Into the Fourth Dimension.

"The front of a church I had never been in had become a gaping hole, its many doors propped widely open."

"If you are ever bored or blue, stand on the street corner for half an hour," writes Maira Kalman. She does not say what she expects will happen to you, your boredom, or your blueness after a half hour, but I now feel equipped to take a stab at it. On a humid, still day in late summer, I stood with Kalman, my friend and sometime co-conspirator in celebrating the ordinary, on a number of street corners for many minutes. We even stopped and sat on a bench at the median of two intersections for a solid thirty-five minutes. Not only was any glimmer of boredom vanquished, but I'll be darned if I didn't grow less azure by the second.

Kalman is an ill.u.s.trator: her gouached, fantastical drawings are widely published-and then torn out of their magazines and newspapers and taped to office doors and walls. She is also a h.o.a.rder, in the finest sense of that word, of both experience and image. Whereas typical h.o.a.rders accrue unreasonable quant.i.ties of physical-frequently nonessential-items, Kalman restricts her collecting to the noncorporeal.1 She does not seem to favor the beautiful or the refined; nor is she only interested in the grotesque or curious. She collects the ordinary, the things that you trip over but have forgotten to look at. Her portrait of a pair of scissors has them planted jocularly (if scissors can be jocular) across a red background. They are not just any scissors, but that's the rub: they were just any scissors to begin with. What changed them, or the cakes, tape dispensers, bottles, and lunch trays she has drawn, is that Kalman has looked at them, set them just so-and made us look, too.

I suspected that the reason the street corner is such an unboring, unblue place to stand with Kalman is that a lot of ordinary happens there all at once. I asked Kalman to walk with me so that we could look avidly at the ordinary. One perceptual constraint that I knowingly labor under is the constraint that we all create for ourselves: we summarize and generalize, stop looking at particulars and start taking in scenes at a glance-all in an effort to not be overwhelmed visually when we just need to make it through the day. The artist seems to retain something of the child's visual strategy: how to look at the world before knowing (or without thinking about) the name or function of everything that catches the eye. An infant treats objects with an unprejudiced equivalence: the plastic truck is of no more intrinsic worth to the child than an empty box is, until the former is called a toy and the latter is called garbage. My son was as entranced by the ubiquitous elm seeds near our doorstep as any of the menus, mail, flyers, or trash that concern the adults. To the child, as to the artist, everything is relevant; little is unseen.

Once you look at what seems ordinary long enough, though, it often turns odd and unfamiliar, as any child repeatedly saying his own name aloud learns.2 I had the suspicion that walking with Kalman would be the ambulatory equivalent of saying my own name aloud a hundred times. An inveterate walker, Kalman was happy to wander the blocks of our shared city with me. We met just off an intersection-an auspicious start for a walk with a person who declaims about street corners.

As we began, our attention went in different directions at once. While I was beelining down the block, Kalman was loitering. The vines peeking through an ornamental gate impressed her. Overhead, she noted that the signage of the scaffolding company featured one of her repeated ill.u.s.trated motifs, the pyramids. Already, we were in familiar but odd territory. I thought of the German biologist Jakob von Uexkll, known for trying to imagine the sensory world of animals, whose approach has inspired my own research into the perspective of a dog. He observed that we are lazy in imagining the perspective of other people, too. "The best way to find out that no two human Umwelten [world-views] are the same," he wrote, "is to have yourself led through unknown territory by someone familiar with it. Your guide unerringly follows a path that you cannot see."

Following Kalman's path, I was led straight to a discarded couch on the sidewalk. She spied it and just about leapt out of her skin with excitement.

"Oh my G.o.d. That's like the bonanza of bonanza-there it is-it's a sofa on the street, I cannot believe it."

All too familiar with the twice-weekly trash piles that acc.u.mulate on city sidewalks as New Yorkers shake their houses upside down until the dregs fall out, I could believe it. The subject of Kalman's excitement was a long wooden couch set ungloriously near a mound of trash in front of an apartment building. Alfred Kazin, writing about walking in early-twentieth-century New York City, spoke of the "nude, shamed look" of furniture left outdoors as trash. I felt for the sofa: it belonged inside, partnered with stuffed armchairs and flanked by end tables, not exposed to weather and upturned dog legs. But Kalman loved it for the boldness of its naked arrival on the curb. She pulled out a small digital camera and snapped a photo, continuing to intone: "One cushion-it's extra bonanza." The single cushion beckoned the weary pa.s.serby to spare a moment to recline. One could see it had been well reclined upon in its previous life. Though the couch's edges were worn and one leg was buckled, it had the look of former elegance: clean lines, no surfeit of frilliness, a proud back. Under our gaze it seemed for a moment to turn elegant again, lightening my heart burdened with the thought that it was now simply trash, unattended by side chairs and a coffee-table manservant.

We walked along, carrying the sofa with us in Kalman's camera, where it would join her collection of photos of spent and discarded chairs and sofas.

"Once you start looking," she advised, "they are everywhere."

We had thrust ourselves off the corner. The real magic of the walk happened then, when we stopped standing there and began to actually amble. With Kalman, walking around the block entered a fourth dimension.

Of course, I-and each of my fellow walkers-had been in four dimensions all along. Still, the progression of the walks was decidedly three-dimensional: always up, down, and along sidewalks. Except when disabused of this notion by my son, I had defined each walk as a straightforward journey along a path between two points, A and B, the beginning of the walk and its end. What we manipulated was the time it took to cover that path: many of my co-walkers had slowed down to look more carefully at something underfoot or overhead. Occasionally we sped up to catch a glimpse in a store window before a shutter was pulled down, or we briefly galloped, as though someone were lighting a match to our tailcoats, to avoid becoming a pedestrian-automobile accident statistic.

