Not just picnic pests

kw: book reviews, nonfiction, memoirs, animals, social insects, photography

Ants! They outweigh us. There is at least one of their colonies, or societies, that outnumbers the human race by a huge factor. The renowned scientist Edward O. Wilson is but one of many scientists whose career has been devoted to them. Another is his student Mark W. Moffett, who has the added distinction of producing the best-ever photographs of insects. While Adventures Among Ants: A Global Safari With a Cast of Trillions is not quite a coffee-table book, it sports numerous photographs that I would class among the best wildlife photographs ever taken.

Look at this image of the African army ant Dorylus [the species is not stated]. Sharply focused, superbly composed, with stunning lighting, it exemplifies the genre. As the author explains in his first chapter, when he set out to study ants, one of the first books he obtained was a guide to photographing models, and he particularly studied the lighting techniques. This attention to detail earned him the attention of National Geographic editors, and he has worked with them from time to time for decades.

In this book, Dr. Moffett focuses our attention on six genera of ants: The Marauder Ant Pheidologeton diversus and related species of Asia, The African Army Ant Dorylus, the Weaver Ant Oecophylla of Africa and Australiasia, and in the New World, the Amazon Ant Polyergus, the Leafcutter Ant Atta, and the Argentine Ant Linepithema humile.

Marauder ants, a moniker the author gave them, are similar to army ants, a case of convergent evolution. A marauder colony is omnivorous, taking about equal amounts of animal prey and high-quality plant matter by raiding along a broad front supported by a network of pathways and long-established trunk lines. This species has the greatest polymorphism known, with four sizes of workers, and the largest "giant majors" are up to 800 times the weight of the smallest minor workers. Imagine a small man, say 125 pounds, working with a large brontosaur weighing 50 tons (eight times the weight of the largest elephant). Can you say Fred Flintstone?

Both Marauder ants and Army ants exhibit great polymorphism and extensive division of labor. The large workers aren't just soldiers, but do all kinds of heavier tasks. A swarm of the smallest workers typically suffices to immobilize a prey insect or small vertebrate, but it often takes a visit by media or major workers to complete the killing and dismemberment of prey into carryable pieces.

What these two kinds of raiding ants are to ground-level biomes, the Weaver ants are to the treetops. They are less polymorphic, but do have a division of labor based more on the age of the ant. Though they raid like army ants, they are also ranchers, caring for scale insects and other honeydew-producing "cattle" in some of the leafy "houses" they construct using silk from their larvae.

Almost total opposites in habit are the Amazon ants, one genus of which are the familiar "red ants" of American back yards. I call them the Lazybones ants, because they don't work. Solomon certainly did not have Amazon ants in mind when he exhorted, "Look to the ant, sluggard." The only work an Amazon ant does is to raid a nearby Formica (black ant) nest to steal the pupae. A few thousand red ants at a time will go out in late afternoon and raid a Formica nest. The black ants put up little resistance besides blocking the anthill entrances. Once the red ants break in, the black ants let the raid proceed. The stolen pupae are hatched in the red ant colony and raised to be slaves, by slaves already there. The red ants don't even feed themselves, and would starve if not fed by slaves.

We're back to ants that work for themselves. Probably the hardest workers are the gardening ants, the Leafcutters, such as these Atta cephalotes workers, also called Parasol ants, carrying leaf cuttings to the nest.

In the nest, leaf pieces are chewed into mulch and added to a fungus garden, which small workers tend assiduously, cleaning out competing fungi and killing encroaching pests, except for a few species that employ chemical camouflage, which is a problem that most ant colonies encounter. These little agriculturalists have been perfecting their farming techniques for fifty million years. The relative efficiency of genetic versus cultural evolution is thus starkly shown: most of the progress they made over those millions of years was raced through by humans in about eight thousand years.

Hey! Any conspiracy theorists reading this? How's this for a global conspiracy? There is a supercolony of Argentine ants called the Very Large Colony that covers much of the state of California, and bids fair to spread nationwide. These little gray "sugar ants" (a frequent visitor to the American kitchen) number in the trillions and are the largest superorganisms known. Where the Argentine ant has invaded America, most other ant species are in decline or have been wiped out. The only ant that typically holds its own against them is the Fire ant. Get this: Fire ants also hail from Argentina.

Argentina is a breeding ground for super-ants. When a colony of any ant species from Argentina gets started in a North American (or European—watch out, you guys!) yard, it is like dropping the Phillies among the Little Leagues. Nobody else is gonna win any games. Argentine ants, in particular, are accustomed to constant warfare, are super-aggressive, and even though the workers are all quite small, they are fearless and stupendously numerous and simply swamp an enemy out of existence.

Both Argentine and Fire ants have multiple hills and multiple queens over the area dominated by one swarm. Dr. Moffett makes a good case that each swarm is a single species, so that there are four species/supercolonies known in California, and a handful around the rest of North America. They are reproductively isolated because they kill any ant that "smells wrong", including flying-in drones that might provide genetic mixing. The borders between colonies are no-mans(ants)-lands that host constant wars. If you happen to live in Escondido, for example, and live in just the wrong place, your yard is a battleground, always littered with dead ants.

In a closing chapter, the author muses on three ways of thinking about an ant society: as a society, as an organism, and as a mind. As to the latter point, though it seems a stretch, the way a group of ants milling about reach "decisions" related to food, or nesting places, or where to go, bears quite a resemblance to the way neurons in an animal brain are thought to reach decisions. Whereas the neurons in a human brain communicate over small distances at speeds of about 66 m/s (150 mph), ants communicate at their walking/running rates of about a meter per minute. Yet the number of neurons available for ant thought in a large colony easily exceed the neurons in a human brain. Like the mills of the gods, ant thinking must be very slow, but exceedingly detailed.

Just six species, of the 12,000 or more that are known! There is so much yet to learn, and one lifetime is so, so short. A book like this is the best reason for the existence of books.