One By One.(The Talk of the Town)(ants in city parks )

If people, viewed from a great height, look like ants, do ants, viewed at close range, look like people? Of course not. Ants have six legs, compound eyes, no lungs, and impossibly narrow waists, and they tend to hang around with aphids and mealybugs. Still, behavioral similarities make them excellent analogues. Ants, like humans, are into career specialization, livestock herding, engineering, climate control, in-flight sex, and war; for them, as for us, free will may or may not be an illusion. As for whether ants look to humans for insight into themselves, science has no answer.

A few years ago, Marko Pecarevic, a Croatian graduate student studying conservation biology at Columbia University, met with his adviser, the urban ecologist James Danoff-Burg, to come up with a subject for his master's thesis. Danoff-Burg had some data on ants in city parks and wondered if Pecarevic wanted to work on that. Pecarevic thought not. But afterward, crossing Broadway, he saw ants crawling around a garbage bin on one of the avenue's medians. Medians! As habitats, the planted medians of Broadway were ubiquitous but overlooked, suitably biodiverse but extraordinarily distressed. For someone interested, as Pecarevic was, in the ecology of heavily compromised urban environments, medians were like remote, unexplored island chains--a Galapagos in Manhattan. He decided to be their Darwin. Employing Google Earth (forgive him, he's from Zagreb), he chose three median-rich stretches--Park Avenue, the West Side Highway, and Broadway--then made himself an official-looking ID, dressed in parkish green, and started collecting ants, travelling the city with a duffelbag of garden tools and Evian bottles filled with antifreeze. No one bothered him.

On a recent afternoon, Pecarevic, a trim, wry thirty-two-year-old, went out on a survey of his medians. For demonstration purposes, he had cadged a plastic cup from a coffeeshop, and pocketed a spoon. He carried, as he always does, an aspirator, a plastic tube that he uses to collect ants. He inhales them, alive, into a chamber. "Sometimes, when you suck up ants, they're not happy about it," he said. "If you blow cigarette smoke on them, they calm down." Really, this was a farewell tour--he was returning to Zagreb the next day, to pursue a doc-torate. His thesis ("Ant Diversity and Abundance Increase with Increasing Plant Complexity and Amount of Garbage Bins in New York City Street Medians") was done, and he was bequeathing to New York some interesting conclusions about its ants.

For example, ants seem to have an astute sense of neighborhood stereotypes. The Upper West Side, as it happens, is more diverse, ant-wise, than the Upper East Side. Diversity is a function of habitat, and habitat, on the medians, is reflective of the people who live around them. As you might expect, Park Avenue medians contain fewer gar-bage cans (the greatest determinants of ant variety and abundance) and less complex flora; they are more ...