Duvalia have a health value of 6000hp. They appear only on Base Majini or Wetlands Majini who are infected with Type 3 Plagas, however in "The Mercenaries Reunion" and the "Desperate Escape" chapter, Town Majini will turn into Duvalia as well.
Will send the player into the Dying stage. If a Duvalia bites the player a second time before he/she is rescued by the partner, it will remove the entire upper body, causing instant death. The animation is fast and quite similar to the Headbutt.
A Duvalia's legs can be fired upon repeatedly to make it kneel and open up its upper body, allowing a clear shot at its core. Even if the Duvalia has leg armor, the ankles and feet are still vulnerable. Shotguns are especially useful for that.
In general, keeping your distance from a Duvalia renders it harmless. Even if it is fought in a confined space, you can use the windup of its attacks to get away and shoot its weak points. A good way to remove the Duvalia as a threat is to climb any area with a ladder, as lacking arms, it will not be able to follow. This does not work in Mercenaries, however, as the Duvalia will simply jump there.
If a Majini is swelling with bubbles, it means it's going to turn into a Duvalia. However, this should not be confused with certain Base Majini who swell up and explode - the animation may be similar, but the result is radically different.
A easy way to know if the Majini is going to explode is to shoot him again. His body will instantly explode if the player hits him one more time with any weapon.
Also, differently from the Duvalia emergence animation, when about to explode he'll inflate like a balloon (with smoke coming out of the back) and grab his head. The animation for a Base Majini exploding is also longer than the emerging Duvalia animation.
Chapter 3-1: Spawns after retrieving the Shaman slate along with a large wave of Majini.
Chapter 6-1: Spawns in a completely bulletproof Base Majini after the partner is trapped in one of the containers. This one is required to defeat, since it holds the Crane Keycard. Another one spawns in a Majini at the end of the underground route of the cargo hold, but is not required to defeat.
Chapter 6-2: Spawns in another completely bulletproof (Except for the head) Majini in the end of the hallway leading to the bridge. This one is required to defeat, since it holds the Bridge Keycard.
Duvalia returns in Resident Evil: The Mercenaries 3D as mini bosses in certain missions throughout the game. They function exactly as they did in Resident Evil 5 and can still be killed by flash grenades.