Woah! Those little Shits can dig UNDER cover!" — Damon Baird when first encountering the Digger Diggers were small burrowing creatures enslaved by the Savage Locust for use as explosive projectiles that are fired from the Digger Launcher. When fired, they burrow under the ground behind cover, then pop up and explode in the air, killing the enemies in that cover. They can burrow through dirt, rock and wood.
When fired into a target, the digger will latch on to the target and chew into its chest before exploding inside the victim.
Destruction of Halvo Bay, Locust General Karn attached some kind of Digger Launcher to Shibboleth's prosthetic leg, way before anyone else used such a weapon.
Flooding of the Hollow, Boomers were left to wander around the surface without their trusty Boomshot Grenade Launchers. They eventually harnessed Diggers and created the Digger Launcher, which was similar to Karn's in design.
Cliff Bleszinski has commented that "If you listen closely, as the Digger is heading for you, you can hear it say "Nom nom nom nom nom."  Like the
Bolo Grenade, the digger beeps before exploding, give the player half a second to roll away. The Digger will latch on to the enemy and chew him or her to death and explode, in multiplayer or single-player campaign mode.
↑ Comic Con July 23, 2010; Gears of War 3 Q&A
Hollow and Enemy Creatures
( Berserker Matriarch) · ( Boomer Butcher, Flame Boomer, Grinder, Mauler, Mauler Elite, Savage Boomer, Tremor) · ( Drone Beast Rider, Bolter, Cleaver Theron, Cyclops, Disciple, Flame Drone, Flame Grenadier, Grappler, Grenadier, Grenadier Elite, Gunner, Hunter, Hunter Elite, Miner, Palace Guard, Rager, Savage Drone, Savage Grenadier, Savage Grenadier Elite, Savage Hunter, Savage Marauder, Savage Theron, Sniper, Spotter, Theron Elite, Theron Guard, Theron Sentinel) · ( Kantus Armored Kantus, Savage Kantus, Zealot) ·
Bloodmount · Brumak · ( Corpser Shibboleth) · Digger · Gas Barge · Heart Leech · Kraken · Kryll · Leviathan · Mangler · ( Nemacyst Ink Grenade) · Nemacyte · ( Reaver Assault Barque, Hydra) · Riftworm · Rockworm · Seeder · Serapede · Siegebeast · ( Tempest Shrieker) · Ticker · Torture Barge · Wretch
Former · Lambent Berserker · Lambent Brumak · Lambent Bull · Lambent Dog · ( Lambent Drone Lambent Drudge) · Lambent Gunker · Lambent Leviathan · Lambent Polyp · Lambent Stalk · Lambent Wretch
Canker · Carrier · ( DeeBees Bastion, Reject, Stump) · ( Drone Elite Drone, Grenadier, Elite Grenadier, Hunter, Elite Hunter, Imago, Sniper, Elite Sniper) · ( Flock Leech) · Hive Beast · ( Juvie Screamer, Popper) · Kraken · Locust Drone · Matriarch · Pouncer · ( Scion Armored Scion, Heavy Scion, Scion Elite, Warden) · Sire · Snatcher · Swarmak
DR-1 · ( Shepherd Deadeye) · ( Tracker Shock Tracker) · ( Watcher Guardian, Sentinel)