A Metroid Cocoon is a breeding hive for Infant Tallon Metroids in Metroid Prime 2: Echoes. They are only seen in Biostorage Station, and hang on ceilings. According to the scan, they are used to transport the Metroids. They are very resilient to attack, which somewhat contradicts the statement in their scan (although the scan only says they have no armour or shielding; they may just have a very tough outer layer). It is unknown if the cocoon is a natural hive for the Metroids, or if it has been engineered to transport the species by the Pirates; the latter suggestion seems to be the most likely, as it is hinted in the scan below.
Morphology: Metroid Cocoon. Storage chamber for young Tallon Metroids. Biomass to support Tallon Metroid infants. Lacks armor or shielding.
The Space Pirates transport young Tallon Metroids in an organic "cocoon" designed to sustain the small creatures. Each cocoon can support numerous infants for several cycles. The creatures are normally content to remain in the cocoon, but will emerge when they detect the presence of Phazon.
- In Metroid Prime 3: Corruption, several unknown pulsating cocoons can be found near Phazon-corrupted Metroid Eggs on planet Phaaze. Because these cocoons are in close proximity to Metroids, these may also contain the creatures at a certain stage of development.