this is a diagram about the sand worms found on Arrakis they are very deadly. in the story the Fremen use there teeth as knifes, and also for transportation. In the story duke Leto and Pual with other military commanders, went on a trip to see a harvester and its procedure to gain spice. the duke ends up spotting a sand worm and informs the harvesters at work. They don't have a ship to save them so the duke ends up having to pick them up and carry them back to the castle.