Found throughout most of western Uldum, in all Assaults phases. Note: the red variant of this scarab is extremely rare - perhaps 1-in-100 or more spawns. You may need to search for a while, even kill off the blue scarabs, in order to get one.
Spawns during the 'Ambushed Settlers' quest events, which only occur during Aqir Unearthed Assaults.
Level scaling: Most NPCs will scale with the Hunter's level, within the constraints of their level range. Hunters can tame regular NPCs up to 2 levels higher than them, but can only tame elite NPCs of the hunter's level or below.