Enemies

Enemies are creatures that want to harm the player. They normally come from spawners and begin on the enemy force. There are three types of enemies: Biters, Spitters and Worms. Each of these types comes in three stages of growth and thus strength.

Achievements

Main article: Achievements

Enemies are directly connected to the following achievements:

It stinks and they don't like it

Trigger an alien attack by pollution.

Steamrolled

Destroy 10 spawners by impact.

Creatures

Biters

Biters are one of two main antagonists in the game. They are the native inhabitants of the extraterrestrial world and commonly live peacefully with worms and spitters. Biters are arthropods living in organic nests. They come in four sizes: small, medium, big and behemoth. In the beginning of each freeplay game there will only be the small ones, with increasing pollution they will become bigger, related to the enemy's evolution. Biters are attracted by and enraged by pollution and will attempt to destroy its sources. They prefer to attack the player character, turrets and radars and will stop searching for pollution if they can see and attack any of those. Biters deal physical damage.

Picture	Name	Info
File:SmallBiter-anim.gif	Small Biter	Weakest of biters, can be easily killed with a pistol. Health: 15 Damage: 6 Damage Type: Physical
File:MediumBiter-anim.gif	Medium Biter	Stronger and slower than the small biter. Can pose a problem for and even kill weaker players. Health: 75 Damage: 15 Damage Type: Physical Resistances: Explosion: 0/10% Fire: 0/-50% Physical: 4/0%
File:BigBiter-anim.gif	Big Biter	Very resistant and dangerous, nearly immune to gunfire. Can attack through walls and hit objects directly behind them. Health: 375 Damage: 30 Damage Type: Physical Resistances: Explosion: 0/10% Physical: 8/0%
File:BehemothBiter-anim.gif	Behemoth Biter	Very resistant and dangerous, nearly immune to gunfire. Can attack through walls and hit objects directly behind them. Health: 5000 Damage: 100 Damage Type: Physical Resistances: Explosion: 10/20% Physical: 8/20%

Combat

The biter class enemy will likely be the most common threat to a player's factory. While any attack can catch an undefended factory off guard, most players will be able to handle attacks from small biters with relative ease. Medium biters often pose a much greater threat due to their heavy armor. Big biters are another step in this direction and can come as another nasty shock to any player not familiar with their world's evolution level. Behemoth biters are a big threat to any factory and serve as the Player's prime incentive to avoid excess pollution. However, Biters of any size can be managed by static defense, though some of the larger waves can be overwhelming.

Biters come fairly early to attack a factory that produces large amounts of pollution, as pollution will attract an attack. Once the pollution cloud reaches a nest, the player can expect biters to be showing up shortly. The attack group will be focused on destroying the source of the pollution, but will change targets as soon as one appears of higher priority, typically by level of pollution, though they target the player or static defense first and foremost. Biters also have the ability to find their way around a defense, to a degree. This can be used to partially control the movement of the biters allowing turrets to damage them for a longer time, but requires the "bait" of this trap be left open. Biters aren't always willing to fall for the bait. Some biters will choose the most direct route and will attack the walls of the trap regardless making them less predictable and more dangerous.

Spitters

Spitters are much like Biters. The only difference, besides their appearance, is that they only have a ranged attack. They spit at any opponents (e.g. players) with an acid projectile that can neither be dodged nor deal damage to anything else than the original target. Commonly the acid resistance of buildings (like a turret) and armor is much lower than its physical resistance. Because of this Spitters deal more average damage than Biters. Their behavior and sizes are very similar to the Biters, except their health and resistances.

Picture	Name	Info
File:SmallSpitter.png	Small Spitter	Weakest of spitters. Easy to kill with any weapon, but attacks at range. Health: 10 Damage: 10 Damage Type: Acid
File:MediumSpitter.jpg	Medium Spitter	Stronger and slower than the smaller version. Can pose a problem for and even kill weaker players. Attacks at range, making it dangerous for turrets. Health: 50 Damage: 20 Damage Type: Acid Resistances: Explosion: 0/15%
File:BigSpitter.png	Big Spitter	An even bulkier spitter and so can take more damage. Attacks at range, making it dangerous for turrets and the player. Health: 200 Damage: 30 Damage Type: Acid Resistances: Explosion: 0/30%
File:BehemothSpitter.jpg	Behemoth Spitter	The bulkiest of the spitters and so can take even more damage. Attacks at range, making it dangerous for turrets and the player. Health: 2000 Damage: 50 Damage Type: Acid Resistances: Explosion: 0/35%

Worms

The Worms are natural allies of Biters and Spitters and will attack the player if they get close enough. They act like static turrets and will not follow you, they will instead use their much greater range, in comparison to other enemies, to inflict damage without leaving the nest. However, their static nature does render them more vulnerable to certain attacks.

