Warrior Xenomorph

From Alien Species

The warrior caste alien, or more commonly known as simply the warrior, is believed to be an advanced form of the Drone caste alien. In most cases the Warrior looks the same as a Drone except that the dome on top of the head is completely gone. The most widely accepted theory regarding the ridges is that the Warriors have matured after a few weeks while Drones are newly born. According to some games, such as AVP Extinction, the Warrior is an entirely separate caste than the Drone.