It states on wikipedia that their budget with the flood was insufficient so they classified the grunt and other species as "non-combat units" the hunter, though is not infected but... Made? I guess? The drone is infected and evolves to a drone that projects sharp... "needle like" projectiles, after this evolution it turns into a hunter like flood. This of course leads to the question of, do regular drones turn into hunters somehow? as in, are the drones and the hunters, or the yanme'e and Mgalekgolo related?