Mr. Bulger is making initial appearances in two separate cases from 1995 and 1999, according to the United States Attorney’s office. He faces federal racketeering charges in connection with murder, extortion, money laundering and other crimes.

Ms. Greig, who faces the lesser charge of harboring a fugitive, will appear afterward in a separate courtroom.

They seemed to be just another fading, elderly couple -- Charlie and Carol Gasko -- enjoying retirement in a modest apartment building a few blocks from the Pacific in Santa Monica. He told a neighbor he had emphysema and spent his days lying on the couch watching television. Carol would venture out for strolls on the nearby Third Street Promenade, stopping by the Saturday Farmers’ Market or feeding a neighborhood stray cat. Often, he tagged along.

But they were reclusive and a little odd, neighbors said. Charlie would often wear a baseball cap or fedora that shadowed his face. He would bark at neighbors when Carol lingered too long to speak to them, said one neighbor, who described him as “a rageaholic”; Carol explained that he was suffering from dementia. In recent months, another neighbor said, a note was taped to their door reading, “Please do not Knock at Any Time.”

But the couple who led this quiet life for more than a decade were not who they said they were.

Charlie Gasko was a notorious gangster — Mr. Bulger, once Boston’s most fearsome crime boss, a fixture on the Federal Bureau of Investigation’s 10 Most Wanted list — and she was his girlfriend, Ms. Greig, 60. They fled more than 16 years ago after Mr. Bulger, a sometime bureau informer, learned from a retired F.B.I. agent that he was about to be arrested.

The long manhunt — which had produced Elvis-like Bulger sightings around the world, rumors of his death and considerable embarrassment for the F.B.I. — ended shortly after 5 p.m. Wednesday when agents lured them out of their apartment and put them under arrest. Mr. Bulger, 81, offered no resistance as his long run as a fugitive ended and he came face to face with accusations of killing 19 people and other crimes, the authorities said.

Appearing in Federal District Court in Los Angeles on Thursday, Mr. Bulger and Ms. Greig waived their right to fight their return to Boston and agreed to go back. Mr. Bulger — wearing a white shirt and blue jeans, and sporting a thick white beard — sat at the front, looking straight over the courtroom, grinning as he surveyed the scene. Ms. Grieg appeared spectral, with short white hair and sunken cheeks.

When Magistrate John McDermott asked Mr. Bulger if he had read the indictment, he responded in a thick Boston accent. “I got them all here,” Mr. Bulger said. “It will take me quite a while to finish these. But I know them all pretty much.”

The end came just days after the F.B.I., increasingly frustrated at the continued elusiveness of Mr. Bulger — who had a $2 million bounty on his head — decided the best way to find the mobster was through his girlfriend. There had been no sightings of Ms. Greig, a former dental hygienist, since her disappearance, leading F.B.I. officials to assume she was at his side. And she was a person with the kind of idiosyncrasies — a devotion to animals, the beauty parlor and monthly teeth cleanings — that might make her easier to find, they figured, especially given the assumption that the couple had altered their physical appearance with plastic surgery.

The F.B.I. doubled the reward for her capture — to $100,000 — and began broadcasting public service advertisements this week in 14 cities, during daytime television shows favored by older women.

The improbable end to a hunt that many people had long assumed had turned cold riveted his neighbors in Santa Monica, but even more so the people back in his old haunts in South Boston, where Whitey had been a legendary mobster — a hero to some, but loathed by many — who had helped define a Boston of old. The news that he had been caught, that he was still alive, was, for Boston, a hometown version of the killing of Osama bin Laden, who until last month shared with Mr. Bulger a listing on the F.B.I. fugitive list.

“I was shocked,” said Mary Child, 75, who grew up around the corner from Mr. Bulger in the Old Harbor Housing Project in South Boston. “It’s the end of an era.”

Paul McGrath, 47, a union stagehand and Teamsters member, said he hoped Mr. Bulger’s capture would remove what he believes to be a stain on the neighborhood where he was raised.

“A lot of honest blue-collar people built South Boston,” Mr. McGrath said. “Not everyone here is a gangster. As soon as you say you’re from South Boston, the conversation stops because everyone, including the F.B.I., thinks you have the back of Whitey Bulger. It’s unfair.”

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This photo from WCVB-TV in Boston shows James Bulger and Catherine Greig after their arrest.