But with Kalman, the definition of the s.p.a.ce changed. She walked straight off of the sidewalks. I don't mean she floated, in her blue canvas sneakers, hovering inches off the ground. (Though the image suits her, and matches many of her charismatic drawings that pose the subject, be it a pleated skirt or a robin, frameless on the page.) No, Kalman climbed not a tree. Instead, she veered. She abandoned the course. She left the route and wandered into buildings that interested her. Over the course of five blocks and two hours, we went off course a half dozen times. We knocked on the door of the local halfway house. We meandered into a church. We descended into a bas.e.m.e.nt senior center that advertised itself as being specifically for "black social workers." We made it into the anterooms of an odd small museum of Russian art and a Buddhist temple, only stymied by ongoing renovations in each. Eventually, we made it from A to B, but not before visiting all of the later letters of the alphabet.

Beyond this, she implicated others in our walk. We spoke to a mailman, various policemen, a couple of movers, numerous pa.s.sersby who Kalman for unknown reasons thought might be able to tell us the name of the man featured in a horribly done plaster bust set in a first-floor window, folks working at the halfway house and senior centers, people entering and leaving the church, people who had simply stopped in their walking (for reasons of infirmity or tourism) somewhere near where we had stopped, and an office worker and two cooks doing work behind windows open just enough for Kalman to call in to them and for them to acknowledge us.

Kalman's boldness was matched by my admitted discomfort. I try, as an accredited city resident, to manage coexistence with millions of strangers by keeping pretty much to myself on the street. I had not spoken to this many people on the street in my last hundred ventures from my house. Kalman forced me, reluctantly, to remove my invisibility cloak and read the social-workers sign as though it were really inviting us in. Her frank interest in others made me think about the feeling of privacy we carry with us from our homes into public, where there is truly no privacy. I had not noticed, until forced to by Kalman's sociability, how I was engaging in a fundamentally social activity by walking out in public.

Still, we all have a sense of the "appropriate" personal s.p.a.ce around us-a kind of zone of privacy that we wear, even on the social sidewalk. Indeed, we have many coencentric circles of personal s.p.a.ces, plural. The Swiss zoologist Heini Hediger, elaborating from studies of animal behavior, proposed that the personal zones around us fall into a few categories. Those with whom we do not mind "inescapable involvement"-as our loved ones-can broach the closest zone and get nearer than eighteen inches to us. At that proximity, we can smell them, feel the heat of their bodies, their breath, hear the small sounds they mutter or emit. We can whisper together. Most social interactions take place in a comfortable zone about one and a half to four feet away-closer in some cultures (Latin American) than others (North American). Friends can waltz through; acquaintances can hover on the edge. We have a social distance up to twelve feet from our bodies for more formal transactions, or for those we don't know well. Beyond that is a kind of public distance in which we use our "outdoor" voice. All of these zones are artificial, varying with differing relationships, based on context and the physical setting-but we have a bodily sense of the reality of these s.p.a.ces. Violate them, and we may feel stressed and anxious.

Kalman minded people's s.p.a.ces, but she seemed to see personal s.p.a.ce as an indication that there was a person in that s.p.a.ce to engage with. Of course, the persons had to be willing to be engaged with. We make judgments about people-their trustworthiness, their intelligence, their beauty-in glances that take less than a third of a second. All those quick glances aimed at Kalman and me must have added up to many seconds' worth of judgments over the duration of the walk. (Apparently, we were judged to be basically nonthreatening.) These engagements and our path-veering led, ultimately, to various curious episodes. Our first foray off course was into the halfway house. It did not identify itself as such-but its entranceway distinguished it from the austere residential buildings on either side. In the vestibule there was but one sign. Not an identifying placard-at least, not directly. "Please remove your hats on entering the building," it read.

Kalman immediately looked for an informant. She inquired of the weary, uniformed man sitting behind the window at the facility's entrance about the sign's provenance and meaning. We were clearly the first to ever so ask. He looked at us with a long, steady gaze. I looked away, but Kalman happily persisted. As they chatted, I looked around at the anteroom of the building. This s.p.a.ce was roughly seventy feet as the crow flies from my own living room; I had never been inside. The same is almost certainly the case with all of the buildings in the vicinity of your own home. Though we become accustomed to the look of our neighborhood from the street, it is but the skin that we see. Though this building looked residential, the entryway revealed its business core: Plexiglas set off the guard's post; the elevator was of the industrial varietal, and a handful of visitors stood in solemn observance of its slow travel. The room was unlovely but eye opening. We went no further. Back outside, my vision was changed: I noticed that more than a usual number of people edged the tree pit outside; cigarette b.u.t.ts by the curb now indicated to me the presence of many people forced to go outside to smoke. I imagined that every hatless pedestrian was headed into that building, probably feeling a little naked of pate.

As we left, I swung around to watch the building click from its old, familiar face to this new one, informed by what I now knew of its inside. The door settled into its jamb. Through a window I could see the guard's eyes following us. So much for being invisible. When Kalman wanted to get the guard's attention, she looked him in the eyes. Now we were the subject of his gaze. This may seem trivial: gaze and eye contact are the most simple of acts. But they sit squarely at the center of our advanced social intelligence. There is a reason we can imagine others' perspectives, have empathy, infer others' goals, communicate-and it begins with a shared gaze.

