Deutoros-pattern Scarab

"This thing is really starting to piss me off!"

- Staff Sergeant Marcus Banks.

Scarab The Type-47 Ultra Heavy Assault Platform (abbreviated Type-47 UHAP), more commonly known as the Scarab, is a Covenant ground based heavy assault vehicle.

Introduction
The Scarab is a towering Covenant walker, upheld on four long mechanical legs - it is different from the Covenant's other ground-based vehicles, such as the Wraith, Ghost or Spectre. Although it has been mistaken for the digging machines excavating CASTLE Base on Reach, it is in fact a combat vehicle. This is further proven by the fact that the Scarab employs its own defense turrets and a powerful, heavy main cannon mounted on its front and that the Scarab is heavily armored. This is unlike the digging machines excavating CASTLE Base during First Strike. It makes use of four large, mechanical legs for mobility, instead of a Boosted Gravity Propulsion System utilized by most other Covenant vehicles. This is an advantage that allows it to climb over obstacles that may have impeded other Covenant vehicles. It is the largest known Covenant ground-based vehicle, as well as the most resistant to damage. Its innards, though, are extremely vulnerable and easily destroyed, making it very prone to boarding actions, as demonstrated in the Battle of New Mombasa and the Second Battle of Earth. The Scarab holds squads of Grunts and Jackals, as well as a few Brutes to protect it from it being boarded, if anything manages to even get close enough. They have been used in many battles against the UNSC, such as on Reach before it was glassed and on Earth where the Spartans encountered a few in different locations on Earth.

Features
Scarabs are quite notable for their intimidating, animalistic appearance and enormous size. Each of a Scarab's legs is at least 90 feet tall. These legs are surprisingly deft and accurate for their size, and are even able to find holds in narrow places, such as a canyon on Installation 05 or the streets of Mombasa. These legs can also be used for weapons, as anything that gets in its way will be impaled by a monstrous pointed leg. Situated on top of these legs is a large, flat platform, with further pieces of machinery protruding up from this platform. Because of the Scarab's size and weight, they are not able to climb tall walls and buildings, and are not skilled at making sharp turns, as evident in Mombasa. As seen in Turf, particularly small and twisting city streets can overwhelm and crash Scarabs.

To defend itself from aerial attacks, the Scarab sports secondary turrets; two in Halo 2 that shoot large red plasma bolts similar to the Shade or Shielded Plasma Cannon, and one larger turret in Halo 3 that shoots large blue bolts, similar to an over sized Plasma Rifle.

The Scarab's most deadly weapon, however, is a large, forward-firing main cannon that projects a massive green beam of plasma. This beam can rip apart armored vehicles such as the Scorpion Tank or Pelican upon glancing impact, and is even able to destroy a heavily fortified, Forerunner-crafted Control Room door. The beam's drawbacks are its inability to move across an area quickly and the very long period of time that it requires to warm up and cool back down. It should also be noted that when the Scarab is firing its cannon, some type of liquid drips from the gun platform (possibly coolant or excess plasma). This cannon is also somewhat reminiscent of a larger version of the Gravity Cannon on the Prophets' thrones or the Assault Cannons wielded by Hunters.

In Halo 2, the Scarab seems to be captained by Ultra Elites, and is piloted by Major Domo Elites. While the Scarab in Mombasa had two pilots operating it, the one on The Great Journey, was operated by three Marines, Sgt.Maj. Johnson, Gy.Sgt. Stacker, and S.Sgt. Banks. Inside the Scarab there is also a small group of Ultra Grunts to guard the pilots. On the outer deck of the Scarab can be found any number of Minor or Major Elites, Minor or Major Grunts, and Minor, Major, or Sniper Jackals.

