Kago

Kago are small insectoid creatures that coexist with each other within large hives, which are caged inside a web of hardened biomatter. They don't actively cause any damage if you leave their hives alone, but if you decide to fire, individuals are expelled to defend their homes.

In Metroid Fusion
In Sectors 2, 4, and 5 of the BSL Station, there lies a version of this creature mimicked by the X. It has a much darker purple web cage, and the Kago within now glow a bright green color. That is, if the biomatter within the cage is still a colony of Kago, as they don't come out when you fire on them. Actually, these mutated colonies are completely invincible to all weapon upgrades besides the Speed Booster and the Screw Attack. When another free-floating X merges with one of these creatures, it doubles in size, becoming a formidable and irritating obstacle to overcome.