larger whole that has no particular architect.

This is particularly evident in the way swarming bees choose a new nest. Scouts from the swarm investigate various sites, and each returning scout performs a waggle dance upon the surface of the hanging swarm. The better the site they are advertising (size, location, orientation, security), the more energetic the dance, and the longer a bee will dance. Those who don't dance very long wander about, and may choose to co-dance with some who seem to have come from a better site. Such bees may go there and return, to dance more. Within a short while, often less than an hour, a large number are promoting the best site, a collective decision is made, and the swarm takes off for the chosen site. Considering bees as analogous to single neurons, this is possibly how you and I make decisions inside our own heads, when we have several options.

Ants also need to find, or dig, homes. Many species with smaller colonies, and smaller needs, can decamp routinely. Others need more elaborate accomodations. But have you ever wondered what lies beneath that anthill in your yard?

Compared to the massive nests of leaf-cutter ants, this is a cast from a relatively modest nest: the anthill was about half a meter across, and low. Walter Tchinkel, who stands 178 cm (5'-10"), studies ant nests by pouring thin cement down all the holes of a hill, then excavating the hardened concrete a few days later. The species producing this nest was Pogonomyrmex badius, the Eastern Harvester ant. You'd be unlikely to tolerate a nest of these in your lawn!

But even the little (hand-width) hills we often see can have rather extensive burrows, often going down a meter or more. It is in the construction of such nests that we see how an ant colony is really more like a single organism, a superorganism.