However, the Halo 3 Scarab does not appear to have any crew at all. The troops on board the Scarab appear to be just defending it, rather than commanding it. One theory suggests that the Scarab is controlled by Lekgolo worms. This is supported by the following evidence: It has been theorized that its function is as an excavator, though there is no accurate information to prove this. These theories are based on similarly shaped machines seen during the Battle of Reach. It has been speculated that it either uses its legs to excavate by digging or that it uses its main gun to carve its way through soil, rock or concrete, as the Covenant have used their plasma and energy weapons in a similar fashion before. The reason for using Lekgolo worms instead of the Elite pilots (as seen is Halo 2) could be interpreted as the Covenant's reaction to Sergeant Johnson capturing a Scarab during the final part of the game, thereby preventing such an event from ever reoccurring.
 * The core appears to be surrounded by pulsating cables that look similar to Lekgolo worms.
 * When you shoot the core, it bleeds orange blood, resembling that of a Lekgolo.
 * If you board a Scarab and kill all of its crew, it will keep moving.
 * On the level The Storm, when assigned to eliminate the Scarab the words "Kill the Scarab Tank" are used (rather that "Destroy the Scarab Tank"), possibly hinting that the Scarab is in fact living.

Battle of Reach
During the Battle of Reach, Spartan-104 describes seeing several large "insect like" excavating machines digging up CASTLE Base. If these were indeed Scarabs, which was not specified, they appear to be much weaker models, since Fred is able to destroy them using Plasma Mortars from a Wraith tank.

First Battle of Earth
When the Covenant first traveled to Earth, led by the Prophet of Regret, they had no idea that it could be populated by humans, never mind be their home world, leading to the Scarabs being used as highly effective siege weapons. One of the deployed Scarabs was encountered and destroyed by Spartan John-117 during the Battle of New Mombasa. A second Scarab was attacked by the UNSC Marine Corps in a section of Old Mombasa known as Turf, and was wrecked.

However, the deployment of Scarabs was not limited to the African theater of operations. Frederic-104 encountered a third Scarab during his mission in Havana, Cuba. William-043 destroyed it by crashing a fuel truck into it and igniting the combustibles.

Scarabs were also present in the Halo Graphic Novel in the story Second Sunrise Over New Mombasa though this could have been one of the two operating in New Mombasa.

Second Battle of Earth
During the battle to reach the Ark excavation site, the Master Chief and a Group of Marines were attacked by a Scarab. It took the combined efforts of Mongoose ATVs and Hornets to destroy it.

Battle of Onyx
Kurt also witnessed one arrive on Onyx during the Covenant Loyalist invasion. Elites were witnessed fighting for the Covenant on Onyx, suggesting that these events take place before the Uprising. This one operated as a first strike vehicle.

Battle of Installation 05
Another Scarab was stationed by the Covenant Loyalists on Installation 05 near the Control Room. Though guarded by a large group of Brutes, this Scarab was eventually retaken by the Arbiter. It was commandeered by Avery Johnson and used to break into the Control Room of Delta Halo, allowing the Arbiter and dozens of Councilors, Zealots, and Special Operations Elites to break into the Control Room and kill Tartarus.

Battle of the Ark
A Scarab attacked UNSC forces advancing on the Ark's Cartographer. With the help of Master Chief and three M808B Scorpion MBTs, the Scarab was brought down, and the offensive continued.

Two more Scarabs were deployed from orbit by Covenant Loyalists to hold off the UNSC/Covenant Separatist offensive on the Citadel, where the Prophet of Truth was located. Despite their superior defenses and numbers, the Scarabs and Loyalist forces were destroyed, thanks to the efforts of John-117 and UNSC "Hornet" pilots and ground troops.

Halo Wars
Scarabs will also appear in Halo wars as the Covenant's super ground weapon/unit, being capable of annihilating whole legions of UNSC forces with its main cannon, described in the E3 2007 demo as an "anti-everything gun". Their one weakness is the UNSC super weapon, the orbital MAC strike. During the developer walkthrough/demo, the characters in-game react as if they'd never seen a Scarab before, therefore possibly marking the Scarab's debut against the UNSC in the Halo timeline. Though this is not yet sure.

Variation
The Scarab has undergone a few transformations over it's canon life.

Halo 2
This is when the Scarab was first seen, rather than described, and appeared as a large, four legged, silver armored behemoth with an estimated height of 90 feet. It featured a deck on top which was guarded by numerous Elites, Jackals and Grunts along with a walkway going over the entrance to its control room. There were two spine mounted plasma cannons to provide anti-air defense. Its shell seemed to be invulnerable to damage from 90mm shells, missiles, .50 cal rounds and ANVIL HE missiles (the armor could be similar to the ship plating the Covenant use on their starships.) It proved vulnerable to boarding actions and destruction from inside.

