Splinter Cocoons are protective houses for the Splinter species in Metroid Prime 2: Echoes for the GameCube. They are only found at the Industrial Site and once the Splinters emerge from the cocoons the cocoons will remain destroyed for the rest of the game, making them a one-time-only scan.
"Splinters will enter their protective cocoons when tired or sated. The cocoon is durable, but can be destroyed by weapons fire. Destroying a cocoon will kill the Spinter inside:when this occurs, the dying Splinter will let out a shriek that will alert all nearby Splinters in hybernation. This will drive them into a battle frenzy as a defense mechanism."