"Volcanic activity frees giant scorpions from the earth who wreak havoc in the rural countryside and eventually threaten Mexico City."
Richard Denning
as Hank Scott
Mara Corday
as Teresa Alvarez
Carlos Rivas
as Artur Ramos
Mario Navarro
as Juanito
Carlos Múzquiz
as Dr. Velazco
Pascual García Peña
as José de la Cruz
Fanny Schiller
as Florentina
Arturo Martínez
as Major Cosio
Pedro Galván
as Father Delgado
José Chávez
as Train conductor (uncredited)
Manuel Sánchez Navarro
as Victor Steven (uncredited)
Roberto Contreras
as Chumacho (uncredited)
Quintín Bulnes
as Lineman killed on pole (uncredited)
Isabel Vázquez
as Villager (uncredited)
Leonor Gómez
Bob Johnson
as Narrator (voice) (uncredited)
Paul Yawitz
Story
David Duncan
Screenplay
Robert Blees
Edward Ludwig
Director
Willis H. O'Brien
Visual Effects
Pete Peterson
Animation
Frank Melford
Producer
Wah Chang
Creature Design
Jack Dietz
Special Effects Supervisor
Lionel Lindon
Director of Photography
Edward Fitzgerald
Art Direction
Paul Sawtell
Original Music Composer