Kihunter

Kihunters (or Keyhunters ) are a race of insect-like beings that have joined with the Zebesian Space Pirates. They appear in Super Metroid, Metroid Fusion and Metroid: Other M.

History
Kihunters are allies of Space Pirates and hail from another galactic system; according to Super Metroid ' s manual, they are pirates from another galaxy who travelled to Zebes to assist in the reconstruction of the planet's Pirate bases. Whether this means they are Space Pirates (as a species) or merely in profession is unknown. In Other M, the Kihunters are shown to possess a very insect-like organization/hierarchy within their race, with a King Kihunter seemingly leading them. Their method(s) for space travel is unknown.

The only planet that they are seen inhabiting in the Metroid series is Zebes. They have wings, allowing them to fly, and can spit acid from their mouth, though they mainly charge their opponents while swiping at them with their claws. If they lose their wings, they will only spit acid and travel by hopping.

In Super Metroid, they can be found in large numbers in several areas on Zebes, with the creatures' colors appearing to adapt and blend in with the surrounding (and sometimes harsh) environment. There are three different colored Kihunters, and the weakest to the strongest variant are as follows: green for Crateria and Brinstar, dark green for the Wrecked Ship and red for Lower Norfair.

Kihunters also appear in Metroid: Other M in their first 3D appearances. The Kihunters here are a shiny blue-green color and, for reasons unknown, now possess six limbs instead of four; this is the adult form of a Kihunter. They appear in the Biosphere of the Bottle Ship; like most creatures within the ship, Kihunters were being experimented as bioweapons by corrupt factions within the Galactic Federation. Early in the game, Samus is forced to go through their nest and must defeat their King. In this game, Samus can remove their wings by firing a Power Beam Charged Shot or rip them off using the Overblast technique. When they are unable to fly, Kihunters will slowly approach Samus and suddenly jump at her in an attempt to cling to her. If successful, they will sacrifice themselves by exploding (an ability never before seen), causing considerable damage to Samus. They are often found near Zeros, their larval stage, and some Zeros may quickly molt to become Kihunters in a matter of seconds. Samus indicates surprise at encountering them, wondering about the return of the "beelike creatures."

In Metroid Fusion, Kihunters have been infected and mimicked by X Parasites. These Kihunter-X have a slightly different head structure from the ones seen on Zebes and the Bottle Ship; they now possess a beak-like mouth and their foreheads are colored purple instead of yellow. They can be found in Sector 2 and parts of the Main Deck of the Biologic Space Laboratories research station. Unlike the Bottle Ship's Kihunters, which were being converted into living weapons, those onboard the BSL were seemingly being observed for research purposes before X Parasites infested the station. Prior to their appearances, Samus encounters X infected/mimicked Zoros at first. These caterpillar-like creatures are eventually witnessed entering a pupa stage and later on hatching from their cocoons as Kihunters (still containing X Parasites): this sequence of events was the first to reveal that Zoros are actually infant/larval Kihunters.

Prime series
A similar-looking Space Pirate appears in concept art for what may be the Flying Pirate in Metroid Prime. This creature has shorter wings, longer legs, and a Metroid strapped to its back.

Weavel, a Space Pirate bounty hunter from Metroid Prime: Hunters, wears a Power Suit vaguely resembling a Kihunter.

Variations
Super Kihunters are featured in Other M. They are generally more durable, with crystallized structures and a darker skintone. These seem to be an advanced stage of the Kihunters' life cycle onboard the Bottle Ship.

The second variation is the previously mentioned King Kihunter, which is a large, mostly immobile creature connected to a central part of its hive. Its physiology is vastly different from a Kihunter's.

Super Metroid manual
SPACE PIRATES - KEYHUNTERS

"These creatures are pirates from another galactic system who helped rebuild Zebes. When they lose their wings, they spit powerful acid."

Super Metroid Nintendo Player's Guide
"Kihunters are fairly powerful and painfully persistent. Shoot them with Charge Beam shots."

Trivia

 * The room directly before facing the Spore Spawn is filled with Kihunters and small, unknown structures on the ceiling resembling eggs. Since both the flying creatures and the egg-like objects are found in the same room, it is possible that the latter are Kihunter eggs (containing future Zeros).
 * Kihunters are curiously located far from any Zero in Super Metroid, the game where both creatures made their first appearance.
 * While Kihunters are known to be Space Pirates in Super Metroid, Samus curiously makes no mention of this in Other M. In fact, Kihunters appear to have no affiliation with Space Pirates in that game and in Metroid Fusion. However, their feral nature in both games can be easily explained by the lack of a proper education and/or a supreme Pirate leader, just as how Zebesians in the Bottle Ship are steadily losing their intelligence without the presence of a controlling force like Mother Brain.
 * The ability to self-destruct is a trait that is only seen in the Kihunters living inside the Bottle Ship in Other M. It is possible that the scientists and researchers onboard the station added this ability to the species in order to turn them into efficient bioweapons.
 * The Kihunters are the only creatures who aren't damaged by an Overblast.
 * The Kihunters are the only creatures who do not receive a Charge Beam shot during Lethal Strike.
 * In Other M, a Kihunter can grab Samus if it has its wings. It then damages her by "pecking" her neck. If she dies like this, she will simply go limp in its arms, instead of the normal death cutscene.
 * In Other M Kihunters have a similar fighting style to the Aerotroopers from the Prime series: both will attempt suicide strikes when near death.
 * The Bottle Ship's Kihunters seem to be symbiotically related to Whipvines: five of the plants can be seen on the supports surrounding the Kihunter hive on the Biological Experiment Floor, and will attack Samus in a coordinated pattern along with the Kihunters. Whether this is a natural relationship or the result of MB's tampering is unknown.