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Federal agents seized evidence from the apartment of James (Whitey) Bulger and his companion, Catherine Greig.

Renown in South Boston

It is difficult to overstate the role of Mr. Bulger and his vanishing act in Boston culture and lore. People in Boston learn his name and story in childhood; many can point out the landmarks associated with his criminal reign, like the liquor store on Old Colony Avenue in South Boston that served as his longtime headquarters.

He was an inspiration for Jack Nicholson’s Irish mob boss in the movie “The Departed,” set in Boston. And books on Mr. Bulger continue to be published, including a new one by Kevin Weeks, one of his former associates, called “Where’s Whitey?”

Southie, as the neighborhood is known, was Mr. Bulger’s home since childhood, when his shock of white-blond hair earned him the nickname that would stick — to his annoyance, it was said — for life. Many there were terrified of Mr. Bulger, known for his violent temper; others considered him a Robin Hood figure who looked out for his neighbors.

A troublemaker from an early age, Mr. Bulger joined the Air Force in 1949, when he was 20, but was discharged three years later after going absent without leave. He returned to Boston and began a life of crime; by 1956, he had been sentenced to prison for his involvement in a string of bank robberies. He spent part of his sentence on Alcatraz Island.

Back in Boston, he joined the infamous Winter Hill Gang, which came to dominate organized crime in Southie and the city’s other Irish neighborhoods. He ultimately became a leader of the gang along with Stephen (the Rifleman) Flemmi.

Prosecutors would later describe the pair as the kind of territorial bosses who would demand protection money from bookmakers, loan sharks and other petty criminals, and who were also involved in illegal gambling enterprises and loan sharking themselves. Mr. Bulger was known for his almost maniacal cruelty, like strangling the girlfriends of two of his lieutenants.

“The saying in Southie used to be that when Whitey walked down the street, the sidewalk shook,” said Robert Stutman, who headed the Boston office of the Drug Enforcement Agency in the 1980s. “In my opinion, Whitey was more feared in Boston than John Gotti was in New York.”

Mr. Bulger’s already outsize life took on another surreal dimension in the mid-1970s, when the F.B.I. recruited him as an informer in its mission to close down a rival criminal organization: the New England branch of the Mafia. Agents who worked with Mr. Bulger allowed him to continue his criminal activities, ostensibly as long as no violence was committed.

But evidence later emerged that Mr. Bulger and Mr. Flemmi were involved in gruesome murders while serving as informers. Other law enforcement agencies, including the D.E.A. and the Massachusetts State Police, opened investigations into Mr. Bulger’s criminal activities while he was an F.B.I. informer, but it was later revealed that he had been tipped off or protected by his F.B.I. allies.

Such actions, revealed in a racketeering case against Mr. Bulger in the late ’90s, became a huge embarrassment for the F.B.I. In 2003, a report by a Congressional committee called it “one of the greatest failures in the history of federal law enforcement.”

The F.B.I. agent whom Mr. Bulger had worked with most closely, John Connolly Jr., tipped him off about his imminent arrest in December 1994, according to court testimony. Mr. Bulger fled to New York that night.

When revelations of his arrangement with Mr. Connolly emerged, the F.B.I.’s role in Mr. Bulger’s disappearance became almost legend in Boston. Many residents believed the F.B.I. had intentionally chosen not to catch Mr. Bulger out of fear that he would reveal more embarrassing secrets about its dealings with him.

But most of the agents from Mr. Bulger’s days in Boston are retired or dead now. Dick Lehr, a former Boston Globe reporter who was an author of a book about Mr. Bulger, “Black Mass: The True Story of an Unholy Alliance Between the F.B.I. and the Irish Mob,” said the newer generation of F.B.I. agents had been determined to catch him.

“In recent times, they really wanted him,” Mr. Lehr said. “There’s been this cloud over the Boston office.”

Federal officials appeared eager to remove that cloud on Thursday. “Although there are those that have doubted our resolve at times over the years,” said Richard DesLauriers, the special agent in charge of the F.B.I.’s Boston office, “we have never wavered.”

FBI, via Associated Press

Photos of James (Whitey) Bulger in 1984 from the F.B.I.

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James “Whitey” Bulger

Tracing the path of a fugitive.

Related

• Times Topic: James (Whitey) Bulger

• In South Boston, Mixed Memories of Whitey Bulger (June 24, 2011)

• And Then There Were Eight (on the F.B.I.’s List of the Most Wanted Fugitives) (June 24, 2011)

• Wanted: Hygienist (and Her Gangster Pal) (June 21, 2011)

  F.B.I. Video via YouTube: Have You Seen This Woman?

