The sign in Antoine Philippe Dorcelus's yellow cab clearly stated that the maximum number of passengers was four. But Mr. Dorcelus didn't bat an eye when 13,000 bees buzzed into the taxi's front seat the other day in the company of a man named David Graves.

Mr. Graves is a beekeeper from Becket, Mass., and his traveling companions, clustered in a footlong box with wire-mesh sides, were Italian honeybees, which he intended to install in an empty hive on the roof of an East Village hotel. Mr. Graves, a serene 55-year-old with a helmet of gray hair, keeps 14 active beehives on rooftops scattered around New York City.

Although finding a cabdriver willing to tolerate thousands of live bees as passengers might seem challenging, almost nothing could give more pleasure to Mr. Dorcelus, who in the past two years has evolved into both a good friend and an unlikely beekeeper's apprentice to Mr. Graves.

Indeed, it was Mr. Dorcelus, a 52-year-old Haitian immigrant with a bushy, white-tipped black beard, who first approached Mr. Graves in spring 2004 at the Union Square Greenmarket to pepper him with questions about beekeeping. Mr. Graves is a fixture at the market, where he sells the high-rise honey he harvests from his rooftop hives, whose locations include a soul-food restaurant in Harlem to an Episcopalian church in Midtown.

"He's getting so well versed," Mr. Graves said of Mr. Dorcelus, "that I'm learning from him, too."

Before immigrating to New York from Haiti in 1983, Mr. Dorcelus bought a small plot of land in his hometown, St. Michel, which he dreams of one day turning into a farm. He hopes to plant fruit trees, and during his research he discovered that honeybees are a terrific way to pollinate the trees' flowers and ensure a good harvest.

Ever since, Mr. Dorcelus has devoted himself with tireless passion to learning everything he can about farming. At home in Canarsie, Brooklyn, where he lives with his wife and two children, he watches how-to videos about artificially inseminating turkeys. While waiting for fares at La Guardia Airport, he pores over The American Bee Journal.

But there is only so much a man can learn about beekeeping while sitting behind the wheel of a cab or in front of his VCR. "I'd already looked at four videos and read at least 20 books on bees," Mr. Dorcelus said, "but I had never touched bees."

It was to gain hands-on experience that Mr. Dorcelus marched up to Mr. Graves's farm stand two years ago and announced that he would like Mr. Graves to help him master the beekeeper's craft. "At first I was a little apprehensive," Mr. Graves recalled. "This was a complete stranger coming up to me. And a cabdriver, no less."

But Mr. Dorcelus was persistent, so after Mr. Graves got a character reference from a chicken farmer who was a mutual friend, he decided to give Mr. Dorcelus a chance.

In this way, Mr. Graves became perhaps the only man in New York who never has trouble finding a taxi. Any time he needs to visit one of his hives, he simply calls Mr. Dorcelus, who promptly illuminates his yellow cab's "off duty" sign and hurries to the Union Square Greenmarket.

This particular day, as Mr. Dorcelus pointed his cab down Union Square West, leaving the greenmarket behind, Mr. Graves, who was sitting in the front seat, held up the box of bees next to the meter.

"This company is good," Mr. Graves said, referring to a Georgia farm that had filled the box with three pounds of honeybees so hardy that they had traveled through the mail in good health.

After weaving the cab among bike messengers and shrieking ambulances, Mr. Dorcelus parked near the East Village hotel, and the two men walked across its lobby with their bees and rode the elevator to the top floor, the 12th.

On the tar roof, Mr. Graves took out a spray bottle full of sugar water and sprayed it through the mesh sides of their box so as to coat the bees with its contents. The two men watched as thousands of tiny brown tongues flicked through the mesh to consume the sweet-smelling liquid. "I want them to load up on it so they don't fly in my face when I stick them in the hive," Mr. Graves explained.

Next, the two men ascended to a second, smaller roof, by engaging in a feat of high-altitude beekeeping unlikely to have been covered in any of Mr. Dorcelus's instructional videos.

After climbing a weather-beaten ladder attached to the elevator motor room, Mr. Graves grabbed the metal loop of a window sash and shuffled gingerly across a rusty metal pole he had placed horizontally as a precarious six-foot bridge between the ladder and the tiny roof. He then talked Mr. Dorcelus through the same maneuver.

In the shadow of a water tower, just a few feet from the roof's edge and a 120-foot drop to the ground, stood the hive: a wooden box the size of a small file cabinet. Mr. Graves removed the top to reveal several rectangular wooden frames, each enclosing a honeycomb and resting vertically inside the box like a file.

Mr. Dorcelus handed Mr. Graves a honey-glazed frame taken from an uptown hive. Mr. Graves slipped the frame into the empty hive as a welcoming meal for the new out-of-town bees. Then Mr. Graves pried open the lid of the bee package with a screwdriver and carefully spilled some of the drowsy, sugar-coated bees into the hive. He then placed the open box inside the hive so the rest of the bees could exit at their leisure.

A few minutes later, Mr. Dorcelus leaned over the edge of the roof and scanned the city below for likely pollen sources.

"They got the locust tree right there," he said, pointing toward a flowering tree 12 floors below. "And the crabapple's got flowers."

Mr. Graves nodded. Two years into their friendship, the Massachusetts farmer and the Haitian cabbie have developed such a close working relationship that Mr. Graves is grateful he has never two-timed Mr. Dorcelus with another cabdriver, as almost happened last year.

In winter 2005, an Indian cabbie named Abdul presented himself at Mr. Graves's Union Square farm stand and began hounding him with requests to visit hives, just as Mr. Dorcelus first had the year before. To test the man's reliability, Mr. Graves gave him some wood and asked him to take it home and make some honeycomb frames. But the man never returned.

"I didn't really want Antoine to find out, because I thought he'd get upset," Mr. Graves said. "So it's kind of a godsend that the guy never came back."

After all, Mr. Graves added, "I had a good thing going with Antoine."