They are small boys, 11, 12 and 13 years old, still blushing when asked about their girlfriends, still chasing ice cream trucks when they have the money. But when guns and homemade bombs explode on the streets here, they stand on the sidewalks with the older boys, hurling rocks and bottles at every passing white motorist. They cheer when they hit a windshield and glass shatters.

People in the grim, sprawling black ghetto here call them "the little shorties." They are troops in the brutal streets wars of Miami, only part of the baleful story this summer in this smoldering and torn town.

Alex Moore, 13, takes small bites out of a hot sausage he has cajoled a reporter into buying from the ice cream truck. He talks about being on the streets of Liberty City, the site of two bloody riots in two months, about throwing rocks at whites -- "crackers" -- as they drove by.

"I hit a cracker cab, then a cracker came down in a van. I hit him, too."

Why? He smiles, sighs, gives the visitor a look of mock exasperation.

Was he afraid out there with the fires and the police and the older boys exchanging volleys of gunfire?

His smooth brown face hardens. "When they shoot me," he says, "they better had kill me."

In the slums here, where in some neighborhoods eight of every 10 young black men are out of work, where one teeming apartment complex has been so overrun with trash and filth that everyone calls it "Germ City," they say again and again there is no hope.

No hope. And, as a result now, no fear.

"You're not talking about a handful of kids," said David Alexander, the editor of the Miami Courier, a black weekly in Liberty City and one of the few community spokesmen on the streets the night of the most recent violence in Miami. "You are talking about hundreds, hundreds who have no fear."

Dade County Manager M. R. Stierheim calls the shootings, the bombings and the hate-filled racial talk from both blacks and whites in metropolitan Miami a form of "social disintergration." In the bombed-out black ghetto here, they call it the rebellion.

"We have tried to follow the system, but we ain't getting no feedback," Homer Brennan, 27, a Vietnam veteran who came back from the war to the housing projects and no job, told white Miami leaders at a forum last week. "you sent me over there to shoot Vietnamese, and then they come here and live better than I do. You think I'm not going to throw a rock at you?You got to be mad.

"You trained me to be violent. You programmed me to be violent," he shouted as middle-aged black men and women in the audience applauded. "Seems like the only way I can talk to you is through violence." Later, he told a reporter, in an almost offhand way, "you know, a lot of us ain't scared of dying no more."

Preston Marshall was a college student and on the streets here in 1968 when there was a smaller riot in one of the same areas that burned last May. Now he is the director of the Teacher Corps, and he walks the streets again, trying to find some channel, some way, to get through to the "litle shorties," the embittered teen-agers and the angry young men out there.

"In the '60s, we were just young foolish and trying to express ourselves," he said. "We were still trying to pull the race together to understand that black was beautiful."

But it is different now, he says, far more bitter, more destructive. "They are saying if whatever they do messes things up, then good. There's some ornery little guys who say all they want is to see a cracker and hit him in the head with a brick."

The small coterie of black government and elected officials has been diminished by a string of recenet corruption indictments and convictions. The civic types who remain are fighting for jobs and government money for the slums, but they have failed to exert any leadership in the ghettos themselves.

Miami Urban League President T. Willard Fair was asked whom poor black youth listen to. "There's no monolithic voice that talks to them," he said. "You listen to the person who survives. So it becomes 'Droopy' who always has some pot to smoke. It becomes 'Sister' who always has money to go to the store."

On a recent afternoon, as teen-agers at the James E. Scott public housing complex chased reporters from the project, one yelled at the retreating journalists: "And one more thing: tell those old [he drew out the word for emphasis] black leaders to stop jumping in front of the television cameras giving interviews because they do not speak for us."

Miami 1980. Riot without rhetoric or leaders.

Searching for the causes is a lot easier than finding solutions. And right now this city is floundering and does not have any good answers.

Blacks all over Miami, in the slums, in the little jewel-box houses in the posh section of Coconut Grove where a few members of the small black middle class live, can still remember the revulsion and rage they felt on Saturday, May 17. When they turned on radios they learned that an all-white jury in Tampa had acquitted four white Dade County policemen in the beating death of Arthur McDuffie, a black insurance salesman.