Michael Dwyer/Associated Press

The couple's capture came only days after the F.B.I. began a new advertising campaign asking the public for any information about their whereabouts.

Monica Almeida/The New York Times

Neighbors in Santa Monica knew them as Charlie and Carol Gasko.

A Sunny Hideout

Santa Monica was a place where the couple could disappear into a backdrop of palm trees, skaters and endless beach, a diverse community that includes many transplanted people from the East Coast. Their building was just off the corner of Third Street and Washington Avenue, an easy walk to the park overlooking the ocean, Santa Monica Beach and the Farmers’ Market.

Their apartment — an 1,000-square-foot two bedroom on the third floor — was rent-controlled and cost them $1,145 a month, which they always paid in cash. Joshua Bond, the building manager, said they had lived in the building since at least 1996 and had given him a cowboy hat.

By many accounts, they did not resemble the photos on the F.B.I. posters. “They look like they had a lot of work done,” said Julie Craig, 55, who lives on the same floor of the building.

Barbara Gluck, a neighbor, described Ms. Greig as a “lovely person,” but added: “He, on the other hand, when we talked too long, would shout, ‘Stop talking, let’s go.’ ” Janus Goodwin, 61, said she visited them in the apartment. “When I would be invited in, he would always be lying on the sofa, watching TV,” she said. “He was very proud of his little art pieces, which were cheap knockoffs of Monet and Van Gogh.”

Ms. Goodwin said Ms. Grieg had blond hair and was always nicely dressed; Mr. Bulger would appear in dress shirts and dark pants, and had dark hair, which she assumed was dyed.

“I’m kind of shocked, really,” she said. “I’m not quite processing it all quite yet. I’ve been crying a lot.”

An Ad Campaign Pays Off

Mr. DesLauriers, the special agent, said that the tip that led to the arrest came into the F.B.I. just after 11 p.m. Tuesday, and that it was a “direct result” of the campaign that began Monday aimed at drawing attention to Ms. Greig.

“We quickly recognized that the information appeared to be credible and promising,” he said.

On Wednesday morning, he said, agents from the F.B.I.’s fugitive task force in Los Angeles opened a surveillance operation at the apartment on Third Street. By 4 p.m., the F.B.I. concluded the tip was correct, after agents observed a man and a woman who resembled Mr. Bulger and Ms. Greig leaving the building. Agents lured Mr. Bulger out of the apartment using a ruse about 5:45 p.m., Mr. DesLauriers said. Inside the apartment, they found more than $800,000 and more than 20 firearms, including handguns and several longer guns. They also found knives and false IDs, according to the F.B.I.

Carmen Ortiz, the United States attorney in Boston, said that Mr. Bulger could get life in prison in the federal case here but that he could face the death penalty in two separate pending cases in Oklahoma and Florida. Within hours of his capture, Katherine Fernandez Rundle, the Miami-Dade state attorney, said she was eager to try him on charges of orchestrating a 1982 murder of a gambling executive at Miami International Airport. If convicted, Mr. Bulger could face the death penalty.

Back in Boston, family members of others believed to be Mr. Bulger’s victims were still absorbing the events taking place 3,000 miles away. “I never thought I’d see this day,” said Patricia Donahue, whose husband, Michael, was a bystander in a killing Mr. Bulger is accused of committing in 1982. “I have satisfaction and despair, because it brings back so many old memories. But satisfaction that they have him.”

Adam Nagourney reported from Los Angeles, and Abby Goodnough from Boston. Reporting was contributed by Jennifer Medina from Santa Monica, Calif., Ian Lovett from Los Angeles, Charlie Savage from Washington, Katie Zezima from Boston, and Michael Cooper and William K. Rashbaum from New York.

This article has been revised to reflect the following correction:

Correction: June 23, 2011

A previous version of this story contained an incorrect first name for Richard DesLauriers. An earlier version also misstated the location in Santa Monica of the apartment building where Mr. Bulger and Ms. Greig lived and were arrested. It is just off the corner of Third Street and Washington Avenue, not on the corner of Third Street and California Avenue, which is a block south.

• © 2011 The New York Times Company. Reprinted from The New York Times, National, of Thursday, June 23, 2011.