It could be a happy accident of pigmentation, this interest in each other's eyes. The sclera of our eyes lost its dark coloration somewhere on the route between chimpanzee and human. With the whites of my eyes as backdrop to my bright blue irises, the direction of my gaze suddenly becomes plainly distinct. I cannot avoid being spotted looking at you by turning to the side and sneaking a peek out of the corners of my eyes. (Not only can you see me looking, I would look sneaky.) Even worse, as our ancestors came out of the trees and onto the plains, the entire shape of both our faces and our eyes changed. Our faces flattened: while the human face allows us to smush it fully against a windowpane or to receive a coating of pie from a pie t.o.s.s.e.r, the monkey's face has a prominent snout, more like other mammals. The architecture of the human face is centered on the eyes, not the mouth or nose. Our cheekbones are conspicuously high-right below the eyes. The forehead and eyebrows complete the framing on the other side. Even the nose gets in the action, serving as an indicator of where our faces are pointing. Unlike most mammals, we have highly developed facial musculature, including around the eyes and even in the eye itself. What we lost in expressive potential when we lost tails is made up for by our ability to squint an ironic half smile-distinct from a full-bore joyous grin or a grimace. Along the way, too, the shape of our eye opening got squashed, revealing more of the whites.

What pure disappointment these evolutionary developments might have been to their first bearers. Just when they thought that their attention was private, now everyone else could read it on their faces. It could be no worse if a Magic Marker traced a circle around your genitals when you felt attracted to someone, or your forehead scrolled the text rambling through your head in private thoughts.

But our ancestors dealt with this change, and it was the harbinger of the development of the so-called social brain of present-day humans-one keen on others' faces and eyes, and on the personhood behind those features. There is no one area in the brain that organizes our social understanding; instead, it is a network of regions in the cortex and subcortex, but especially parts of prefrontal cortex, right behind our forehead. There is something lovely about how eyes, windows to the mind, are contemplated in the s.p.a.ce nearly right behind them. But they get there indirectly: the occipital cortex, processing raw data received through the eyes, is at the very back of the head.

In that extra loop through the cortices of the brain, gaze gained meaning-lots of meaning. Gaze reveals that we are attending, and we react physically to seeing someone gazing at us. The sympathetic nervous system, responsible for revving up our bodies to run when we spy that lion, and for calming us when we are sitting down digesting dinner, treats gaze as something of interest. It reacts in the way it would if we saw a lion-just more moderately (unless it is a lion's gaze). Adrenaline starts coursing through us, our heart pitter-pats, our breath subtly quickens, and we begin to sweat. How we feel about that rush of excitement depends on what we think the gaze means. And this depends on context: is it our lover gazing at us (I must really love him back) or is it that creepy guy across the subway car (I've got to get out of here)? Fear and s.e.xual attraction are in the head; the body prepares the same way for both.

In all events, the gaze is salient. We notice it, and we notice it from day one. Newborn babies can do very, very little when they first appear in this world, but they are already making one choice clearly. They prefer to look at a face looking toward them than one looking away. Later, this mutual gazing between oneself and others will be a way to convey a sense of closeness or understanding. Indeed, the easiest way to get an infant to smile is to simply let them see you looking right at them.3 From those first gazes on, we look at the ones we love, and we tend to love the ones we look at. Or those who look at us: researchers have found that in a controlled setting, we like unknown people who gaze at us more than those who do not. When we are in an audience, we are delighted by eye contact with whoever is on stage. Not only do we rate them as better speakers or performers, we think they are stronger, more competent, more attractive, and more credible.

Unless they stare. A fleeting glance can, if it is less fleeting, turn sinister. The gaze of a stranger is unwelcome. Even the gaze of an oil painting can be disconcerting. Part of the animacy of Renaissance portraits is that the eyes seem to follow you, half-flirting and half-glaring as you shyly try to duck out of its gaze. It is the cues of the face that cause us to feel this way, since they never change: if the subject's eyes are locked on the viewer's from one vantage, they will always be so locked, wherever that viewer goes.

My solution to get out of this eye lock with the building guard? Walk out of his view. A block away, though, Kalman found the senior center, another place to enter. I had pa.s.sed this place for years and never more than glanced at it. A few short stairs later and that story was changed. We walked through heavy gun-metal doors that looked too heavy to be propped open by the wooden shims at their feet. The room beyond was certainly a public s.p.a.ce-its sign and open doors indicated that-but not a beckoning one. As we entered, we took on the mode of visitors to a church: quiet observation, neither talking nor conspiratorially whispering together. Inside, there were established games of bingo underway; O47 and N4 excited a number of players to dutifully stamp the array of cards laid out in front of them. The walls were decorated with admonishments and instructions. One hand-stenciled sign told us that lunch was $1, a bargain on the west side of Manhattan. A man's onion-chopping cadence sounded like it might be a Ping-Pong game, and Kalman's face brightened at the possibility. A connection between Ping-Pong and onion-chopping was thereby forged in my brain. We watched the onion performance, were handed an "Activities calendar" by an employee, and aged fifteen years before we decided, by mutual head nod, to turn back to the street.

