During the seminars for the butterflies you can clearly see female mannequins sitting with the audience.
Due to budget restraints the blue and white bathroom tiles shown behind Evelyn as she hand washes Cynthia's underwear were created with stickers. Similarly much of the decadent wallpaper was printed from the web.
There are no men in the film at all.
The Duke of Burgundy (hamearis lucina) is a small orange and brown springtime butterfly that is found in England only with a stronghold in central-southern areas and more isolated colonies in the southern Lake District and the North York Moors.
Luis Buñuel is a big influence on Peter Stickland. Hence the name of one of the characters in the movie, Dr. Viridana, a nod to Buñuel's movie Viridiana (1961).