Sandworms are fictional creatures from Frank Herbert's science-fiction novel Dune. Scientific name Geonemotodium arraknis (also Shaihuludata gigantica), they are known locally as Shai-Hulud by the Fremen. The Fremen believe that the actions of Shai-hulud are directly the actions of God. He is the Great Maker, The Worm who is God; other names for them include the "Old Man of the Desert," "Old Father Eternity," and "Grandfather of the Desert."

"Bless the Maker and all His Works; Bless the coming and going of Him; May His passing cleanse the world!" as the Fremen prayer goes.

Shai-Hulud are enormous animals, growing up to hundreds of meters in length (400 metres have been recorded), burrows beneath the sands of the desert planet Arrakis. They begin their lives as sandtrout sometimes called "Little Makers". These small creatures have the habit of encapsulating water thus causing the desert to be dry. At some point in their lifecycle they switch from being individual creatures and form a kind of colonial organism. Over time this being metamorphoses into the giant sandworm. They have very long lifespans, in the thousands of years and little can harm them. Anything producing heat, such as a laser, is simply absorbed by their body, however, Water is poisonous to Shai-Hulud. All attempts to transplant these massive beasts to another planet have failed. It is suggested sandworms gain the energy to sustain themselves from the ingestion of 'sand plankton'. Exactly where sand-dwelling microorganisms would gain energy from is unclear - it is obvious they do not photosynthesise.

Shai-Hulud produce, as metabolic byproducts, three important substances: oxygen which is expelled from their trailing body, sand from the constant consumption and excretion of rock, and the extremely valuable spice melange which is released along with water as a waste product of sandtrout. This mixture is known as the pre-spice mass, and will generate carbon dioxide and other gases. The exact chemical processes remain unclear; what is known is that in open desert, if one smells the overwhelming fragrance of cinnamon (melange's odor), one may be on the top of a pre-spice mass. The slightest vibration may cause the gases trapped beneath the sand to erupt, killing you and the thousands of sandtrout which have gathered to form the pre-spice mass. The resulting explosion scatters the raw spice all over the sand which dries in the sun. This is the substance the harvesters are seeking; Melange. Incidentally, this is also the catalyst in the life cycle of the sandworm, whereby the surviving sandtrout merge to form small worms, which grow and develop into Shai-Hulud.

A highly concentrated form of melange can also be obtained by drowning a sandworm in water. This produces spice essence, or the "Water of Life," a liquid exhalation which is highly toxic. It is used by both the Fremen and the Bene Gesserit in the Spice Agony, the method by which Reverend Mothers are made.

Shai-Hulud are very dangerous, as they will aggressively attack anything that produces rhythmic vibrations on the surface of the sands. The Fremen have learned by observing the other wildlife of Arakis to "Walk without rhythm" thus failing to attract a worm. The Fremen have developed such a close relationship with Shai-Hulud that they can actually "Ride the Worm". The Fremen do this by first attracting a worm with a device called a Thumper. When the worm comes they maneuver along side of it and using a "Maker Hook" they open the space between one of the worms segments exposing the softer tissue beneath. This causes the worm to rotate this part of his body as far away from the irritating sand as possible, thus lifting the Fremen up onto its back. The Fremen use this technique to travel hundreds of miles at a time. It is also part of the Fremen "Coming of Age" ceremony.

What does the sandworms eat?

There is a lesser known joke among the ecologists in the imperium.

Question: What do the sandworms of Dune eat?

Answer: Humans.

The answer, though technically correct, is ecologically invalid as sandworms do not consume enough humans to be able to sustain themselves. The mystery of how the sandworms of Dune sustain itself is one of the greatest mystery of the imperium.

Worm specimens we've examined lead us to suspect complicated chemical interchanges within them. We find traces of hydrochloric acid in the ducts, more complicated acid forms elsewhere. - Liet Kynes (Dune, in the Ornithopter with Duke Leto)

Derivative works

This concept of sandworms has been used for other fictional works, for example the film Beetlejuice.