As you progress through the Ridley Region, you will encounter a flying creature known as Imago.

Defeat Imago

Shoot the backside of Imago, i.e. the part with the stinger. Don't let Imago chase you. Instead, follow behind it and shoot it as you go. When you reach the left or right side of the room, crouch down into Morph Ball and don't be up against the wall. That way, you'll be far enough down that Imago won't hit you when it moves downward from above.

Eventually, Imago will start shooting stingers at you, but you can avoid this if you position yourself correctly: if you're near the right side of the room, stay next to the base of the slope that leads up to the door on the right; if you're on the left side of the room, stay just to the right of the pile of eggs.

After you hit Imago enough times, the back part of its body will fall off. Go to the right side of the room, then go back to the left side, and Imago will fly from the right side and crash through the pile of eggs.

Go to the left where the eggs were and pick up the Super Missile Tank. Super Missiles deal more damage than regular missiles, and you can shoot them at green doors to open them. You can switch between Super Missiles and regular missiles by pressing Select.