From Halopedia, the Halo wiki
Scarabs are quadrupedal mining platforms that are part of a larger class of constructs known as Excavators. Out of nine tiers of Excavators they are classed tier-four on its scale. Scarabs are all fitted with a focus cannon for destroying targets or mining operations. Scarabs are driven by hundreds of Rhulolekgolo, which function as a gestalt intelligence. For this reason, the Scarab was not formally considered a vehicle by the Covenant, but was employed as an ultra-heavy infantry unit directed by a single colony of Lekgolo. Nevertheless, Scarabs are generally deemed too valuable to operate without support, and are almost always accompanied by a robust escort.
- Type-29 Scarab - The largest model with the most powerful focus cannon, known as the Super Scarab.
Two models of the Type-47, the default and most common, Scarab exist: the Deutoros and the Protos. Both models are extremely powerful, possessing potent armament and armor.
- Protos-pattern Scarab - A model of the Scarab specialized for artifact-retrieval. It was fitted with a focus cannon and two separate suspensor-mounted heavy plasma repeaters. 
- Deutoros-pattern Scarab - The most common Type-47 Scarab. It was fitted with a focus cannon and secondary heavy plasma cannon.
- Barukaza Workshop Scarab - A model heavily modified by the Armory of Barukaza for the Banished and armed with an unstable plasma beam that deals incredible ground-target damage complimented with Thrasher missiles for air defense.
- Volitile Scarab - This variant of the Banished Scarab was created after Voridus learnt how to harness the power of the Installation 00's Infusion gel.
Unidentified Scarab encounters
Fall of Reach
During the Fall of Reach after discovering the Forerunner ruins under Menachite Mountain on Reach, the Covenant attempted to use several Scarabs to dig deep into the mountain's caverns. However, the walkers were destroyed by Zurdo-pattern Wraiths manned by Spartan-IIs.
Battle of Havana and the Onyx Conflict
During the Battle of Havana on Earth, Spartan-II Blue Team destroyed a Scarab. Another Scarab that had an onboard reactor was deployed during the Onyx Conflict by the Joyous Exultation Covenant.
Like all known Excavators, the Scarab is named after an insect rather than a supernatural entity like most Covenant vehicles. However, scarabs do have significant supernatural relevance in Egyptian mythology.
Early concept art for Halo Infinite depicting what appears to be a variant of Scarab firing on a spacecraft.
List of appearances
- Halo Waypoint: Universe, Vehicles, Scarab
- Halo Encyclopedia (2022 edition), page 279
- Halo Wars 2, Phoenix Logs, Banished Units Scarab
- Halo Wars 2, Phoenix Logs, Banished Units Volatile Scarab
- Halo: First Strike, Chapter 12
- Halo: Ghosts of Onyx, Chapter 23
- Halo: Ghosts of Onyx, Chapter 33
- Halo: Envoy, Chapter 5