Halo Graphic Novel
In here it has a very different appearance with a roughly crucifix shaped body, the across sections bearing dual cannons, neither end having a visible plasma cannon, its legs are a distinctly different shape (straight, with an 'L'-shaped joint to the body). It should be noted, however, that the story in which it appears, Second Sunrise Over New Mombasa, uses a very large amount of artistic license. The story is canonical, but the graphical side of the story is not artistically similar to the usual look of the games.

Halo 3
A likely conjecture is that this version of the Scarab is intended to be a weapon. Its color is changed to a shade of purple, like other Covenant war-ready vehicles, and it is better-defended, having superior weapons. It has been speculated that Scarabs of Halo 2 were not weapons, but rather mining tools that were deployed as emergency combat relief by Regret upon finding humans on Earth.
 * Its body has a different shape, being more bulbous at the end, similar to the Wraiths of Halo: Combat Evolved.
 * It seems to be wider, but not quite as tall.
 * It wields a smaller plasma beam that seems weaker (On Legendary the player is able to withstand sustained fire for a short amount of time (approx 0.8s), as opposed to the instant death of the Halo 2 Scarab gun).
 * The two anti-air turrets are gone, having been replaced by a single, large turret at the rear.
 * The flaps on the plasma beam are gone and replaced by two destructible stationary plates.
 * It now appears to have no crew controlling it, and it has been theorized to be controlled by Lekgolo worms.
 * It features a set of powerful belly-jets that allow it to survive a drop from low orbit with little or no ill effects.
 * The Main gun is also different, it is like a hose in Halo 3, instead of a straight beam appearance in Halo 2.

Differences aside, it still has many similarities to the old Scarab. There are three levels (or decks). The lowest is accessible when the Scarab has been temporarily disabled. This level features a Grunt-mounted Plasma Turret, and usually a Brute. There's a ramp that leads to the second level, where there are a varying number of enemies, depending on the level and difficulty. Usually, you can expect to find a few Brutes and Grunts. On this level, there are two more Plasma Turrets, aimed to either side of the Scarab. If you turn 180° immediately upon ascending the ramp to this level, you can go up the purple slope to the third tier. This is just an open, unprotected platform below the large turret. Past the turrets on the second level (round the corner) is the power core that must be destroyed to take down the Scarab.

Bungie has also stated in the September issue of EGM, that the Scarab uses an unscripted game AI (not to be confused with story A.I.s like Cortana) to create a more dynamic battle with it as it will roam across the battlefield of its own accord and attack targets in its path. This way it will no longer require a relatively easy boarding action every time but a tactical approach.

Halo Wars
It seems to be a combination of the Halo 2 and 3 Scarab designs, featuring an encased, Covenant purple chassis with a single spine mounted plasma cannon. The flaps on its plasma cannon, while bearing a similarity to those of the Halo 3 Scarab and also resembling a beak of a bird, operate like the flaps of the Halo 2 Scarab gun. They first conceal the weapon then it folds out into 8 separate pieces and shoots a sustained stream of plasma fire.

List of Destructible Parts
Note: If you destroy the Core, all parts of the Scarab will be destroyed at once, except for the crest of the Scarab Gun, and the armor protecting the core.
 * All four of the Scarab's legs are destructible to the point that the Scarab buckles. The armor on these legs can also be blown off.
 * The flaps covering the Scarab's main gun can be destroyed. Note: this does not disable the gun.
 * The crest on and around the turret can be completely blown off. Note: this does not disable the gun.
 * Two side door panels near the bottom rear can be torn off to allow entry.
 * The huge barrier protecting the Core can be ripped away from the back of the Scarab. Doing so will result in the Core being completely exposed, making it easier to blow up.
 * All Plasma Turrets.
 * The Core.

Primary

 * (1) Front-Mounted Cannon
 * Ammo: Super-Heated Plasma, presumably unguided.
 * Rate of Fire: 4 second stream; 30 to 40 per second
 * Movement of cannon: Through careful examination, one can see that the inside gun part seems to move forward from a cradle as the flaps open up.
 * Notes: The projectile emitted from the Scarab's main gun emits a neon-green/bluish glow, indicating extremely high temperature. As the gun fires, white, hot liquid pours from the barrel onto the ground. The gun's force is enough to destroy any vehicle smaller than the Scarab in a matter of a seconds, and could possibly melt through armor as tough as that of an interstellar war-ship.
 * Approx. Range: The effective range on a Scarabs main cannon is not exceptionally good, about .4 miles as seen during the Citadel and Cartographer battles, where its attack can easily be evaded if at a distance.

