Floral biology of the Horse's Arse Arum Lily

The proper English name of the depicted species is Dead Horse Arum Lily, but a direct translation from German or French (the species occurs on Corsica, Sardinia and the Baleares) is Horse's Arse Arum Lily. You can't see it from these pictures, but the flower, when seen from the front, looks truly like a horse's arse. It does, however, also stink like a dead horse.