Hemus is a genus of spider crab in the family Majidae. The carapace of the longnose spider crab is nearly circular in outline. The Agulhas spider crab may grow to . The longnose spider crab is a scavenger and detrivore. Arthropods range in size from the microscopic crustacean "Stygotantulus" up to the Japanese spider crab. Maja capensis, the Agulhas spider crab, is a species of crab in the family Majidae. Marine arthropods range in size from the microscopic crustacean "Stygotantulus" to the Japanese spider crab. Libinia dubia, the longnose spider crab, is a species of crab in the family Epialtidae. The legs can be very long in some species, leading to the name "spider crab". The Japanese spider crab is an omnivore, consuming both plant matter and animals. The great spider crab can moult and get rid of their outer shell/skin. Among crabs only the Japanese spider crab ("Macrocheira kaempferi") can weigh more.