Secondary

 * Mounted Anti-Aircraft Turrets (Two in Halo 2, One in Halo 3)
 * Ammo: Super-Heated Plasma, (similar to Shielded Plasma Cannon)
 * Rate of Fire: 400-600 rounds/minute
 * Notes: Presumed computer controlled, but a close look indicates that it may be manually controlled. Can be shot off with little firepower. NOTE: In Halo 3 the AA cannon cannot be shot off and is invincible. The AA gun(s) are unsurprisingly extremely effective against aircraft.
 * Approx. Range: These weapons have a much better range than the primary cannon on the Scarab. They're extremely effective against airborne vehicles, but can also be used against ground-based vehicles, such as Warthogs or Scorpions. They are effective up to about 1.5 miles, which is a rough but evidence-based conclusion drawn from ships and vehicles with similar weaponry.

[[Image:Easy Shield.png|30px]]Easy
To defeat the Scarab's crew on easy difficulty, fire at its crew on the top of the Scarab when they appear with either a Rocket Launcher, Sniper Rifle or Battle Rifle. When you reach the end of the bridge it is recommended you collect a Shotgun, the second weapon is up to you but a Rocket Launcher is recommended. Throw a couple grenades at the surviving Grunts, Jackals and Elites to kill some of them and weaken the others' shields. Jump onto the Scarab and eliminate surviving Covenant with one of your weapons. When the top deck is clear proceed down to the interior. If you have a Rocket Launcher make sure it is loaded and fire two shots to kill the Ultra. You may eliminate the rest of the interior crew how you want.

[[Image:Normal.jpg|30px]]Normal
To defeat the Scarab's crew on normal difficulty fire at its crew on the top of the Scarab when they appear with either a Rocket Launcher, Sniper Rifle or Battle Rifle. When you reach the end of the bridge it is recommended you collect a Shotgun, the second weapon is up to you but our user usually has his second weapon be a Rocket Launcher. Throw four grenades at the surviving Grunts, Jackals, and Elites to kill some of them and weaken the others' shields. Jump onto the Scarab and eliminate surviving Covenant with one of your weapons. When the top deck is clear proceed down to the interior. If you have a Rocket Launcher make sure it is loaded and fire two or three shots to kill the Ultra. You may eliminate the rest of the interior crew how you want.

[[Image:Heroic.jpg|30px]]Heroic
To defeat the Scarab's crew on heroic difficulty fire at it's crew on the top of the Scarab when they appear with either a Rocket Launcher, Sniper Rifle or Battle Rifle. When you reach the end of the bridge it is recommended you collect a Shotgun, the second weapon is up to you but our user usually has his second weapon be a Rocket Launcher. Throw all your grenades at the surviving Grunts, Jackals and Elites to kill some of them and weaken the others' shields. Jump onto the Scarab and eliminate surviving Covenant with one of your weapons. When the top deck is clear proceed down to the interior. If you have a Rocket Launcher make sure it is loaded and fire three or four shots to kill the Ultra. You may eliminate the rest of the interior crew how you want.

[[Image:Legendary.jpg|40px]]Legendary
It's up to you how you want to end this: the quick way, or the slow but reassuring way. The quick way is to jump down onto the Scarab immediately, rush into the control room, blast all the Covenants in there to hell, and hope you don’t get run down from behind. The slow but reassuring way is to wait for the Scarab to get to the end of the waterway and fill up on rockets while waiting for it. At the end of the waterway, you can take out all the Covenant that come out, then jump down, go in, and finish off whatever Covenant are still inside. Either way, you win. Keep in mind, once you get inside, to get rid of the Ultra Elite first, toss grenades when needed, and be sure not blow yourself up with the launcher.

