Behind the scenes: Acromantula

The Harry Potter series is not without its terrifying moments, complete with a giant, murderous serpent. But what’s more terrifying than a giant, murderous serpent? If you’re Ron Weasley, that would have to be a giant, murderous spider…

Aragog emerging from his nest
Harry Potter and the Chamber of Secrets

Extracted from Harry Potter: The Creature Vault by Jody Revenson

Acromantula are a species of spider found in the world of Harry Potter that can grow to the size of an elephant. One of their unique features is their ability to converse with humans.


Aragog, the leader of a colony of Acromantula, was brought to Hogwarts by Rubeus Hagrid when he was a student, fifty years before the events of Harry Potter and the Chamber of Secrets. Harry and Ron encounter this beloved pet of Hagrid’s during their second year at Hogwarts, as they try to uncover the truth behind the identity of the heir of Slytherin. Sadly, Aragog passes away from old age during the events of Harry Potter and the Half-Blood Prince.

When the designers read the script for Harry Potter and the Chamber of Secrets and discovered that a spider with an eighteen-foot leg span would be required, their obvious initial thought was that the creature would be computer-generated. Upon further consideration, however, it was decided that Aragog’s myriad offspring would be digital, but not Aragog. The creature shop realised that constructing the Acromantula would be more economical than CGI, and it would also allow them to make Aragog walk and talk on a life-size scale.

Aragog was crafted using an Aquatronic system that utilises cables pumped with water instead of the oil-based system used in hydraulics. Aquatronics create a smoother, more graceful movement. Being the size of an elephant, Aragog needed to move with a similar unhurried elegance. The slow movements also imitated the quiet, menacing way that spiders creep around. The spider’s back legs were manipulated by puppeteers while his forelegs were mechanical. These mechanical legs were operated by a motion-control device called a waldo that reproduces movements made by a controller. Then, Aragog was fitted onto a system that resembled a seesaw, with a counterweight on one end. Placed into a depression in the soundstage, when Aragog was tipped up, he literally walked forward.

A voice-activated system was installed in Aragog’s head so that his mouth would move in synchronisation to a broadcast recording of actor Julian Glover’s voice as the character. This allowed Daniel Radcliffe (Harry Potter) and Rupert Grint (Ron Weasley) to act in real time with the creature.

Aragog was completely redesigned for Harry Potter and the Half- Blood Prince to show his age. The creature was cast in a urethane that allowed light through it in order to emulate the translucent glow of an actual dead spider. The same ‘hair’ materials were used for both Aragog versions in Chamber of Secrets and Half-Blood Prince, including broom hairs for the finer ones and feathers with a coating of fluff and Lurex for the bigger, hairier ones. The hairs were inserted one at a time.

The script for Half-Blood Prince called for Aragog to be slid into a grave on a hill, so the designers knew that the Acromantula needed to be much heavier than the original in order to give the correct heft of a huge, upside-down dead spider. The creature was such a beloved character that the design crew wore black armbands while the spider’s final scene was filmed.

Aragog's nest in the Forbidden Forest
Harry Potter and the Chamber of Secrets

Harry Potter: The Creature Vault book cover

Extracted from
'Harry Potter: The Creature Vault'