Government is said to work at a snail's pace. And so it has been with the Virginia Department of Transportation and its hand-wringing over whether to reduce from three to two the number of occupants needed for a vehicle to use the HOV lanes on Interstate 95. The debate involves studies of traffic patterns, peak-hour utilization statistics, the changing eco-demographics of suburbia, per capita gasoline expenditures, and so on.

But as usual, government is missing the main point, which is ecology, not economy. The environmental impact must be weighed. An innocent, indigenous species is threatened with extinction.

Before it is too late, here is a plea for the common slug.

Finding out where and when slugs come out is easy: Ask any suburbanite working in a government building downtown and if he can't tell you, he knows someone who can. Spotting slugs, however, is another matter. It can be a slippery business.

I arrive at D and 7th streets SW, one of two popular pickup points downtown. (The other is at 14th and Constitution.) It is 3:30 on a weekday, and I am assured the slugs will be here.

But where? What does a slug look like? How does he behave? What distinguishes him from the more conventional commuter? At the corner, a lone man in a gray suit waits at a bus stop. Behind him, a handful of pedestrians scurry by, heads tucked down, briefcases clamped to their sides. Otherwise the pavement is empty.

Suddenly, three men and one woman line up alongside a low wall, their eyes riveted on the street, alert, aquiline, predatory. A fifth, then a sixth commuter joins them. It is as though they are obeying some timeless imperative, a signal only they can hear. Pretty soon a queue of people in business suits extends to the corner. A car draws up to the curb and idles. The passenger window slithers down and a voice calls out, "Bob's." Without a word and only a quick glance left and right, three bodies peel away from the queue, sidle into the car and disappear down the street. The next car pulls up, and the ritual repeats itself, with only one variation. This time, instead of "Bob's" the voice says, "Rolling Valley."

I have found them. Our indigenous slugs, working men and women who have evolved a method of commuting that is more flexible than carpooling, more comfortable than buses, and free. It is based on a simple trade of goods: Slugs lend their bodies to drivers who want to use the HOV-3 lanes; in return, drivers supply rides between predetermined pickup points. Slugs are living, breathing proof that life spontaneously organizes itself into complex adaptive systems.

Theirs is a complicated anthropology. They have a finely tuned code of behavior, a remarkable resilience and even their own language. In slug-lingo, "Bob's" means "across the street from Shoney's on Old Keene Mill Road." The verb "to slug" embodies the paradoxical concept of inactive action. They get around. They just don't have to work very hard at it.

D.C.'s slugs have been with us for more than 20 years, undeterred by the expansion of mass transit, by suburban sprawl. New Metro stations? They couldn't care less.

Ah, but when you broach the news that HOV-3 lanes might change to HOV-2, they react as though you've sprinkled them with salt. Up and down the line, slugs writhe, cringe, groan.

When the HOV-4 turned into HOV-3 in January 1989, the effect on slugs was undetectable. But another reduction would put them on the endangered list by making carpooling almost as flexible as slugging. Anybody can scrape up a spouse or a neighbor who needs a lift. "We'd lose a lot of people," says Kenny McClevey, who slugs from Springfield to the Department of Energy. "It would congest the HOV lane," he says, making the whole enterprise less desirable, seriously undercutting the market value of the slug. In a Constitutional sense, it would be depriving persons of property without due compensation.

Reduce the HOV requirement? Slugs would feel slimed. Slug Lore

As with the Mayans and the Etruscans before them, the origin of slugs is largely a matter of myth and informed conjecture. The consensus is that their evolution began some 20 years ago, that it was sparked by the HOV lanes that opened in December 1973 on I-395 and I-95, and that -- as with so many mysteries in life -- it originated with the Pentagon.

"It is my understanding," says Phil Hoffman, a Foreign Service officer with a fascination for slugs, "that it began with people waiting at bus stops on their way to the Pentagon." Car poolers who found themselves a person short would pull up and offer the commuter a ride. Given the choice of waiting up to 20 minutes for a bus on which he might have to stand, or easing into the backseat of a sedan, the commuter usually opted for temperature control and upholstery. And, thus cocooned, this life form began to metamorphose.

Pretty soon, drivers who wanted to shave time off their commute to and from the Pentagon began to cruise the bus stops, while commuters who liked the idea of saving money and time queued up for rides. This happened at a place still referred to as Bob's, at the intersection of Bland Street and Old Keene Mill Road in Springfield.

"Bob's was a Big Boy's which Shoney's later bought," explains Rich Rineer of Burke, who became a slug 13 years ago when working at the White House. "But," he adds, "the Long John Silver's across the street is actually the pickup point." Slugs respect history, and so the spot is still called "Bob's."