Halo 3 Strategies
Methods for destroying a Scarab:

Internal Destruction
A few of the methods below require you to board the Scarab and destroy it from the inside. Here's how:
 * There is a walkway on both sides of the Scarab so if your lucky you can jump on them when it is down.
 * DON'T go right around to the back. On each side of the Scarab, there is a purple panel that can be blown open. They are located towards the rear of the Scarab, just around from the main entrance.
 * Destroy one of these side doors, jump in and kill whatever is waiting for you. The reason you go in the side is the Plasma Turret located at the main entrance. This way, it doesn't fire at you as you approach.
 * Go up the ramp. Turn 180°, and kill the enemies down one or both sides of the Scarab in whatever way you see fit.
 * At the very back of the Scarab (above the main entrance), there is the Core. It looks like a bright blue disk.
 * This disk is an energy shield. Shoot at it until it disappears. Next there is a protective metal cover, shoot this off as well. Under this cover is a sort of X shape with a blue light in the middle. Shoot or hit this until the light turns red.
 * If the Scarab is disabled, you can jump up onto the ramp located next to the Scarabs main weapon. From there you go straight and turn near the rear of the Scarab and you will see the core.
 * Turn and jump off the back of the Scarab, and get as far away as possible, because if you're too close, the explosion can kill you.
 * Watch the pretty blue explosion caused by your handiwork (optional).

Airborne
There are a few ways a Scarab can be engaged from the air. The only thing to remember, really, is that the AA gun on the back is just that; an Anti-Aircraft gun. Give it a chance and that thing will tear a Hornet or Banshee apart in seconds. So stay close to the back and you will find a little sort of blue bolt like that of a Wraith (in Halo 2). Shoot it and the back piece falls off, leaving the core exposed. Shoot it, get some distance between you and the Scarab, and watch the fireworks.

Aerial Drop
This is especially effective when fighting more than one Scarab in Co-op. Have one player fly a Hornet, whilst the other player rides in one of the side-seats. The first (piloting) player lands on top of the Scarab. The second (non-piloting) player, gets off the Hornet, and proceeds to destroy the Scarab internally. The first player, meanwhile, flies to the other Scarab and either gets off on top of the Scarab and follows the second player's example, or engages the Scarab in any way they see fit. This can be done in a Banshee, but obviously only by one player.

In single player, if the player rides in the side seat with a marine in the pilot's seat, the marine will let the player board the Scarab. When the Core has been destroyed, the marine will return to pick up the player; usually remaining stationary above, or even touching, the Scarab's top-most deck. (Note: Sometimes the Marine may not come back, so be ready at all times to jump off the Scarab without your plane.)

Aerial Drop for Legendary (co-op)
This tactic is really only useful in legendary mode when fighting more than one Scarab. Have one player fly the Hornet, whilst the other player is riding in one of the side seats. The first (piloting) player hovers over the top of the Scarab for around 2 seconds whilst the other player jumps out and aims to land on the Scarab. Soon as the second player has left the Hornet the first player should either be flying into the mountains to the left or to the right under cover from the Scarab. This means that if the second player should die, he will get re-spawned next to the Hornet ready to take off and repeat the drop off run again.

Direct Assault
Keep circle-strafing around the Scarab, and shoot at the large blue disc located below the AA gun on the rear of the Scarab. This disc will turn red, then disappear. Keep shooting at where it was, until a large chunk of armor falls off the back of the Scarab. This barrier protects the Core. Once the barrier comes away, it may be advantageous to shoot at the legs until the Scarab goes down so that you can get an easier shot at the Core. Alternatively, keep circle-strafing and try and hit the Core, it doesn't take much to destroy.

Indirect Assault
Use your aircraft's weapons to take down a leg, using your superior three-dimensional maneuverability to avoid destruction. Land on the ground, get out of your aircraft and proceed to take the Scarab out from the inside. This method is a bit redundant, unless you're playing meta-campaign, and want the points from all the individual kills inside, which you otherwise wouldn't get.

Bridge Jump
Go to an elevator, go across the bridge, and wait for the Scarab to get right in front of you. Then, jump down and you'll land on top of it. Beware the front cannons. Of course, this can only be done on the level The Storm.

Land
Land combat depends hugely on what vehicle you use.

Scorpion
You have two choices. You can either engage from an extremely long range, or an extremely short range. The Scorpion is too slow to challenge the main gun from a middle distance.