(On Monday, a fifth white former policeman was indicted on federal charges of helping cover up details of McDuffie's death.)

The acquittal of the four policemen was, blacks say, the cruelest insult in a string of police indignities -- the suspended sentence given to a white Florida highway patrolman who sexually molested an 11-year-old black girl; the minor "negligence" indictment of an off-duty police officer guarding a warehouse who shot a 21-year-old black man in the back of the neck after he stopped to relieve himself by the building's wall.

The acquittal in the McDuffie case sparked three days of bloody rioting. Eighteen persons were killed and more than $100 million in damage was done in 52 square miles of Miami.

One hears little in the way of regret from adults or teen-agers, from the well-off or the poor, about what happened during those days of rage in May.

"What do you think would happen in this community if black folk had just sat back?" asked Clyde Pettaway, assistant director of the James E. Scott Community Association, a federally funded service program. "We would be the living dead. We would have been in human bondage again. White folks act like they can't understand that."

But then came the second outbreak of the summer. Again the trigger was and incident involving white Dade County police officers. On the afternoon of July 15, a crowd gathered as police attempted to arrest three young black men trying to rob a white motorist.

There was a scuffle; a shot was fired, lodging in the shoulder of one policeman. The suspects fled into the cheering crowd.

Street wars in black Miami consumed the next two nights. But this time older blacks did not participate -- it was the "little shorties" and the teen-agers and men in their early 20s who threw the rocks and bottles, laid ambushes for police and blasted away with revolvers and shotguns.

Older blacks publicly decried the violence; some even met with police to lay strategy for stopping it.

"I do think they went a bit to far," said Pettaway. "Any time you burn a health center that is serving the total JAMES E. Scott community, man, you wonder what is sacred."

The tentative alliance lasted only a few days. Black community spokesmen reacted angrily after white leaders decried the "thugs" and "hoodlums" who perpetrated the July violence.

The was between blacks and police continues. Officers were outraged earlier this month when their superiors restrained them from aggressive actions in response to the renewed rioting.Whenever police officers go into the slums now there is a palpable rising of blood pressure.

Caravans of helmeted, flak-jacketed, shotgun-toting police swarmed in and out of the James E. Scott housing projects a few days after the latest disorders, in an operation similar to one employed a decade ago by the U.S. 1st Air Cavalry Division in the highlands of South Vietnam. There it was called "cordon and search" and was aimed at rooting out the Viet Cong infrastructure.

Here it had no name, but its object, said Dade County Assistant Safety Director Robert Dempsey, was to lock up the "agitators" and the "hard core." Pulling out old arrest warrants and acting, he said, on anonymous tips, teams of up to 25 policemen swept the projects making arrests.

One of the first to be arrested, on an old forgery warrant, was Vietnam veteran Homer Brennan. At the time of his arrest he was helping poverty program workers with a job sign-up drive being conducted from tables in his front yard.

Dempsey, who supervised the police during disorders here in July, said the police have become the symbol for all the frustrations in black Miami, but the problems go deeper.

Few here disagree.

In the ghettos, they scoff at the federal social programs of the '60s and '70s, regarding them as snarls of red tape and broken promises. Ghetto residents regard these last two decades of the Great Society and affirmative action as years of retrogression and decline.

Blacks from Georgia and the Carolinas have migrated to Miami since the turn of the century, working in large numbers for the hotels and as porters and dining car waiters for the Florida East Coast Railroad, in the days when rail was the dominant mode of travel to the beach resorts.

The climate was good, and Miami was considered to have a less harsh form of segregation.

In Colored Town, later called Over-town, near downtown Miami, there was overcrowding and substandard housing, but there also was a vibrant commercial strip of nightclubs, restaurants, drug stores and hotels where Lena Horne, Louis Armstrong and Nat (King) Cole would stay and perform after engagements in whites-only Miami Beach.