Approaching an intersection (a corner), we slowed, instead of hurrying, when the Don't Walk sign blinked at us ominously. Getting stopped allowed us to notice the miscellany that was hanging out at the corner all the time. I learned from my son how much happens when you are waiting for the thing that is supposed to be the big event. He never complains about waiting for the subway: simply the platform provides thrill enough, with trains screeching and zooming by, flashes of lights and rumbles underfoot, swells of people entering and exiting. Kalman slowly pa.s.sed a line-up of newspaper bins, considering each one as though they were displayed for sale at a flea market. I followed the arc of a tossed crumpled paper bag that failed to pa.s.s the lip of its target huddled by the streetlight. Together, we gazed, bemused, at a sign giving instructions for the Walk/Don't-Walk street-crossing signals for pedestrians (weren't they self-explanatory?).

The light turned, and we followed the instructions, feeling dutiful. Kalman spotted a church up ahead. At this point into walking with her I suspected what would happen next: we would be going in. Of course, this church, too, I had never visited, despite its open doors, shaded interior-so alluring from under the watch of the sun of summer-and occasional hallelujahing chorale. Once inside the church, we wandered down the middle aisle, as churches seem to allow anyone to do regardless of denomination, personality, or number of cameras around one's neck. From inside, the street was visible, but seemed suddenly distant. As we walked, our cadence slowed, and we were no longer proceeding at New York pace. We were walking leisurely, at a tourist's pace, because we had become visitors in our own city. The street signs were in a foreign language and the churches were all to be checked off on the map. After a tour down and back the aisles, we met again by the exit. Kalman spotted a wooden sign over a recessed area in the wall. POOR BOX, it read-a label at once no longer valid (there was no box) and also apt: Poor box! Gone missing from its alcove! She snapped a photograph.

Back on the street, Kalman was church-prompted into talking about her own churchgoing. This was a definite fourth-dimensional fact for me to learn about this New Yorker born in Tel Aviv. But she loved the music of the congregation at Saint Thomas Church on Fifth Avenue. And she marveled at their permissiveness in letting even a non-believer warm their benches: "You can do whatever you want-well, maybe not anything you want. But you can come and go. You can do anything and you don't have to do anything."

I was beginning to see what Kalman saw. She did not see a s.p.a.ce as defined by an edge, but as an infinitely explorable openness. The church may seem to be about religion, but for her it was about music and company and freedom of allegiances. The senior center might seem to be for seniors, defined by its name to exclude us, two nonsenior non-social workers, but its doors were open and that was all it took for Kalman to wander in. Take a left turn where you ordinarily take a right; open the gate to the block garden you have never visited; view the pa.s.serby as a person who is waiting for you to speak to him.

Kalman's movements and behavior also highlighted, however inadvertently, the multiple claims to s.p.a.ce in a city. Cities are filled with a variety of private and public s.p.a.ces, s.p.a.ces one can enter and s.p.a.ces one must be invited into. In the latter case, an open door may be the only sign that the public is invited in (but owners reserve the right to take a look at you and boot you back out). At times the dividing line is non-obvious, but most urban residents instinctively mind these boundaries and do not cross into private s.p.a.ce. City sidewalks present a great confusion of private and public: they are generally public s.p.a.ce, which means they are owned by the city-which in turn means that anyone who wants to plant his stake on the sidewalk must pay the city and get a permit. With munic.i.p.al permission, a restaurant, under private ownership, can take over a portion of the sidewalk for outdoor seating. The newspaper stands pay for the right to appear on the sidewalk, as do food carts and other vendors. Should you just want to walk and speak loudly, declaring your protest of this or that, or should you want to display art or be art on a public sidewalk, you need a permit. But sidewalks are also the responsibility of the ab.u.t.ting building's owner. These owners must repair, clean, shovel, and generally maintain the sidewalks in front of their buildings-but they are not "theirs."

Urban buildings, by contrast, are generally private s.p.a.ces, often owned by one party (a landlord or corporation) and leased by another (a tenant). In buildings owned by cooperatives, the corporation owns all the s.p.a.ce up to the rooms themselves, including the interior of the walls. In New York City, there are also "privately owned public s.p.a.ces," which developers create and maintain in exchange for the right to build taller buildings.

What struck me about Kalman was that she moved through all the s.p.a.ces with ease. Had she opened a mailbox on the street (federal s.p.a.ce) and lifted out a letter, I would not have been surprised. Sure, she didn't climb any walls, but her ability to transcend the social and cultural knowledge of where one is allowed to go felt like a superpower.

Is there something about Kalman's brain that leads her to see more possibilities on the street than I do? Simply put, yes. Neuroscientists are just beginning to put together a picture of what exactly it might be. The difference is not simple, nor is there a canonical "creative brain" that can be spotted from the outside, as if using a phrenologist's chart to identify the b.u.mps of a creative person's skull. One research team, though, reported a correspondence between the brains of those who seem to be especially creative thinkers. Certain people, they found, have fewer of one kind of dopamine receptor in the thalamus of the brain. These people also performed well on tests of "divergent thinking," in which people are asked to concoct more and more elaborate uses for ordinary objects, for instance. The reduction in receptors might actually increase information flow to various parts of the brain, essentially allowing them to think up new and interesting solutions. "Thinking outside the box might be facilitated by having a somewhat less intact box," the researchers wrote.

