Metroid Database Bestiary

This heavily-armored armadillo-like creature has absorbed the Chozo artifact “Spring Ball” and taken on its powers. Arachnus has powerful forearms used for digging as well as attack. When threatened, Arachnus will roll into a ball, and his thick shell will protect him from both beam and missile attacks, but is susceptible to bomb explosives. The Spring Ball gives him the ability to jump while rolled up, allowing him to ram opponents. If the attacker persists, he will rise up counterattack with his claws and by spitting fireballs from his mouth.

Arachnus mimics an Item Sphere and so will surprise most players on first sight. His weak point is also misleading - shooting him in the head with beams or missiles will cause him to roll back into a ball. The only way to defeat him is to drop bombs near where he will land. Arachnus spits fireballs at chest-height, so you can avoid them by rolling underneath. His ball form can be avoided by either rolling underneath or jumping above. He doesn’t deal too much damage, so you can also win through attrition if you have more than 200 Energy. Defeat him to obtain the Spring Ball.

The Japanese name for this creature is “Marukara” (マルカラ), which could mean “round shell” or “from a ball”.