Classic 1950s science fiction movie, released in 1954. It was directed by Gordon Douglas and written by Russell S. Hughes and Ted Sherdeman

The stars included James Arness as FBI Agent Robert Graham, James Whitmore as Sgt. Ben Peterson, Edmund Gwenn as Dr. Harold Medford, and Joan Weldon as Dr. Pat Medford. A number of actors played small or uncredited roles, but one notable role went to Fess Parker as Alan Crotty, a pilot temporarily committed to a mental ward after seeing a UFO

The plot: New Mexico State Police Sgt. Ben Peterson and his partner locate a catatonic little girl wandering the desert near Alamogordo. They also discover a wrecked vacation trailer and a demolished general store. Peterson's partner disappears while investigating a loud pulsating noise, and a large amount of fomic acid is found in the shopkeeper's body. 

The investigation soon expands to include FBI Special Agent Robert Graham and two entomologists from the Department of Agriculture, Dr. Harold Medford and his daughter Pat. Medford exposes the little girl to the fomic acid fumes and she startles awake, screaming "THEM!" Soon after this, Pat encounters a gigantic ant -- the police officers manage to kill it, and Dr. Medford tells them he thinks atomic bomb tests have mutated a colony of ants into giant monsters. 

A search by helicopter soon finds a colossal ant nest, and cyanide gas bombs are tossed inside. A search for survivors inside the nest brings up evidence that two ant queens had recently hatched and escaped to establish new colonies. 

After a nest is discovered aboard a ravaged freighter, the Navy sinks the ship. But there's still another queen to be accounted for. When a new nest is discovered in the storm drains underneath Los Angeles, a full military operation will be necessary to clear out the ants before they emerge and destroy the city. 

The film's special effects are a bit primitive, but the acting is first-rate, the dialogue is outstanding, and the story is intelligent and genuinely suspenseful. There's a strong sense of mystery throughout, leavened with plenty of action. It's a great example of 1950s creature feature science fiction.

Best trivia: The movie was responsible for two of the actors getting primo roles on TV series. Walt Disney watched the film to see if James Arness would work for his planned "Davy Crockett" series, but liked Fess Parker's performance as an inmate at a mental ward better. Meanwhile, John Wayne watched the movie and recommended Arness for the role of Marshal Matt Dillon on "Gunsmoke."