Objects and people on our route became possibilities for interaction, rather than decoration or obstruction, as the urban pedestrian might define them. With that in mind, Kalman and I approached a streetlight. I cannot say I had ever approached a streetlight before with such antic.i.p.ation. I had walked by streetlights, run into streetlights (then cursed streetlights), watched my dog spend precious minutes smelling the urine on their bases. You have seen these lights in your city. Indeed, in New York there are two or three on each side along every city block . . . wait, have you really seen them? Yes, of course I have, you say to me impatiently. And so you have. So you know that the most common streetlight typically extends from a pole that is round or octagonal-not rectangular-or is hooked like an inverted J; that the legs of these poles are thirty feet tall, more than three times as long as the arm holding the cobra-headed lamp; that there are white and yellow sodium lightbulbs (and that we feel calmer under the yellow), which are typically one of two streetlighting wattages; that there are a variety of possible pole bases, none of which is entirely impervious to dog urine. But you are getting restless, I see, since you have seen streetlights, and you know about them already.

This streetlight pole was festooned. Someone had decorated it with a few half-hearted flyers, attached at eye height with serious packing tape. An advertis.e.m.e.nt for clarinet lessons stopped Kalman in her tracks. The bottom edge of the paper was cut into strips cut and bent hopefully for easy grabbing by clarinet-interested pa.s.sersby. Kalman grabbed one. She had begun to learn the clarinet the previous year, she revealed, as part of a project for a cla.s.s she teaches at the School of Visual Arts. For her curriculum, everyone was tasked with learning a new instrument, then taking a walk by themselves, writing down "what was going on in their minds," Kalman mused, looking at the wee bit of paper in her hand. "Then one of the students took all of the texts that they wrote and made them lyrics for a song using all the musical instruments." They were to perform the music on the street but kept being thwarted by the weather. She sighed. "So we never performed it out on the street where it was meant to be; it was meant to be walking music."

We left the flyer otherwise intact, its strips fluttering in the breeze. I did briefly consider taking up the clarinet. I could hear someone practicing piano awfully through an open first-floor window. We walked down the street to this music. The street provided the accompaniment.

1 Though she does have more ladders than one would ordinarily expect of an apartment dweller, and is drawn to rubber bands . . .

2 And so I try it! horowitzhorowitzhorowitzhorowitzhorowitzhorowitzhorowitzhorowitzhorowitzhorowitzhorowitzhorowitzhorowitzhorowitzhorowitz. . . and my last name becomes a pulsing, throbbing vowel-crushing machine.

3 It's not you, alas: any egg shape with eye shapes within it that you show to an infant will elicit coos and smiles of delight.

ANIMATE CITY:.

Everything That Won't Stand Still.

"'Tis very pregnant,

The jewel that we find, we stoop and take't Because we see it; but what we do not see We tread upon, and never think of it."

(Shakespeare).

Flipping Things Over.

"A wooly caterpillar, his head crowned with four fearsome green horns, moved lazily on the first step, heading nowhere good for caterpillars."

If you do not get excited about finding a blowfly paralyzed by a parasitic fungus on the bottom curl of a leaf tip, or upon spotting the globular, smooth-edged holes in a leaf that are the characteristic sign of a munching tortoise beetle, then perhaps a walk around your block with Charley Eiseman is not a good idea. But for anyone who as a child marveled at the metamorphosis of a homely caterpillar into an iridescent b.u.t.terfly, or who has admired the tenacity of a slug or snail a.s.siduously consuming their tomato plants, this sort of walk will open your eyes to the unnoticed population underfoot, overhead, and, alarmingly, onbody.

It is time to consider the bugs.

Even when you see no bugs before you, even when the ground looks still and the air looks clear, they are there. Millions upon millions of bugs. And there are even more signs of bugs past: on vegetation; in leaves and bark; in characteristic leavings; in egg sacs, coc.o.o.ns, spent exoskeletons, and built structures; on brick, dirt, clay, and on your own skin. Their ubiquity does not make them inherently interesting, of course. In fact, as a culture we tend to value the rare over the common, in our sensibilities and in our policies. We mourn the pa.s.senger pigeon, hunted out of existence a century ago, but vilify the pigeon on every city street; we keep bunnies and mice as pets yet kill rabbits and mice not born in pet stores. Of course, there are hundreds of rare-federally named as endangered-insects: the "superb" gra.s.shopper; eleven pomace fly species; a.s.sorted weevils, ants, beetles, and midges. But the prevalence of bugs (or, better, Arthropoda-true insects, arachnids, and otherwise) only highlights our obliviousness to them . . . most of the time: we certainly notice when a c.o.c.kroach darts across our dinner table or when a male mosquito, covering for his bloodthirsty mate, buzzes in our ear.

The insects' advocate is Charley Eiseman, a young man with a calm manner and a trim beard befitting the naturalist that he is. Though I had not met him before, he proved easy to spot: wearing a plainly genuine expression and a flannel shirt on a sixty-degree day, he stood out among city folk. Eiseman has the quiet footfalls and una.s.suming presence often found in native New Englanders. He smiled broadly in greeting, but he also looked at me a bit like he was trying to determine what kind of insect I was.

A field naturalist by training, Eiseman confessed to having an overweening sensitivity to all living things. While working out of doors teaching tracking cla.s.ses and conducting salamander surveys, he began noticing "little mystery objects"-the spoor and leavings of insects and other invertebrates. Wanting to have a field guide to these tracks, and finding none, he and his friend Noah Charney set off on a fifteen-thousand-mile, forty-day journey to doc.u.ment evidence of invertebrates-what is called sign-in all the major ecotypes in North America. The result of their travels and research was Tracks and Sign of Insects and Other Invertebrates: A Guide to North American Species. The book is a marvel: a rollicking, seemingly plumbless guide to the innumerable indicators that insects leave of their presence.

