Reos (リオ, Rio) are enemies from the Metroid series.
Reos (also referred to as "Rios" in early Metroid games) are inhabitants of Zebes who resemble flies, and are among the many hostile creatures that will attack Samus Aran. They possess sharp claws and can be resilient, especially posing a serious threat in large groups. They can usually be found flying high in the air, and then they attack by swooping down low when Samus approaches them. In Other M, Reos are seen appearing from nests of biomass called Fly Pods; they can latch onto Samus, forcing her to shake them off.
Reos appear as enemies, based on their appearance in Other M. They remain stationary in the air and attack by swooping down on nearby players, behaving similarly to their appearances in 2D Metroid games.