An Acherontia styx pupa found in the soft palate of a murder victim is a vital clue in the thriller novel The Silence of the Lambs ; in the movie version , however , while the script still refers to styx , the species used is Acherontia atropos . An Acherontia styx pupa found in the soft palate of a murder victim is a vital clue in the thriller novel The Silence of the Lambs . In the movie version , however , while the script still refers to styx , the species depicted is Acherontia atropos .