Silence of the Lambs is a death's head hawkmoth not a butterfly.
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One of the big problems I ran into with scavenger hunts/trivia games is you have to make them easy to figure out even if someone isn't a huge horror fan... so unless your friends are super fans, have to make it easy or end up with most of them claiming it's too hard or giving up due to frustration.
SCAVENGER HUNT SUGGESTIONS
Simple clue list. I did several variations for scavenger hunts - always photo hunts since everyone should have a cell phone with an excellent camera (or allow folks to either go it alone or work as a team if there are couples). I made either a large sign of the rules if it was a simple hunt or a list of X number with simple clues for each answer.
So one hunt I did was 13 thirteens, and it's soooo much easier to come up with fun stuff for this for a photo hunt (might save the movie stuff for the trivia questions?). There were going to be things in plain sight that were either the word/number 13 or consisted of 13 like objects. I had 13 clown masks (a face painting station), 13 spiders climbing up the kitchen cabinets, 13 bats (hung in a garland at the doorway/entrance), an actual photo of myself and husband holding up (combined) 13 fingers in a photo arrangement with other regular framed photos, a 13 hour clock... I even made sure to mention on the signage explaining the rules that the SIGN was the first thirteen so make sure to take a photo!!
If you are doing a horror movie scavenger hunt, it would probably be easy to limit to 13 horror movies that are VERY well known even for the ones that aren't huge fans. You can either use a simple or easy clue without stating the name or just state the name and then do some nice vignettes using ideas like what you've come up with.
But if you want to do some movie stuff for a scavenger hunt:
IT: red balloon tied to a Welcome to Derry, Maine" sign. CLUE: Pennywise wants to play. We all float down here. What is IT?
Blair Witch: the little stick figures (make a BUNCH of them) and have an old camcorder set up. Bonus points if you can make a simple figure standing in a corner with their back facing out (can make something like this pretty easy out out of old clothing and might luck out if you find stuff in thrift stores). CLUE: Witches be crazy and sometimes... they be real. This little project turned out to be more than they bargained for.
Scream: If you have a ghostface mask and an old school wireless phone... that's really all you need. I would change it up by maybe taking a PHOTO of this and framing it and hanging on the wall in a spot where you typically have stuff hanging on the wall anyway. Make it a BIT harder to find the stuff but still out in plain sight.

CLUE: Do you like scary movies? This movie gave a bloodcurdling new voice to the slasher genre in the 1990s!
Seven: A nice way to hide this one since it would be super easy to just make a list of the seven deadly sins: make a large grocery list type of paper in red marker/ink (bonus points if you use a bloody spatter font) mark out a few of them, end it with "what's in the box?" and put it with a magnet on your fridge.

CLUE: Deadly sins, a serial killer, and Gwenyth Paltrow's head in a box... what's not to like?
Sleepy Hollow (the one with Christina Ricci and Johnny Depp): One of the bird/cage spinny string toys, a headless horseman (toy/picture), and if it was me, a nicely framed photo of Christopher Walken because he's awesome. CLUE: Don't lose your head over this Sleeper hit based on an old folk tale!
I Know What You Did Last Summer: dark colored rain coat and a hook, hanging near the front door? Hang a seascape near it and write in bloody letters across it "I know what you did..." (again, may be able to find stuff at thrift stores). It was dark and not so rainy night when a carload of teens drove headfirst into HORROR!
Silence of the Lambs: a basket with a stuffed poodle toy dog OR lamb, a can of fava beans, and some lotion.

CLUE: Are the lambs still crying, Clarice?