The movie makes extensive reference to two famous Italian artists: several shots of Tara are based on Giorgio De Chirico's paintings, while the opening credits show some paintings of Antonio Ligabue's.
The short story "Tema del traidor y del héroe" (Theme of the Traitor and the Hero) by Jorge Luis Borges, that this film is based on, was set in nineteenth-century Ireland and was only 2 pages long.
The Spider's Stratagem (1970) and The Conformist (1970) were both made by Bernardo Bertolucci within a 12 or 18 month period and both were released in the same year.
The character Athos Magnani, Sr - played by Giulio Brogi - was born on 1900. The director Bernardo Bertolucci would go on to make a film set around the very same era with 1900 (1976)