Lecter converses with Starling on the phone at the end of The Silence of the Lambs. The black speck near the left side of Lecter's forehead is the infamous fly (click image to enlarge).
To determine why it is that Silence of the Lambs director Jonathan Demme, decided to leave the 'fly' in the final scene (the insect coincidentally alights on the side of Anthony Hopkins' head at the end of the movie - see the screen capture above), instead of re-shooting the scene without the fly present, it is useful to consult the Dictionary of Symbols:
"Their ceaseless buzzing, whirling around and stinging make flies unbearable. They breed from corruption and decay, carry the germs of the foulest diseases and breach all defences against them. They symbolize a ceaseless quest. It was in this sense that an ancient Syrian deity, Beelzebub, whose name meant 'Lord of the Flies', became 'Prince of Demons'."[a]
As stated back in part 22 of this analysis, the name Hannibal suggests Baal, who is sometimes seen as a demon in Christianity. Christian writings referred to Ba'al Zebûb as a demon or devil, often interchanged with Beelzebub.
a. Dictionary of Symbols. Ed. Jean Chevalier and Alain Gheerbrant, Trans. John Buchanan-Brown. London: Penguin Group, 1996. pp. 396, 397.