"In the early days," Rineer recalls, "there was a theater near Bob's, and you could buy parking spaces. It was a dollar a day and for every dollar you spent the theater owner gave you a dollar discount on a ticket." The perfect slug deal: cheap parking that translated into free movies. But then Circuit City bought the lot and disallowed parking. Slugs sloughed off their cars across the street, but the businesses soon vetoed that. At once slugs began slinking off into neighborhood streets, discarding their vehicles in residential areas. But the police ticketed them mercilessly.

So, once again, the slugs adapted. They still pick up rides at Bob's, and get dropped off in the evening at the Shoney's across the street. And they still, sniffs Shoney's manager Stephanie Levay, "don't buy a darn thing."

The difference is that now they get family members to drop them off or they walk to the pickup point. A few lucky early birds park in the small lot behind Chi-Chi's in Springfield.

And others, like Rineer, migrated to Rolling Valley Mall.

It is there, at 7:30 on a sunny morning, that, in the manner of Margaret Mead and Jane Goodall, I myself will become one with the slugs. Slug Safari

As I drive down Old Keene Mill Road, west of Springfield Plaza, beyond the Golf Club, farther out into the suburbs than I have ever been, I finally spot Rolling Valley Mall on the right. I see a stream of cars exiting the mall's parking area, always three passengers to a car. Slugs.

Inside the parking lot, I spot people queuing up alongside the bus stop. Slug line.

I park in the adjoining commuter area and take my place behind a young man in shirt sleeves.

Within seconds, the line extends behind me.

The ritual that unfolds is ingeniously simple. Cars drive in from the opposite end, passenger window rolled down. As they come to a stop, the slug at the head of the queue walks the length of the line shouting the drivers' destinations back to the waiting slugs.

"K and 18th!" "Crystal City!" "L'Enfant Plaza!" "State Department!" Even an occasional "Capitol Hill!"

With each call, two slugs leave the line, but not before they've made sure nobody ahead of them wants the ride. Slug etiquette.

When the lead slug hops in a car, the next one moves up to take over as the caller. Occasionally, a driver will be looking for a special slug, and selects him or her from deep in the line. This is known as a "will call," one of the men explains to me. "It is perfectly acceptable," he mutters. In the world of slugs, drivers call the shots; you have to respect it, but you don't have to like it.

All slugs, however, are created equal. When an elderly woman misunderstands the cues and jumps ahead of the line, everybody squirms. Sensing her mistake, she stops, looks around in confusion. Head bobbing apologetically, she resumes her place.

"Jumping the line is a real no-no," murmurs a man, who does not have time to divulge his name. A voice has called "Pentagon!" and he's off.

I am now one slug away from taking the lead. When I hear the call "Smithsonian!" I dash forward, even though I am really headed for Capitol Hill. I just can't hack the responsibility of being Head Slug. Not on my first day.

As I reach the Toyota Camry, I see that the driver is a man, and there is a female slug already in the back seat. I wonder at the woman's presumption: Does one treat one's driver as though he were a cabbie, or as though he were a friend? Is it wrong to seem too familiar? I have a choice to make, and I make it. I get in front. The driver doesn't seem to mind. I settle in, briefcase at my feet, handbag in my lap.

I'm comfortable, no doubt about it. Far more comfortable than on any bus or Metro, but the slug skin still feels alien. In the backseat, the other slug works a rosary, lips moving silently, beads slipping steadily through her fingers. I find this unsettling.

Not a word has been spoken. There is a palpable atmosphere of commerce and entitlement. I steal a glance at the driver. He is an Indian man in his late forties or early fifties. He looks pleasant and sober. Quiet. Yet not too quiet. Not the loner type whom everyone later remembers as sticking to himself and causing no trouble. Later, I would ask his name. Rajeev Railan works at the Department of Energy. He doesn't speed, doesn't weave.

Then the Toyota noses onto the I-395 ramp, and my disquiet melts. My fingers relax. I savor the smell of the leather upholstery, the gentle breeze that pours in from the vent, the happy tune on the oldies station. To my right, an unending convoy of cars blurs into a variegated unmoving mass as the Toyota speeds up the HOV ramp and zooms down the highway.

(At latest count, some 5,500 cars drive under the aegis of the HOV diamond every rush hour. Nothing compared with the more than 96,000 that choke the general lanes, angry brake lights flaring.)

In town, Railan drops the backseat slug off at the entrance to her workplace. Even with this two-block detour -- a standard service drivers provide -- the trip from Rolling Valley Mall to the Smithsonian has lasted a mere 25 minutes.

"Today," Railan says proudly, "I probably saved 40 minutes. Maybe more." Railan, it turns out, has never slugged, just as most slugs have never driven.

Slugs only rarely mutate into drivers, and vice versa. Slug Redux

It is afternoon. I am loping toward the Washington Monument, steering for the slug line that stretches along 14th Street. I join it.

When it is time, I unhesitatingly take the lead, walking up the parade of cars, pausing at each to relay its destination to my fellow slugs who wait patiently, in a single file. Most of the cars are headed for Bob's, but in six minutes I am comfortably settled in a van speeding to a rendezvous with my car at Rolling Valley.

