ANTS AT WORK
By Deborah Gordon
Free Press. 182 pp. $25
On Cowbirds, Kudzu, Hornworms,
and Other Scourges
By Janet Lembke
Lyons. 216 pp. $25
Reviewed by Susan Okie
Ant society has engrossed human observers at least since Biblical times. The central mystery is well stated in the Book of Proverbs: how the ant, "having no chief, overseer or ruler, gathers her harvest in the summer . . . to feed the ants in the winter. . . ." In a colony of thousands, who live (except for the queen) only a year, the work of food-gathering, defense, tunnel-building and housekeeping goes on smoothly in the absence of management for as long as two decades. Furthermore, the distribution of tasks constantly shifts to accommodate changes in the ant colony's environment and needs. How does it all happen?
That question has engaged Deborah Gordon, a professor of biological sciences at Stanford University, during 17 summers of research on the harvester ant colonies that dot a flat, sere piece of the Arizona desert. The plot measures only about 250 by 400 yards, but it contains some 300 colonies of these large, red, seed-collecting ants (Pogonomyrmex barbatus), which share the ground with several other ant species.
Her work requires vast stores of patience and curiosity as well as uncommon humility, a willingness to suspend one's assumptions about what makes other beings tick. "I deeply admire their harvester-ant-ness, the richness of their responses to a world so alien to me, but I am never struck by their perfection," Gordon writes. "Perhaps when I understand more about how colony behavior varies, I will be able to see why some behavior is especially likely to promote reproductive success."
Beyond their fascination as social insects, harvester ants provide a way to get at the puzzle of how complex patterns of behavior can be generated by a system in which each of the component parts seems to follow very simple rules. In that sense, a harvester ant colony is a metaphor for a human brain (composed of billions of nerve cells that have only a single, all-or-none response to stimuli) or for a developing embryo, which forms a multi-tissued organism from a ball of cells that start out identical.
Gordon wants to know how any given ant "decides" what task to do -- foraging, patrolling, nest maintenance or garbage collection -- and how thousands of individual ant decisions produce what appears to be coordinated colony behavior. To that end, she first watched, counted and mapped the movements of ants at work, then devised ways to disturb their universe. She laid down barriers on a colony's foraging trail, spread toothpicks to make extra work for the housekeepers, introduced trespassers from a foreign colony -- and then watched to see what would happen. Once an hour, she would make the rounds of each colony in the experiment to count the numbers of ants engaged in various tasks, then would spend any leftover minutes at the end of the hour reading a few pages of War and Peace. "After a few days of this regime," she writes, "I began to feel that even colonies burdened with toothpicks, barriers and cardboard cylinders all at once had a simpler life than I."
Gordon learned that ant behavior is less stereotyped than researchers once believed. For instance, ants' response to the pheromone (or communication chemical) oleic acid depends on the context: If they encounter it while foraging, they'll treat it as food, but if they detect it while doing garbage duty, they'll dispose of it as a dead ant. Similarly, worker ants don't belong to rigid castes assigned to one job all their lives; they will switch tasks or take a break in response to environmental cues, some of which they pick up when they meet one another and touch antennae.
Like all good scientific research, Gordon's discoveries spin off new questions rather than yielding a story with a neat ending. Alas, neither she nor the reader will ever truly know how it feels to be a harvester ant: You can sense her disappointment when she peers into an underground colony through a flexible fiber-optic microscope and finds that she can't thread the instrument farther than the first two tunnel branches.
But in a prose that combines detached clarity and wry wit, she wonderfully conveys the appeal of ant-ness. A couple of days after I began reading Ants at Work, I was digging up a weedy patch of garden and found that I had unwittingly exposed the top level of an ant colony. Red-and-black workers scuttled to and fro, seizing pale brown pupae in their mandibles and carrying them off to safety in the colony's deeper tunnels. Thanks to Gordon, I was able to see and admire what they were doing instead of blindly attending to the perennials.
In contrast to Gordon's loving closeup of a single species, the essays in Janet Lembke's Despicable Species offer nicely composed but less detailed snapshots of a collection of much-maligned life forms. Lembke is a translator of Greek and Latin classics and a lover of nature, especially of the birds, animals, plants and fungi that live near her two Southern homes -- in Staunton, Va. and on the banks of North Carolina's Lower Neuse River. Her natural history writing emphasizes the history, not the science. She's a keen observer and does a terrific job of explaining how creatures got their names and how they have inspired writers, musicians and explorers, but often she devotes less attention to what is known about their biology.
Lembke's focus is on ecology, including the many kinds of relationships that can exist between living things that share the same habitat, and her main point is that even the species we hate -- biting flies, starlings, kudzu -- are admirably adapted to their particular lifestyles. To my mind, her most successful essays are the ones that draw on science as well as history, culture and observation to make that point. Her chapter on kudzu is a tour de force, packed with facts about this astonishing Asian vine, which grows a foot a day and which in a matter of decades has overrun much of the South. She explains how climate and pests keep kudzu within bounds in its native Japan, how it was brought here in the 19th century by a well-meaning horticulturalist, and how it was promoted and planted by the Department of Agriculture during the Dust Bowl era to prevent soil erosion despite the early warnings of one of that department's scientists. In Asia, kudzu is used as a food starch, woven into grass-cloth wallpaper and even brewed into tea as a remedy for hangovers!
There are excellent essays on the opossum (a New World marsupial with wonderfully weird reproductive organs), on cowbirds (which are raised in other birds' nests, yet somehow always grow up knowing they're cowbirds), and on Pfiesteria piscicida, the fish-killing microscopic organism that has produced periodic ecological mayhem in streams along the Virginia and Carolina coasts during the 1990s. Unfortunately, among the weakest sections are those that focus on critters likely to be more familiar, such as gray squirrels, starlings and biting flies. Still, the book offers a buffet of literary, historical and biological tidbits that will enliven readers' experience with some of their nonhuman neighbors.
Susan Okie is a science writer for The Washington Post.