Hello from the sewers... hello from the cracks in the sidewalks of N.Y.C., and from the ants that dwell in these cracks and feed on the dried blood that has settled into the cracks.

With that grotesque greeting, hand-printed in compulsively neat capital letters, a man who has killed five people in eleven months began a rambling and ghoulish letter to New York Daily News Columnist Jimmy Breslin. The writer, known by his mysterious signature Son of Sam, said he was "hungry" for more killings.

True to his word, the murderer struck again last week, creeping up behind a couple parked on a tree-shaded street near a disco-théque in the borough of Queens and firing four shots from his .44-caliber Charter Arms "Bulldog." Though Judy Placido, 17, and Salvatore Lupo, 20, his tenth and eleventh victims, were wounded, both miraculously survived. But the latest, and most publicized, attack tightened the grip of fear on neighborhoods in Queens and in The Bronx, where the bizarre, psychopathic killer has chosen his targets.

Despite an investigation that has grown to include more than 50 detectives, police at week's end had no solid clues to the identity of the so-called .44 Caliber Killer  only reports from a few witnesses that he is a dark-haired white man in his late 20s or early 30s who fires his revolver while holding it in both hands, police style. Hunting for clues, experts have thoroughly analyzed his note to Breslin, plus another letter left at a murder scene filled with such violent and repulsive language that it has not been released to the public. Amid the vilifications contained in the second letter are hints that the writer is reasonably well educated and may have attended a Roman Catholic school.

Waiting for him to strike again, New Yorkers are grimly recalling the Boston Strangler and Jack the Ripper. Like those classic murderers, the Son of Sam seems intent on killing women. Most of his attacks have been on long haired brunettes, many of them sitting in parked cars at night with their boy friends. Two of the male victims were wearing shoulder-length brown hair, and police think that the killer may have mistaken them for females.

Terrified parents in the area are now insisting that their daughters wear their long hair up, bleach it, or have their dates at home. Some girls have decided not to date until the killer is caught, and others are adopting unusual evening wear: loose sweaters and large caps to disguise themselves as males. "I'm scared," said one Queens girl. "I used to kiss my boyfriend in front of the house, Now I run in."

Police have checked mental hospital records, tracked dozens of suspects for days, investigated many false confessions, and even talked to a few nervous wives who suspected they were married to the killer  all to no avail. Law authorities have also had witnesses hypnotized to aid their recall of details, and have vainly asked astrologers to predict the next killing just on the chance that the murderer is himself a follower of astrology.