If you are playing Co-op, it's usually best to keep the Scorpion at long range, whilst the other player uses a fast, maneuverable vehicle, such as a Ghost or Mongoose to draw Scarab away. When your partner has forced the Scarab to present its back to you, fire at the barrier protecting the Core. Once that has been destroyed, fire at the Core.

If you are playing single player, run the gauntlet, and charge straight at the Scarab. You may take a bit of fire, but you will soon move below the Scarab's minimum depth angle. Place yourself directly below the Scarab, and fire at the leg joints. Once the Scarab goes down, MOVE! If the tank is below the Scarab when it drops, it will be crushed and destroyed. Either get out and finish the job from the inside, or move to a place where you can see past the barrier, and fire on the Core.

Alternatively, fire at the armored "flap" covering the joint halfway down the Scarab's leg. On Legendary, as few as four direct hits can make the Scarab go down. You can then drive in close and destroy it in any way your heart desires.

Or, in the tank you can circle the Scarab and shoot the core with the main gun without boarding or blowing the back of you might want to disable the legs first but you can drive under and rotate the turret to find a good angle. This is a useful method for quick destruction of scarabs on legendary

Mongoose
There are a few ways the Mongoose can be used. The easiest way is to put a Marine on the back with a Rocket Launcher (don't use your Co-op partner, as they run out of ammo), and drive around under the Scarab until it goes down. Then dismount the Mongoose, and hop in the back of the Scarab. Proceed to destroy it from the inside, or fire directly on the Core, since the angle will be easy enough to get. Only do this if you have your own Rocket Launcher or Fuel Rod Cannon, since the Scarab will more than likely have recovered before you can do enough damage with any other weapon.

Alternatively, the large earthen hills on the level The Covenant make excellent ramps for jumping a Mongoose directly onto the Scarab. Drive your vehicle as far to the rear of the ramp as possible, touching the canyon wall, and wait for the Scarab to turn to face you (be aware that the other scarab can still attack you, so be ready to move if necessary). Once your target scarab is in position, drive as quickly as possible and try to land on the main deck. Fight the enemies, or just run directly to the Core. It is rarely worthwhile to try to recover your vehicle, and it can sometimes survive the Scarab's explosion anyway.

Warthog
The Gauss Warthog is reasonably effective at bringing a Scarab to its knees. Similar tactics apply as with the Mongoose, except you have more firepower. This is a nice vehicle to use on Co-op, as your partner can gun or drive, and you can still have a rocket-armed Marine passenger. Also, while in the level The Storm, if you get a Troop Transport Warthog you can fill it with Marines equipped with rocket launchers. It can be more effective than a mongoose with someone using a rocket launcher, but because it is slower, be careful not to get destroyed by the scarab's legs.

The M41 variant of the Warthog is not as effective, but can still get the job done. Also, see above for an alternative strategy, but replace "Mongoose" with "Warthog".

Wraith
Don't attempt this unless you are VERY proficient with the Plasma Mortar. The Wraith's turning speed is too slow to make a short-range attack feasible, so it has to be engaged from long range. However you can use a wraith at close range against a scarab as long as you stay underneath it and fire as fast as you can at one of the legs, then follow up by boarding it or firing at the core. This is considerably more difficult than using a mongoose with a rocket launcher armed marine riding on the back, or even just going on foot  with a rocket launcher, so a long range strategy is much more advisable. Either aim for the legs, and try and get close enough to finish the job yourself, or, in Co-op, have your partner draw the Scarab's attention from you, and fire directly at the barrier, and subsequently the Core. Remember to lead your target, as the mortars travel quite slowly.

Another way to utilize the wraith is to hjack one form a pesky brute and give it to a marine which they are proficient with bombing the scarab form long range with its plasma motor

AA Wraith
If you are skilled enough to use the AA Wraith "hack" ( see How to Pilot an AA Wraith ) to successfully use the vehicle in combat, it can prove quite potent against a Scarab. This tactic can only be used in the level "The Storm". Once you have reached the part in the level where you are on a Mongoose with a Marine with a rocket launcher on the back, you will find two AA Wraiths. Destroy one of the them and dismount your Mongoose. ( Note: make sure that the Ghosts and Choppers have also been destroyed. Otherwise they will make it very hard to get to the AA Wraith. ) Use the "hack" and ta-da you have a nice anti-Scarab weapon. Mop up the rest of the Covenant and wait for the Scarab. Remember that if you get out of the AA Wraith, it will explode. Take cover near the platforms with the rocket pods on them so you have a place to hide from the Scarabs withering beam. You can "button-mash" with the AA Wraith and let loose hell against the Scarab with the six Fuel Rod Cannon. Just fire on its legs till it goes down and then go around to the back and either board it or blow up the core cover and the core with the AA Wraith. Also remember that the same basic rules as using a normal Wraith against a Scarab apply here as well.