In the 1960s, the forces of urban renewal and highway construction wrecked that community, and blacks have not been able to recreate any viable commercial strip in Liberty City to the north, where many moved. The frail black economy here now consists of little dry cleaning establishments, beer joints and funeral homes.

While there are almost no jobs within the black community, there are increasingly fewer jobs outside it. Waves of refugees fleeing Fidel Catro's Cuba make up more than a third of the population here, outnumbering blacks by more than 2 to 1. Whites comprise slightly less than half the population of Dad County.

Now the Cubans hold the hotel jobs on Miami Beach that blacks held until a command of Spanish became a requirement for employment. Over the years the Cubans have built up a flourishing economy of restaurants and shops in Little Havana. They are the object of resentment and envy in black Miami.

On the streets in the ghetto, in the projects, people say unemployment and inflation are killing them. The unemployment rate for all blacks runs from about 15 to 17 percent, more than three times the average for Dade County. Nearly half the black youths in Dade County are out of work; in some neighborhoods the rate rises to 85 percent, accoring to a report county manager Stierheim made to a White House task force.

One thing that immediately strikes a visitor is how poor the poor appear to be. Rarely do you see the Adidas sneakers, hand-held radios and 10-speed bicycles that are so often in evidence in Washington's central-city slums.

Children in Miami wear cheap slacks cut off about the knees and the kind of inexpensive black high-top sneakers that kids wore 20 or 30 years ago.

And, there was the dismaying whispering conversation of 13-year-old Alex Moore and a group of his friends one afternoon as they played among the weeds of the projects. The talk was of dinner. What became clear was that on that night, like others, there would not be food on the table in every apartment. So, among themselves, the boys first surveyed to find out whose mother was preparing dinner, then put bids in for invitations. That done, the talk was about what might be served. "Pork and beans!" one youngster bellowed. They all laughed.

There has been a fury over the summer jobs for youth program, which has grown fitfully after each upheaval here but is still regarded as inadequate.

A woman out of work and with three children here gets a welfare check of $230 a month -- more than in other southern cities such as Atlanta and New Orleans, but about $119 less than in Washington and $257 less than in Los Angeles.

"When they're talking about working, they're not playing," said Pettaway of the James E. Scott Community Association. "They need the job. Their family needs the job. What we're talking about is survival."

Dade County has put in an urgent request for more federal funds to modernize the long-neglected government housing projects, acres of one-and two-story plain concrete hulks, painted tan and light green. Squadroons of flies swarm around overflowing garbage bins. There is little in the form of recreation during the day, no air conditioning to cool the hot nights.

Black Miami is isolated. Walls of superhighway separate it from prosperous white Miami, where Latin tourists peel $100 notes from rolls of bills to make purchases at the expensive Omni Hotel and shoppers visit the Rolls Royce showroom on Biscayne Boulevard.

A social worker who spent a year working at the Scott projects said she was alarmed to learn that there were several 18-year-olds who had grown up in Liberty City but never seen the beach.

"Integration of black and white communities continues to be a legal concept rather than a practical reality," County Manager Stierheim said in his report.

Whither Miami?

Newspapaer columists here, and white and Cuban-American leaders, are increasingly expressing anger and exasperation at the continuing disorders. They call on black officials to act to quell the trouble while a program for rebuilding is mapped out.

Carolyn Jones, a community activist who travels the streets of the slums, complains like others about the favorable treatment accorded Cubans in seeking jobs. But she believes the solution must go beyond changing that.

Something must be done about the shattered family here, where one of every two households is a single-parent home. Somehow, she said, blacks must become less dependent on federal money for their efforts. She believes there is an example for blacks in Little Havana, where Cuban families pool resources and pull together to build businesses.

Stierheim said in his report that he believed it was essential that a solid economic base be created to give blacks a stake in Miami.

Pettaway believes any battle for black Miami must go even further than that.

"It's kind of at the point where white folks are going to have to look at themselves, be honest with themselves, say how racist they are," he said. "If they continue to keep that inborn racism within themselves . . . we will keep right on until we selfdestruct our own country."