I watched The Silence of the Lambs a couple of years ago. Yesterday I saw its poster online. It has a girl (which I am thinking is Clarice Starling, if I am not wrong) and a moth (or maybe a butterfly) on her mouth. I am just wondering, what does it mean? How is it related to the movie?
This award-winning poster art conveys many of the movie's themes and plot points:
Clarice's skin is pale (in stark contrast to the darkness surrounding her) and blue like a corpse while her blue eyes had turned red, representing the film's themes of death, danger and virtue confronted with a malvolent influence (Lecter's eyes are red in the books, and another poster featuring his face employed a similar color scheme).
The moth with the skull pattern is a death's-head hawkmoth that's found in one of the bodies. Buffalo Bill inserts a moth's cocoon to the mouth of one of his female victims. Moths represent change in the movie, and other than explicitly representing Buffalo Bill's desire to change, it could certainly be argued that Clarice also transforms during the investigation.
The skull on the moth actually replicates In Voluptas Mors [Warning: Nudity], a photo conceived by Salvador Dali of seven naked women[*] that form a skull. This not only suggests the lewd nature of the crimes seen in the movie, which involve female bodies, but also the complexity involved (Lecter is an extremely cultured man and a skilled painter).
The moth also covers Clarice's mouth to allude to that titular Silence she so desperately needs.
[*] [As a point of interest: Before the plot starts in both book and movie, Buffalo Bill as a serial killer (since he's responsible for other, unrelated murders) had already kidnapped 5 women, skinned them and dumped their naked bodies in rivers. Later on, Starling would attend the autopsy of his 6th victim, and eventually save Catherine - which would've been Bill's 7th victim.]