Ghost
With the Ghost, you may shoot accurately, and slowly destroy the armor on one of the Scarab's legs, therefore kneeling it and making it possible to board. You can try this at least on The Ark and on The Storm levels. Remember to be wary about the Scarab impaling you with one of it's pointy legs, and with no one to distract the Scarab, it can be very dangerous even to approach it on higher difficulties. This strategy is only for fun, as it is considerably slower and more dangerous than any other.

On Foot
Get as many explosives as you can. Rockets, Fuel Rod Cannons, Grenades (Plasma, Spike and Incendiary), Missile Pods and Brute Shots are the ONLY viable weapons. Use cover to get as close to the Scarab as possible. Ideally, you want to be underneath it. Pick a leg, and fire on the joint. Use everything you've got. Don't change to a different leg, and don't fire anywhere other than the joint. If you manage to get the Scarab down, proceed to destroy it from the inside. You can also use a power drain to destroy a scarab. Take down the shielding and then fire two BR bursts into the middle of the core and then throw down a power drain. This for some reason will not get you the 'We're in for some chop' achievement.

On "The Storm" you can also board the Scarab by riding the two crane's lifts and jumping onto the scarab as it passes by, but be warned if you miss you might fall to your death. It is also possible to land a Mongoose or a Warthog in this manner but is very difficult due to the scarab moving as you land, or your rocket marine(s) blowing you off course. This marine also, if you manage to land on the scarab, will fire his rockets, killing himself and you if you are nearby. It is suggested to give your marine another weapon or make him get off the mongoose entirely.

There is also a sniper rifle on the crane closest to the door that you leave the lake bed through (the right-hand crane when looking from the cliff inwards). This is useful for picking off enemies on the Scarab before you jump on.

Dumpster
This is only possible through the use of the so-called "Flying Dumpster" on The Storm. If both co-op players get inside the dumpster while it is on its side, you may make it fly by repeatedly pressing the Jump Button. Note: It is nigh impossible to control the dumpster and, therefore, nigh impossible to attack the Scarab. If you do land on the Scarab, proceed to slaughter its defenders and destroy the core. If you need help on flying a dumpster, there are many tutorials and other useful videos on Youtube.

General tips

 * On each leg, just below the joint, there is a small blue square. This is what you want to aim for, the weakest point of the leg, and firing at it will cause the Scarab to go down much faster.
 * The core is extremely vulnerable. If you see a shot from the ground, and are confident you can make it, go for it.
 * Plasma grenades don't stick to Scarabs, on the legs or elsewhere. They can be used to take out a leg, but only by making it balance atop the joint.

Character Compatibility

 * Grunts
 * Jackals
 * Elites
 * Marines (only Johnson is observed doing so)
 * Brutes (only in Halo 3)
 * Hunters (pilot Scarabs in Halo 3)

