Capable of absorbing vast amounts of damage compared to most bugs, Shieldbugs have massive, armoured limbs that give them their name. On Normal difficulty with Onslaught mode disabled, they are first encountered in Deima Surface Bridge.
- Shieldbugs are a significant threat to your marines, who will have quotes about them if they encounter them.
- The best way to kill a Shieldbug is to attack it from behind, aiming for the yellow-white cluster on the rear of their body. Attacking from the front is ineffective, and the Shieldbug has a strong melee attack that can knock a marine a good distance - so be careful.
- Shieldbugs tend to pick a single marine (typically the one closest to them or the one attacking them) and then advance towards them slowly. The other marines then have (and should make the most of) the opportunity to flank and kill the Shieldbug while it's distracted.
- When you're alone and lack any grenades or weapons that can stun, the only viable strategy to pursue is to draw the shieldbug into his defensive mode and wait for him to strike you. This will momentarily stop him from rotating towards you and allows you to attack his back.
- Avoid confronting Shieldbugs near a bridge or cliff. If the Shieldbug manages to connect at the right angle, it will knock you off the edge into oblivion, killing you and preventing fellow marines from scavenging your gear.
- Avoid fighting Shieldbugs on a wall as they can knock you down in front of them and continually slam you for heavy damage until you succumb or somehow move out of the way.
- The Grenade Launcher's grenades can be arced over a Shieldbug's armoured limbs to strike it from behind.
- The Tesla Cannon or Tesla Sentry Coil "stun-locks" Shieldbugs and makes them essentially freeze in place. This can be important during the Shieldbug Rush during the Sewer Junction mission.
- Any electrical attacks, including the Prototype Rifle's stun grenades, will also cause the Shieldbug to temporarily go "spastic". This means they'll turn and move in a random direction, even if there aren't any Marines there. This exposes them to the entire squad's firepower.
- Using the Flamer or Incendiary Sentry to set the Shieldbug on fire will inflict the fire "burn" effect, which can help wear its health down.
- Similarly, using Freeze Grenades or the Freeze Sentry will render the Shieldbug immobile and incapable of attacking, allowing the squad to flank it and bring all their firepower to bear on it. A chainsaw will quickly shatter a frozen shieldbug.
- Deploying one of your Incendiary Mines and luring the Shieldbug over it will instantly kill it. Remember - you can roll past the incendiary flames without receiving damage.
- During the Deima Surface Bridge end run, the Bloodhound's underbelly turrets provide much-needed firepower for taking care of the Shieldbugs there. Make sure you stay near the dropship's light and get the Shieldbugs to turn their back to the dropship. On lower difficulties you can just ignore the Shieldbugs to deal with the Drones - the Bloodhound will shred the Shieldbugs in a matter of seconds.
The Shield Down Achievement is awarded for landing the killing blow on a Shieldbug.