While crime in the city has decreased at a rapid clip in virtually all categories, the number of arrests of female juveniles has risen in the past few years, statistics from the New York Police Department show.

Arrests of male juveniles, too, have been climbing since 2002, as the percentage of females among youths between ages 7 and 15 arrested for felonies, misdemeanors, and violations has been inching up, according to the police data.

On Wednesday, inside the Acorn High School for Social Justice in Brooklyn, a 15-year-old allegedly stabbed an 18-year-old in the head, neck, and arms with a knife. The 15-year-old was arrested and charged with first-degree assault and criminal possession of a weapon. The motive for the attack, police said, was to settle unfinished business from a previous fight between the teenagers.

Crimes like that one, social-service workers said, have become all too familiar.

In one assault report, two sisters, 13 and 14, followed another girl home from a charter school in Manhattan, punched her in the face, clawed at her hair, smashed her head into a deli window, and kicked her again and again as she lay on the sidewalk. The allegation was that someone had called someone else a lesbian. All involved were honor roll students.

In yet another report, a group of female teenagers pounced on an elderly woman carrying groceries, wrestled her to the ground, punched her in the face, and stole her pocketbook and jewelry.

One 17-year-old, Heaven Grace, told The New York Sun that she has been in so many fights in recent years that she stopped counting them.

“Women have no tolerance,” she said. “If you look at me funny, if I don’t like you, I don’t like how you are, well … I don’t play.”

Criminologists said increasing numbers of arrests typically suggest more aggressive law enforcement efforts rather than crime trends, and much disruptive behavior among juveniles is resolved in Family Court or within the school system, or otherwise fails to show up in arrest statistics. Anecdotal evidence is even stronger, however, that more and more girls are committing crimes that juvenile males are known for, such as assaults.

Teenage girls said in interviews that while name-calling or teasing and pulling hair might have long been unexceptional around some playgrounds, getting into fights is now so commonplace that it has become a rite of passage.

“It’s just what we do,” Monisha Robinson, 16, said. She has been in at least 10 fights with other female teenagers since she began school, she said. One time, she punched a classmate in the face for unwittingly sitting in her seat in school, she said. Several times, she punched her female classmates for calling her names.

“I don’t like people calling me names,” she said.

The surge in New York of assaults and other crimes among female teenagers also seems to mirror national trends of juvenile violence. In 2003, according to federal statistics, about one-guarter of juveniles arrested for aggravated assaults were girls. Ten years ago, only about 10% of juveniles arrested for aggravated assaults were females, according to the director of research for the national nonprofit Girls Incorporated, Heather Johnston-Nicholson.

“The number of girls getting into fights is definitely increasing,” Ms. Johnston-Nicholson, who is based in Indianapolis, said. “It’s not more girls than boys, but more girls than ever before.”

In New York City, one factor fueling the increase, caseworkers, social-service activists, and criminologists said, is the rising number of gang initiations among females, and the tendency for females to accept more criminal responsibility within gangs. Those gangs may not be as well-known or structured as the Bloods and Blood-ettes or the Latin Kings and Latin Queens and may more closely resemble street cliques.

Carrying drugs has always been considered one role females can play within a male-dominated gang because privacy laws restrict male police officers from frisking females. Now, however, experts said female teenagers are willing to commit more serious crimes to gain respect or status.

In March, for instance, an 18-year-old named Ashley Evans said in court papers that she provoked the widely reported shooting death of a Minnesota-born actress on the Lower East Side.

In her statement to police, Ms. Evans, who, along with a 14-year-old girl, has pleaded not guilty, said that on the January night of the slaying, the young men in her group “started commenting on how [the 14-year-old] and I didn’t fight or do anything.”

“I then initiated the next action by saying, ‘The next person I see, I’m just going to hit them,’ ” Ms. Evans said.

“The next person” was an actress named Nicole duFresne, 28, turning the corner of Clinton and Rivington streets with her fiance and two friends after a night out.

“They were extremely happy, so that made me angrier,” Ms. Evans allegedly told police.

After one of the males in the group allegedly shot and killed the actress, the female teenagers allegedly stole the woman’s cellular phone and credit cards and Ms. Evans allegedly hid the murder weapon.

Female juveniles are most often arrested and detained on charges of misdemeanor assault, felony assault, and robbery.

“Many of these young ladies will punch you like a man. They want to be just as tough as the boys,” the director of youth development services at the nonprofit Children’s Aid Society, Michael Roberts, said. One reason for the violent assaults is that female teenagers in many New York neighborhoods do not feel safe, at school or at home, and are taking security into their own hands, he said.

The attempt at self-defense can manifest itself in many primitive tactics, he said, such as gaining weight, making themselves less sexually desirable, dressing, styling their hair, or talking more like the boys do, or behaving in a loud and obnoxious way, to scare others away.

The behavior also includes fighting – and fighting other females, sometimes for the sake of fighting itself, to prove they can protect themselves, Mr. Roberts said. The most aggressive female teenagers, he said, also tend to be victims of sexual or physical abuse at home or at school. He noted that the children born during the height of the city’s crack epidemic, which shattered the lives of thousands of families and generated increased domestic abuse and other violent crime, are now teenagers.

“They say everything you learn, you learn from home,” Mr. Roberts said. “What you’re seeing now is the phenomenon of the victims becoming the victimizers.”

The identity among female teenagers is also becoming more macho and aggressive, and less stereotypically feminine, Mr. Roberts said.

Consider their most accessible role models. While girls in predominantly white neighborhoods tend to look up to comparatively wholesome teen stars, Mr. Roberts said many female teenagers in minority neighborhoods look up to pop stars such as the rapper Lil’ Kim, who was convicted of perjury in March in connection with a shooting outside a hip-hop radio station.

“There is a crisis,” Mr. Roberts said, “of people to look up to.”

Sitting on a park bench outside the Murry Bergtraum High School in Lower Manhattan one afternoon this week, Charlisha Sparks, 16, said assaults among her female friends start regularly over shoes, clothes, rumors, innuendos, lies – and sometimes for no reason at all.

Because she likes to argue, she said, she finds herself between warring factions rather than in them, so much so that she’s decided to become an attorney.

Still, she keeps her fingernails long. She must fight at least every once in a while, she said.