Phenomena

• The role of the wheelchair-bound entomologist, Professor John McGregor, was originally written for Peter Ustinov before Donald Pleasence was cast.
• New Line Cinema's US theatrical cut, retitled 'Creepers,' hacked the film down to 83 minutes from Italy's 116-minute release -- more than 30 minutes shorter, with entire sequences (including a scene explaining Jennifer's backstory with her absent mother) removed entirely.
• McGregor's chimp assistant, Inga, was played by a real chimpanzee named Tanga who was genuinely dangerous on set: she bit off part of Jennifer Connelly's finger during filming, and in the climactic attack it's actually Tanga's own hand wielding the (blunted) straight razor -- it scarred co-star Daria Nicolodi for real. No puppet stand-in was used for that shot.
• Argento got the idea for the film after hearing a news report about criminal investigators using insect activity on a corpse to help solve a murder -- the same real forensic-entomology principle behind the corpse-seeking fly (a Sarcophaga, or flesh fly, a genus actually used in real death investigations) that McGregor gives Jennifer.
• Exteriors were shot on location in Switzerland -- including Urnäsch and the Thur waterfalls -- with Zurich's Rietberg Museum standing in for the girls' school, while interior sets were built at the De Paolis studio in Rome.

Jennifer's insect-whispering isn't supernatural at all but an extreme manifestation of her sleepwalking psychosis. Her somnambulism and her 'communication' with insects both stem from the same dissociative fugue state, meaning she's unconsciously tracking the killer herself and the bugs are just her mind's way of processing what she already senses.

McGregor's chimp, Inga, is deliberately positioned as Argento's commentary on the giallo killer's animalistic nature. The chimp's final razor rampage mirrors the human killer's methodology, suggesting the real monster isn't the deformed son locked away but the learned violence that even an animal absorbs from proximity to human brutality.

The Swiss academy functions as a thinly veiled asylum, and Jennifer's 'gift' is actually her subconscious recognizing that the killer is connected to a psychiatric case she encountered during earlier treatment she's repressed, with the insects serving as traumatic memory fragments trying to surface.

A sleepwalking American teen lands at a Swiss academy for girls just as a killer starts butchering students. Jennifer Corvino doesn't fit in, but she has a strange gift: insects respond to her. A wheelchair-bound entomologist and his chimpanzee assistant recognize her ability and put a fly with a taste for corpses on the case. What follows involves a deformed child locked away, a razor-wielding killer, and a chimp going absolutely feral with a straight razor. Argento's most unhinged giallo, and that's saying something.