Some slugs, like me, are made. Some are to slugdom born.

William Faith of Springfield tells of dropping his father off at the line on his way to school in the morning; today, he has been slugging for eight years. Others are introduced to the slug line by colleagues or neighbors and yet others begin as car poolers.

Laura Vasquez, who slugs from 7th and D, defected from her car pool in February. "Now I don't need to rush to meet the car pool," she says. "If I work late or need to leave early it isn't a problem."

And then there are those who inadvertently stumble into this new incarnation.

"Just the other day," Rineer recounts, "there was a young woman sitting at the bus stop. I told her she could wait another 20 minutes or get a ride immediately. She took the ride." He adds gleefully: "My bet is she's a convert."

If so, it probably will not take her long to learn the other mores in effect in slug land.

"Body snatching" is considered gauche. This is the practice of drivers who cruise the neighborhood to snatch approaching slugs before they reach the line. Uh-uh. If you want a slug, you must line up for one.

Slugs have rights, too. They have the right of refusal -- there are anecdotes of slugs shaking their heads at an old Honda, opting instead for the new Volvo that just pulled up. Slugs will move on if they spot trash on the floor. They are not animals.

"Sometimes I haven't gotten in if the people give me the creeps," says a slug named Teresa. But this is rare. Teresa loves slugging, so much so that she travels by Metro from Dupont Circle to 7th and D, and then slugs home.

There are other rules, too. There is no smoking, no money changes hands, and slugs wait for the driver to initiate conversation. Conversation has its own rules.

"No sex, no religion, no politics," says Paul DesJardin, who slugs from Lake Ridge in Prince William County to the Pentagon. "Although," he adds, "all three creep in."

Drivers who aren't in a talkative mood usually play the radio or a tape softly, but occasionally one will turn the volume up high. At the mere recounting of such an incident, the line quivers with disgust.

"All the driver has to do is ask us not to talk," one irate slug grumbles. "No need to drown us out." Up and down the line, slug heads nod.

As for getting into a car with strangers, this isn't a problem. "They're government workers," Vasquez reasons. "They're harmless."

Even cautious, conservative Railan says he would not hesitate to let his 19-year-old daughter slug into town, and in his 13 slug years Rineer has heard of only two criminal incidents: Both muggings, and both crimes of opportunity on dark winter mornings when the line happened to be relatively slugless. Which brings up another rule, Railan says: "In winter, when it's dark, the line will not leave a woman alone standing on the street." If she's going to Bob's and the only other slug is going to Rolling Valley, he adds, the second slug will wait with her until a car headed for Bob's comes along.

Shirley, a mom who pulls up to the D Street pickup point at 5 p.m., says she's willing to hover here till 6 looking for a rider. "If that's what it takes," she says, scanning the empty sidewalk. Beside her, in the passenger seat, her son munches a burrito. "It's worth it," she says. "One rider saves me an hour in commuting time."

Besides, she brags, she never has had to wait long. Sure enough, within minutes a slug lumbers up to her station wagon. "Rolling Valley?" he asks. She nods, the slug gets in and off they zoom.

There is a palpable camaraderie on the slug line and -- driver willing -- in the car. At the slug line on D Street, a tall man with reddish-brown hair asks a blond woman how her interview went this morning. In great detail she tells him. Neither, it turns out, knows each other's name.

"If we run into each other outside," Rineer says, referring to the vast non-slug world he inhabits outside of rush hour, "my wife wants me to introduce them. I can't." Yet he has over the years made friends with fellow slugs and, in time, exchanged such worldly information as first and last names and telephone numbers. He has helped a slug-turned-friend build a deck and has even used the ride to and from the city for networking. According to Rineer, who now works at the Education Department, "a lot of government business is done in the HOV lane."

During rush hour, that is. After rush hour, when HOV requirements disappear, slugs tend to metamorphose into regular folks who have to shell out for a Metro ticket. But drivers leaving after rush hour have been known to swing past a pickup point just to make sure there are no stragglers.

It is this extraordinary level of civility and courtesy, the glue of a slug civilization, that is threatened now with extinction.

The Virginia Department of Transportation says slugs have not been silent.

"We've gotten letters," says transportation engineer Marsha Fiol, dryly. It is likely, she predicts, that the views of slugs will be factored in to the final decision.

Factored in? Weighed against a thousand soulless other concerns? Does the government really understand the loss to our eco-system if this life form is to disappear?

I contemplate this as the van in which I am slugging home pulls into Rolling Valley Mall. Each slug thanks the driver -- the only communication during this ride -- and the van pulls away. It is warm but still I feel a chill in the air as we slugs make our way toward the row of parked cars.

It is late afternoon, and our shadows stretch large and forbidding, toward an uncertain horizon.