A Beetle lair is a type of hive present in Metroid Prime, in the Root Cave room of the Tallon Overworld. It appears to be a large anthill-like compound that exists at the very bottom of the shaft. When Samus approaches it, it will cause numerous Beetles to appear and attack. It appears to be giving off steam. This is the only one present in the game, so it is unknown how beetles found their way to other parts of the planet, although these hives could merely be deeper underground.
"Analysis indicates incubating life-forms below the surface."