Eiseman met me on an early-September afternoon in a parking lot in Springfield, Ma.s.sachusetts, an industrial city that never had an urban reincarnation and is very unpromising for walking, as far as I was concerned. But it was near Eiseman's hometown, which is not urban at all, so this was where we converged. I asked that we meet in a parking lot on the strength of a mention in his book. In the introduction, Eiseman writes that he and Noah stopped on their invertebrate tour to visit Noah's mother in Tennessee. Five hours after they said their good-byes, Noah's mother left her house to find the fellows still in the driveway. Turning over sugar maple leaves and flipping logs, they had found enough insect sign to postpone, for the time being, their trip to the "wilderness" where real nature was to be found.

I was secretly hoping that we would not make it out of the parking lot ourselves. If a driveway holds an ecosystem, what of a parking lot? Perchance a universe. Sure enough, we were barely ten seconds into our walk before he spotted a few beautiful orb weaver webs, followed by a handful of funnel webs along a hedgerow at the lot's edge. He did not know the name of the orb weaver ("An arachnologist might be able to tell you," he said unhelpfully for those of us having no arachnologist readily available), but here, as throughout our walk, it was clear that the specific naming was not the point. Instead, the fun is the discovery of the thing at all.

The funnel webs turned out to be a repeating motif of our walk. Once we saw one, it was as though they were imprinted on us, and we were unable not to notice another. The characteristic dense white web shows up again and again-at the top of a row of hedges in front yards, along intersecting brick walls. If you look more closely, you will see the t.i.tular funnel: a smoothly rendered spout in which, if you are lucky, the spider is hiding, waiting for some walking insect to happen upon her lair and submit to her jaws.

To look at insects up close is to see the hasty cycle of birth, violent killing, and death. Few insects are humanitarians, and even herbivorous insects work great damage to the leaves, buds, gra.s.ses, and stems they eat. But Eiseman and I were looking less for insects, and more for the traces of insects past. In following their tiny footsteps, we were forensic insect hunters, looking at the evidence of their criminality they have left in their wake. Insects are messy eaters, like to storm a place and live it up, and rarely clean up after themselves (except those polite larvae that eat their own egg cases). They shed their skin, excrete w.i.l.l.y-nilly, plunder and pillage, and move on: the insect equivalent of a mad party with only hastily removed clothing, broken bottles, and other detritus left behind. Positively uncivilized.

I could have loitered over the funnel webs for a while, but Eiseman had darted off. An urban walk with Eiseman is decidedly nonlinear: one minute he is beside you, the next he has veered over to a tree pit, or to a piece of street furniture-a fireplug or lamppost-and is scrutinizing its surface for bugs. We did leave the parking lot, but over the next two and a half hours, we managed to cover but two-thirds of a mile. At that rocketing pace-about a quarter-mile in an hour-we could have been overtaken by nearly all the species we saw on our walk, including some of the larvae. This was a typical pace for Eiseman, who, as a healthy young man, takes about ten hours to complete a five-mile hike, waylaid by logs whose undersides need examining and snakes demanding pursuit. He has spent uncountable hours in a quarter-acre vacant lot in Burlington, Vermont, where he once lived: a few dozen photos for his insect guide came from that single plot.

Over those hours, on the most ordinary of city blocks, we saw nearly all the categories of insect sign mentioned in his book: egg cases (the egg sac of a common house spider along a brick wall); exuviae-a fancy word for the discarded exoskeleton of a fly (a mayfly, attracted to and molting on a streetlight); parasitism (gruesome blowflies overtaken by a paralyzing fungus); droppings (earthworm droppings, a large const.i.tuent of what we call "dirt"; jumping spider droppings, black speckles in white dots); webs ("everything has a spiderweb on it," Eiseman advised); cases (spider "retreats"-structures for temporary spider-hanging-about); leaf mines (the work of the oak-shothole leafminer, whose larvae fashion rounded holes as they eat their way into adulthood); galls (small deformities on a grape plant leaf, inside of which we found uncountable secreted orange aphidlike things); mounds (small hills with burrows in their middle erupting out little brown "sidewalk crack" ants); and even sign on vertebrate (a mosquito bite on my own calf that swelled excessively).

Though this listing belies it, our walk did not start out auspiciously. After the initial web excitement, we headed down a block that looked terrifically dull. Desultory, underwatered sycamore and London plane trees lined the edge of a tired concrete path. Nothing moved; the afternoon was hushed. We were alone on the street, with not even a bored, idle squirrel for company. But Eiseman beelined to the trees and flipped over a leaf.

"This jumped out at me," he said as I followed him, vexed. What this was was not obvious. He twisted a leaf between his fingers just overhead. I looked up at it: it looked vaguely unhealthy. Then my eyes adjusted, as if coming into a cool, dark room after a summer's afternoon outside. Suddenly I looked through the leaf-and that was when I began to see what he meant. The green tissue was peppered with black and yellow spots, "the characteristic feeding signs of the sycamore lace bugs," Eiseman explained. "They don't make holes; they just suck the green juice out and make it turn yellow." These lace bugs lived on the underside of the leaf, which, on close examination, was splattered with their excrement-those black spots. Nearly indistinguishable from the excrement was a bevy of nymphs. "They are very beautiful bugs," he said, pulling down the leaf for my examination, and in the process, raining little nymphs and young adult lace bugs all over his hair and shirt. If I squinted, and suspended disbelief, the adults were indeed almost pretty, their transparent wings crisscrossed with raised and darkened veins.

