How do you say black monkey in french?

Bete Noire ( Black Beast) would be the equivalent phrase. actually Black monkey would be Le singe ( pronounced Sange) Noir. Planet of the Apes was known in its French original as Planet des Singes- no translation needed ( Planet of ( the implied) Apes). It was the only Science Fiction novel by Pierre Boulle better known for the Bridge on the River Kwai. ( War novel).