Trivia

 * There is a scarab (h2) on the halo custom edition maps Hotzone, Unreal and Extinction
 * Through close, repetitive analysis of Hunters and Scarabs (and the repeated death from each that came with it) made by Destrond, the worms on the Scarab are Lekgolo. Being able to get in close, the worms on the Hunters move in the same pattern as on the Scarab, and bleed the same bright orange blood. Also, there have been repetitive announcements that Bungie has made saying that this is only the start of the types of Lekgolo that can be found, stating that this is most likely one of them.
 * A scarab is an Egyptian beetle that was worshiped as a manifestation of Khepri, an Egyptian god who drove the sun across the sky.
 * There is a glitch in Halo 3 where if you jump on a leg of a Scarab, and the leg moves up and you jump at he same time it will fling you quite far.
 * The Scarab Gun is a weapon that players can pick up in Halo 2; it looks like a plasma rifle and can be found on the level Metropolis as seen in a video. It fires the same projectile as the Scarab's main gun, and it never overheats and can fire continuous rapid fire.
 * In Halo 2, it is possible to look inside of a Scarab. On the level Metropolis, when the Scarab stops at the end of a level, hop on the Scarab and kill all but ONE enemy. Then, go to the main gun and hop down in the gun. Keep on one of the latches and walk towards the Scarab. you will be able to look inside the Scarab. You will also be able to detach your torso from your legs and see them walk forwards. You can try and jump on one of the Scarabs legs and get back on the Scarab, but due to it moving back and forth, it might be difficult.
 * It is possible that Scarabs are the Sharquoi mentioned in Conversations from the Universe.
 * In Halo 3, when you shoot the Scarab's core after you take out all of the shielding, you can see what appears to be Hunter's blood coming out of it, you can even see the worms come out. There is also an audible 'squishy' sound when you stand next to the 'worms' in the conduits. Another hint that Halo 3 Scarabs are controlled by Lekgolo worms is that, on the level The Covenant, after the the two Scarabs land they stand up and seemingly shake themselves. It would serve no purpose for them to do this if controlled by a pilot, but might make sense if they are controlled by the worms and were shaking off the impact. However, because the Halo 2 Scarab had to be controlled to move and the Halo 3 one didn't, the Halo 2 ones are normal machines, and the Lekgolo worms might only control the Halo 3 Scarabs.
 * It is also notable that when a Scarab's leg is disabled, it emits a loud beep, much like that of a reversing truck (except of a lower pitch). This effect is perhaps a nod to the same death sequence (and sound) of the Juggernaut flying tanks in a previous Bungie game Marathon.
 * The Scarab, once the core has been compromised, takes 7 seconds to explode (Going with the usual 7 "nods" Bungie puts into the games).
 * The Halo 3 Scarab was recreated in Halo Actionclix and as of the game's release is the largest figure ever made by Wizkids, the game's creator. A battle-damaged version was released at the 2007 San Diego Comic Con for $250, which included the Scarab, two outdoor maps, an indoor map (representing the scarab's interior), four character cards, and rules for both the Scarab and the game itself. A normal one was also released at select retailers in November 2007.
 * Azathoth117 asks: "Are the orange worm-type thingies in the back of the Scarab the same things as the worms in Hunters, or is it just superficial resemblance?" Bungie:"The resemblance is not just superficial. A future DLC map might expand upon that mystery."
 * The Scarab is the only manufactured Covenant vehicle that is not named after some sort of spirit, although in Egyptian legend the bite of a scarab beetle resulted in death.
 * In a Halo 3 Video Documentary (ViDoc) about the new Scarab, the art directors stated that the Scarab in Halo 2 had a horrible design; "It looked like a basket that you could pick up and walk home with."
 * Scarabs are rumored to be featured vehicles in the Legendary Map Pack which may be drivable, this is so far proven false. Unless it's a surprise forge vehicle, it won't be there.
 * On both sides of the Halo 3 Scarabs, there are blast doors that can be blown off, but it's still unknown if the entrances can be accessed. The best way to find out would be using a Hornet in co-op and have the additional player/character ride on either sides of the hornet then attempt to jump into the entrance once within a close enough range.
 * If you find you may not be able to get away from a Scarab in time before it explodes, you can throw a Bubble Shield down. The shield will protect from the explosion regardless of how close you are to the Scarab.  It should be noted that doing so on the Scarab will not work, and that any pieces of armor or the one of the legs from the Scarab can still pass through the shield and potentially kill you.
 * In Halo 3, on the level, "The Covenant", two Scarabs are deployed by the Covenant Loyalist's fleet overhead, to defend the Citadel. However, on the previous level, "The Ark", Rtas 'Vadum claimed that "Truth's fleet lies in ruins".
 * A Scarab's explosion is extremely visible, as Rtas 'Vadum remarks how he saw the explosion of a Scarab "from orbit."
 * In the Halo 3 level The Covenant, it is possible to make the Scarab glitch underground. To do this, you must kill either of the Scarabs very quickly. If it has not yet completed it's landing animation when the killing blow hits it, the glitch will happen. This can be done with a Hornet: either drop on the deck and destroy the core ASAP, or use the Hornet to blow its back off and shoot the core. The first method will send you flying out of map, usually killing you.