I considered these little guys while Eiseman regaled me with lace-bug trivia. The bugs are specialists, often preferring just one tree: there are sycamore lace bugs, birch tree lace bugs, and oak lace bugs. They are what is called, sweetly, true bugs: of the large order Hemiptera, which includes all sorts of bugs that do not have chewing mouthparts. Instead, the lace bugs have beaks, and invent creative ways of getting out of eggs. The oak-tree varietal grows up in tiny flip-top egg lids that pop open when they are ready to hatch.

As we moved on, I pointed out the young adult bugs now speckling him. He did a perfunctory brush at his hair and smiled: "It doesn't matter." For the rest of the walk a few lace bugs cruised happily on Eiseman's chest.

As we headed down the sidewalk, every new species of plant we came across became an opportunity: an opportunity for new evidence of an insect. In an ordinary tree pit encircling its featured tree, a few plants at its base, and tree detritus (fallen leaves, twigs, seeds or nuts or seedpod), there might be thousands of bugs and spiders and other things to munch on the bugs or spiders. Soon I was a co-partic.i.p.ant in what seemed to be the major investigative strategy of the Searcher for Invertebrate Sign: flipping things over. Flipping-Over behavior marked Eiseman's approach to most things, "if things aren't jumping out at you," he said (and hopefully they're not). Eiseman was continually turning over leaves, which were often his first approach to a tree. "If you're looking for an insect specific to a tree," he suggested, "the leaves are the place to look." Sure enough, nearly every single tree we pa.s.sed bore the sign of some bug. Holes were rife. Just as the beginning arborist begins to use a leaf to identify a tree, it is soon clear that the holes of a leaf can be used to identify the hole-maker. In the motley array of trees, tree-pit plants, and wild weeds growing roadside and between sidewalk squares on our walk, we saw a dozen different kinds of leaf holes. Apart from the tortoise beetle and shothole leafminer holes, we saw large ragged holes like those a katydid or gra.s.shopper might leave; punctuative holes that mimicked commas and semicolons; and birch leaves with neat, hole-punch circles, the sign of the aptly named leaf-cutter bee. The bee builds its nest elsewhere, but mines the leaves to make cylindrical cells for her eggs.

Other leaves were intact but unusually shiny. A resolute shiny streak indicated that a slug had been sliming along the leaf overnight. A slap-dash shining job was probably a wash of "honeydew," the clear excrement of aphids, which itself draws other bugs and birds to feed on the sticky stuff. Holes and slime are only the beginning. A single leaf, nonchalantly fanning itself in the breeze, might be the repository of one of dozens of types of sign.

"Here's something," Eiseman said-and repeated on our walk together. There was always something. In this case, it was a browned, curving scribble on a leaf. "This is a leaf mine of a fly larva," he explained, ending with a period. He must have sensed that I thought at least ellipses were due, and elaborated: "The fly inserted its egg there"-he pointed at the base of the trail-"and the larva is living between the epidermal layers, and is munching along and making a wider trail as it grows bigger."

My mind boggled a small boggle. The strip of denuded leaf we were looking at was a path cleared by a young fly who was growing up sufficiently quickly that the path he left in his wake had widened over the course of his living on that one leaf.

These leaf mines, I learned, are left mostly by moths, beetles, and flies, whose larva create a visible trail as they plow along, chomping leaf tissue. They spend their whole larval life in one leaf and then emerge as an adult. Many of the mines are very particular to the species of insect: the female always inserts her egg in a particular place, such as at the leaf's edge or base. As a result, by looking at the starting point of the mine one can (if one knows quite a bit about insects) determine the larval species that is living there. The type of trail is species-specific, too. Some leave serpentine trails that draw an inscrutable image along the canvas of the leaf. Other mines cruise along the veins of the leaf. Still others are more blotch than trail, growing pools of ungreen leaf. We saw mines that followed a serpentine course and ones that hugged the leaf 's perimeter: leaf-as-jogging-track.

It is not mines but galls that are the crowd-pleasers of the insect-track-and-sign world. "Some of the galls are what draw people in first," Eiseman said with a straight face. This was initially hard to believe. A gall is a growth, a plant tumor, caused by a critter burrowing into the tissue of the plant when it is developing. The small lump, fold, or pouch that results serves as shelter and often food for the nymphs that the midge, sawfly, moth, aphid, wasp, or mite (not technically an insect) lay in it. To my eye, many galls looked a bit cancerous, the leaf blighted or with an embarra.s.sing skin condition.

"How do the plants endure all this?" I wondered aloud. "Most of it seems so destructive."

"Being deciduous helps: they get to refresh their leaves every year. Galls are a sort of agreement that's been worked out, concentrating the damage to one spot. It gives the insect shelter and food."

"The tree doesn't get anything."

"It gets less damage."

Most galls do no serious harm to their tree hosts. Some galls are almost picturesque-and adorably named. I could imagine trying to hunt for the fuzzy red "hedgehog" gall; the flamboyant "sea urchin" gall, boldly pink and spiky; or the "wool sower gall," a soft dotted pom-pom that reaches outward like a flower.

Each of these winsome galls actually holds tiny wasp larvae that reside on oak trees. If your city has oaks, you could find galls down the street. When I returned to New York City, I was barely out of the train before I come across an oak and quickly found a gall, green and pealike, on a leaf.

I started to wonder about wasp aesthetics: their galls are architectural beauties. If not inspiration for humans, there is a theory that galls might have served as a sort of inspiration for trees. As Eiseman described it, the theory suggests that galls kick-started trees into bearing us the fleshy fruits we now cultivate greedily, such as peaches and plums. If that were the case, fruits are really just evolutionary extensions of galls, developing because of wasps laying their eggs in the plant's flowers, eventually altering the plant's genome to produce galls that become bigger and more nutritious over time.

