Skree

Skrees are native inhabitants of Zebes and are a type of enemy which have appeared in several games since the original Metroid. Roosting from ceilings, these bat-like creatures will quietly rotate their wings; which are also used as pincers and shovels; around their comparatively small thorax as they wait prey. Prey is known to be as large as an abnormally tall human (i.e. Samus Aran), though actual range is unknown; it is even possible that this large prey is not even used for sustenance, but rather is considered an intruder. Once prey is located, the Skree will proceed to dive-bomb said intruder as they enter an approximate 10 foot radius (Several Samus' can lay down on the ground in this radius), resulting in either self-destruction into harmful shrapnel (in Metroid or its remake, Zero Mission) or their escaping by drilling their way underground through the use of their rotating wings (in Super Metroid or Other M); this digging will release damaging shrapnel from the ground identical to the shrapnel released from their exploding bodies. When Samus kills Skrees In Super, they will also explode into shrapnel, unlike any other Metroid game in which the species never launch any projectiles when killed; possibly representing an adaptation that spread through the population post-Zero Mission along with the disappearing of the self-destruction on contact with the ground.

There are two known varieties: a green variety which appears in the first part of Brinstar, and a blue variety that appeared later in Brinstar after Samus receives the Varia Suit in Metroid. Said blue variety is colored as gray in Metroid: Zero Mission, but the color is the only known Blue/Grey Skree inconsistency between the two games. The blue ones are harder to kill; possibly possessing a thicker exoskeleton; and have a larger blast radius upon self-destruction.

Skrees in Metroid: Other M no longer burrow themselves into the ground (possibly due to the Bottle Ship's metal tiles on the floor preventing them from doing so or genetic alterations) in an attempt to damage Samus; rather, after missing their target, they will stand on their feet and swoop back to the ceiling. They will keep repeating this process either until she kills them or until they unpredictably self-destruct, harming Samus if she is near the blast radius.

Skrees also appear in the Metroid Manga, where a pair of them unintentionally save Samus and her group from a pair of Space Pirates by instantly killing them via dive-bomb.

In the Metroid Prime games, the creatures known as Shriekbats (and their many strains) play the same role as the Skrees (ceiling hanging dive-bombing enemies). According to the manga, the species do not seem to be related, as Samus explains to Kreatz and Mauk that Skrees are one of many predators found "nowhere else in the galaxy."

Metaree
Metarees are a strain of Skrees encountered only in Super Metroid. This strain has a light brown color and has what appear to be mechanical drills for wings, though it is unknown if this is acquired naturally or artificially, the latter possibly through enhancements made by Space Pirates.

Cyclaw
Cyclaws are another variation of Skree. Black in color but still possessing the same basic structure, they appear only in the Bottle Ship from Other M. They attack like an average skree but have an added attack which consists of latching onto Samus and self-destructing. These differences may be attributed to genetic engineering by the Galactic Federation.

Metroid manual
"They stick to the ceiling and lie in wait for Samus. When he approaches, they spin downwards to attack him."

"They use their wings like drills to descend from the ceiling and attack Samus. Be careful of rock splinters when they are digging into the ground."

1986 manga
"When Samus draws near, they will spin and attack. When they burrow into the ground, be careful of the rock fragments."

Official Nintendo Player's Guide
"It attacks from the ceiling screwing down like a drill. If it pierces the ground, it blows itself up."

Super Metroid manual
"These creatures hang down from ceilings and drop as intruders approach."

Super Metroid Nintendo Player's Guide
"They will dive-bomb you as you pass underneath. Dash!"

Zero Mission manual
"These creatures hang from the ceiling and drop down to attack when Samus passes underneath. They then self-destruct, inflicting damage with shrapnel from their exoskeletons."

Official website
SPECIMEN ID# G2-003 "Specimen prefers to hang upside-down from ceilings, diving after prey with razor-sharp wings. Interior analysis shows symmetrical pockets of combustible gases, causing creature to explode on impact. DANGER LEVEL: MODERATE."
 * Curved feet and claws
 * Jagged wings
 * Combustible gas pockets (Head)

Metroid Fusion
Interestingly, despite being one of the Metroid series' signature enemies, the Skree is absent in Metroid Fusion. However, beta trailers show that an X Parasite mimic of the Skree was to appear in Sector 1, but was dropped for unknown reasons. Screenshots show that the sprites were reused from Super Metroid. These remain in the game's data.

Metroid Prime
Even though Skrees are replaced by the Shriekbats in this game, there is concept art in Metroid Prime and Metroid Fusion: Prima's Official Strategy Guide that feature what appear to be two variants of a creature identical to the Skrees seen in games outside the Prime series. While one of them has an orange and yellow color, the other possesses the Skree's green color scheme. Their eyes also resemble a Skree's, and are largely different than a Shriekbat's. Both artworks appeared in the Brady Metroid Prime Official Strategy Guide on page 119 along with Ripper artwork.

ShineSparkers: ''During the development of any game there are ideas that don't make it for various reasons. Can you tell us about any concepts or models you came up with for Metroid Prime that didn’t make the final cut and why?''

Mike Sneath: ''The entire first years worth of characters I modelled for the game were cut. At first we were making all the enemies looking just like the old Metroid 2D enemies. Nintendo, later decided that they wanted the enemies to have a new look so we scrapped all of those creatures. These weren’t just models that were scrapped but these were enemies that had a full set of animations and some even had AI programmed. I’m actually very glad Nintendo made that call because I think the newer designs that Jones and Keller came up with was a big improvement over the original 2D designs.''

Trivia

 * One Skree appears in a microgame based on Metroid: Zero Mission, in WarioWare D.I.Y.
 * Weavel is a Space Pirate that was reconstructed following an incident in Brinstar during Samus's first mission on Zebes. Seeing as the only Pirates present in said area at that time were the pair attacked by Skrees in the manga, Weavel might possibly be one of those two.