Imago was a boss encountered in Metroid: Zero Mission. It was a giant bee-like creature encountered in Ridley's Lair that attacked Samus Aran for destroying its eggs. In the Japanese website of Zero Mission, the Imago and its previous forms are given the title Giant Evolving Bug.
Imago's larval form, the Kiru Giru, were found in Norfair; Samus encountered four of them during the course of her Zero Mission. The first two she encountered were free-roaming and could be killed by damaging their softer underbellies. This could be accomplished either by shooting from underneath the larva using the Wave Beam or by placing Bombs in the larva's path. While traveling through a Norfair tunnel infested with parasitic Tangle Vines, Samus came across a third larva that appeared to have been almost fully consumed by the vines.
Soon afterwards, Samus encountered a fourth larva that had been suspended in midair by the Tangle Vines ensnaring it. She freed the larva by using a nearby Winged Ripper to reach a position where she could fire Missiles at the vines holding the larva up. Once freed, the larva plunged into a stone platform, opening a passage leading to Ridley's Lair. If the Ripper is directly underneath the larva when it falls, it is killed instantly.
Soon after arriving in Ridley's Lair, Samus saw the larva forming a cocoon after having dug deeper underground. Samus returned to Norfair and followed the larva's tunnel only to find that it had already molted. Following its burrow further, Samus discovered a new chamber lined with eggs; as she approached a blocked-off Super Missile Tank, she accidentally broke several of the eggs. Enraged at the threat to its offspring, the fully-grown adult Imago promptly attacked Samus.
Imago attacks by flying around and attempting to impale Samus with its deadly stinger. It will also fire needles from the stinger, and they can be destroyed for power-ups if necessary. This can be easily avoided, though, as Imago flies at a height that allows Samus to simply duck or use the Morph Ball to pass under it. Once she deals enough damage to its large glowing abdomen, the Imago's stinger is destroyed, leaving it only able to to ram its opponent. At this point, if Samus approaches the wall that blocks off the Super Missile Tank, the mortally wounded Imago will crash through the wall and expire, giving Samus access to the power-up.
Yoshio Sakamoto: "They're the same life form. But I don't know if it has tenacity. Samus only coincidentally narrowly saved the Kiru Giru captured by the Karamutsuta (Tangle Vines) from certain death, and afterward, the reason Kiru Giru that became an Imago attacked Samus was because Samus had trampled on the eggs it had created."
- According to the Metroid Manga, the adult Imago isn't a part of Zebes' natural ecosystem but a mutant beast created by Mother Brain.
- The battle with the second free-roaming Kiru Giru is very similar to the battle with Crocomire in Super Metroid.
- The music tracks heard in the rooms of the first two and fourth Kiru Giru sound very similar to the theme of Spore Spawn and Botwoon of Super Metroid and subsequently, Nettori from Metroid Fusion. In addition, the ensnared larva releases small spores much like the mentioned bosses. The larva's spores more closely resemble Botwoon's, as they glowed and flew in a straight path, contrary to Spore Spawn's which floated down the room in a swaying motion.
- If Samus attempts to kill the Imago using a Spin Jump Attack, a glitch will stop it from moving. This forces the player to reset the game. 
- Imago is the scientific word for the adult stage of an insect, such as a butterfly.
- There is an H.P Lovecraft creature called a Mi-go, which coincidentally looks very similiar to the Imago. It may have been the basis for the look of the Imago.
- If Samus has acquired a Super Missile Tank through Sequence Breaking, she can open the Green Hatch and skip the Imago entirely.
- There is a method to avoid damage entirely when facing Imago. By positioning Samus barely at the bottom of the first slope upon entering the chamber (her feet should be even with the first 'indent' near the bottom of the slope) and crouching, Imago's stingers will hit just in front of her and sail over her head while Imago remains unable to ram Samus. Samus will remain able to shoot Imago's abdomen at least twice per pass.