Galls are also a very particular sign: gall insects usually choose a specific place to induce a gall, as at the midrib, edge, or underside of a leaf. Most are on leaves, but some insects choose branches, twigs, or even flowers. You can open one up to reveal the tightly packed, sleeping larval species inside-or you can just infer the species from the shape and location of the nub.

Surprisingly, those leaves that have no sign, no holes, no smattering of excrement, are themselves sign of something else. They indicate that the tree is probably not from around here. Although some bugs are generalists, knocking about in our faces or homes or wherever they can find nourishment, many are extremely plant-specific. They might be born, grow, eat, mate, and die on the same plant. One type of plant-or even one individual plant-may be their entire universe. Plants native to North America have their own community of North American bugs that have evolved to live on and with the plant. However, non-native-what are increasingly called invasive1-plants are often new enough to the area that no native bug has yet evolved to specialize in them. As a result, the invasive plants do not need to put any of their resources into defense chemicals or strategies; they can put all their energy into growing and reproducing. That is why invasive plants invade so well: they can spread quickly while native plants, struggling against the bugs, are lucky to maintain their numbers.

You can, thus, make a reasonable guess as to whether a tree is native by checking out its insect population. Walking by the lovely Norway maples, five-fingered leaves robust and hole-free, I suddenly realized that the "Norway" was not a rhetorical turn. The tree I was accustomed to seeing throughout New York City is an immigrant. Even the city Parks Department logo is a silhouette of what is probably a maple (or London plane, another non-native tree) leaf. The trees we pa.s.sed looked gorgeous, each leaf custom-printed, dry-cleaned, and pressed. And largely sign-free.

Though Eiseman had not given any urban insect-sign tours, I was starting to think there may be a call for them. One might imagine that a typical city does not host too many bugs (outside of c.o.c.kroaches and bedbugs); this walk was convincing me otherwise. Eiseman flipped over a stone and rocked a log with the toe of his shoe, causing shiny dark bugs to move quickly under the nearest leaf litter. In some ways, he suggested, cities are not unnatural so much as they are concentrated nature. On his cross-country tour, highway rest areas turned out to be gold mines for bug-tracking. "It almost seems like in someplace like that, where there is just a little sc.r.a.p of nature, life is more condensed." Upon entering Texas, they discovered the Texas leaf-cutter ant at the parking lot where they had pulled over for a pit stop. Then, on going into national parkland, "we barely saw anything," he said. The density of insect life was not the same, or maybe the method of exploring-wandering along waiting for something to pop up, rather than poking into every crevice at the rest area-is not conducive to finding sign.

Certainly if a rest area provides opportunity to find sign of insect life, a city must. Eiseman cataloged some urban elements that lead to good insect-sign hunting-beginning with the city's tendency to never shut down. When Wabash, Indiana, was the first town to light itself up at night with electric light, onlookers were flabbergasted: when the lights went on, "people stood overwhelmed with awe," the local paper reported. "Men fell on their knees, groans were uttered at the sight, and many were dumb with amazement." We have grown accustomed to the ordinariness of nighttime lighting, but many insects are still in its thrall. Lit all the time, cities attract insects whose compound eyes are specially tuned to the short wavelengths of UV light, found in incandescent lamps and many fluorescent lamps. City streetlights are now usually a more energy-efficient sort, such as high-pressure sodium vapor lamps, which emit less UV light but are still a siren call for various fliers. Insects use these light waves to find and choose mates, navigate, hunt, even migrate. So they must get very excited to find UV radiating toward them at every address and along every street. The UV-seekers include moths, of course, but also beetles, lacewings, things lacewings eat (aphids), various flies (caddis-, crane-, hover-, true-, scorpion-, damsel-, dragon-, even b.u.t.ter-), and wasps. About a third of them will perish in their excitement to touch the light. They hit the hot light, circle around it until exhausted, or make enough of a ruckus that a predator (bird or bat or other insect) gobbles them up.

Other urban elements are conducive to the insect hunt. If there is a waterway near a city, you can expect that there are all kinds of mayflies and stoneflies nearby, who lay their eggs on the lampposts, and, as we saw on our walk, often molt their white filamentous skin and leave it there, quivering in the wind like the clarinet lessons Maira Kalman plucked from their flyer. Walls, especially brick walls, provide nooks that house coc.o.o.ns or nests. On the first brick wall we approached, we saw jumping spiders-and jumping spider "retreats," which sound like summer homes for spiders but are just the places where they hide but do not lay eggs. We found an egg sac of a common house spider. We found bee and wasp nests punched into tiny holes in a wall. If you are lucky, you might see a leafcutter bee nest, which features the packets of leaf bits that they have collected, each with a ball of pollen, nectar, and an egg inside. If you are less lucky, you might find a paralyzed cricket stashed by a wasp in a hole stoppered with gra.s.s or mud.

Abandoned places, something cities provide in abundance, are "promising" in Eiseman's eyes. A dusty, unpeopled overpa.s.s is a great substrate for insect tracks. Old Dumpsters attract coc.o.o.ns and spiderwebs. "I did see a gra.s.shopper munching on the paint on the corner of my house one time," he added. We were poking around a Dumpster together. Eiseman naturally got much closer than I would. It was only when perched on its wall that he spied a downy woodp.e.c.k.e.r on a nearby tree making a rhythmic racket.