Like any other enemy, worms come in 3 sizes, their power increasing with size. Unlike Biters and Spitters, Big and Medium Worms can be created directly after start of a new game, and will not always spawn near spawners. Their appearance is not dependent on time, however their appearance frequency can be modified by distance from the initial player spawn point, with greater distance yielding bigger/more worms.

Picture	Name	Description
File:SmallWorm.png	Small Worm	A weak worm. Still not easy to kill though. Health: 200 Damage: 10 Damage Type: Acid
File:MediumWorm.png	Medium Worm	Medium worms are very dangerous to even more advanced players. They should be handled with care. Health: 350 Damage: 30 Damage Type: Acid Resistances: Explosion: 5/15% Physical: 4/0%
File:BigWorm.png	Big Worm	Big worms are the most powerful enemy in Factorio. They deal a high damage and are almost immune to common gunfire of any sort. Health: 500 Damage: 60 Damage Type: Acid Resistances: Explosion: 10/30% Physical: 8/0%

Picture	Name
	Worm's animation

Big Worms Now Show Up In Early Game

Spawners

The homes of biters and spitters. While spawners themselves are generally defenseless (Unless a worm is nearby), the enemies they release overtime effectively serve as a form of guards to distract the player and any nearby turrets. If a group of enemies of the same variety is given the opportunity, they will automatically combine into a new spawner, expanding enemy bases.

Spawners exposed to pollution will use it to evolve the enemies they spawn, which may also result in an attack. Further away from the starting location the chances that stronger enemies spawn is higher. This is controlled by the spawn_shift; the higher the value of it, the higher the probability that stronger enemies spawn.

Spawners are effectively 'bullet sponges' capable of absorbing a large amount of damage. Explosives, shotguns, flamethrowers, and tanks are effective weapons against spawners.

Spawners are the only place to acquire alien artifacts, which are needed to create alien science packs, which in turn are needed to research late-game technologies. As of 0.15, alien artifacts were removed, meaning it is only beneficial to destroy spawners to clear out space or prevent incoming attacks.

Picture	Name
File:Biternest-anim.gif	Biter's Nest	Health: 350 Resistances: Explosion: 5/15% Physical: 2/0%
File:Spitternest.gif	Spitter's Nest	Health: 350 Resistances: Explosion: 5/15% Physical: 2/0%

Expansions

Every 4-60 minutes, a group of 5-20 biters will leave their base to create a new base. This group will search for a suitable spot that's at least 3 chunks and at most 7 chunks away from existing biter bases. Once they have found a suitable spot the group of biters dies and forms a new base. This new base will first be very small (about one spawner and a few worms) but will get some additional spawners within a small area as time passes.

Evolution

Spawn chances of biters from biter spawners by evolution factor. See the table below for exact values.

Spawn chances of spitters from spitter spawners by evolution factor. See the table below for exact values.

The evolution factor is a global variable that determines what kind of biters will be spawned. You can check the variable in the dev console via the following command:

 /evolution

It goes from 0 (not evolved at all) to 1 (maximal evolution). At the moment the evolution factor can only increase. The evolution factor is increased by three kinds of events:

Methods of increasing

• The passage of time very slightly increases the evolution factor.
• The global pollution production increases the evolution factor.
• Destroying enemy spawners significantly increases the evolution factor.

All these values are set in game.map_settings.enemy_evolution. From there they can be changed or modded.

The current (as of 0.14.22) default settings are:

Percentual Increases:

Source per	Variable in enemy_evolution	Percent increase
Tick	time_factor	0.0004%
1000 Pollution Units	pollution_factor	0.0015%
Destroyed enemy spawner	destroy_factor	0.2%

Pollution production is the total pollution produced by buildings per tick, not the pollution spreading on the map, so it is not reduced by trees or other absorbers. e.g. : 15 burner mining drills produce 150 pollution per second, raising the evolution factor by 0,00000225 per tick.

The percentages are applied on the base of 1 - current_evolution_factor. So for instance destroying enemy spawners in the beginning of the game results in increase of evolution factor by 0.005 (half a percent) while doing this when the evolution factor is 0.5 the increase is only 0.0025 (quarter a percent).

Besides choosing what kind of biter will be spawned the evolution also influences the spawning interval. This interval (spawning_cooldown in the enemy-spawner definition) is interpolated between 360 (0 evolution) and 150 (1 evolution) ticks.

Spawn chances by evolution factor

	Biter's Nest
Factor	Small Biter	Medium Biter	Big Biter	Behemoth Biter
0	100.0%
0.05	100.0%
0.1	100.0%
0.15	100.0%
0.2	100.0%
0.25	100.0%
0.3	100.0%
0.35	71.25%	28.75%
0.4	50.0%	50.0%
0.45	33.75%	66.25%
0.5	20.0%	80.0%
0.55	7.6%	79.8%	12.6%
0.6		79.0%	21.0%
0.65		62.5%	37.5%
0.7		38.25%	61.75%
0.75		33.5%	66.5%
0.8		29.5%	70.5%
0.85		26.25%	73.25%
0.9		24.0%	76.0%
0.95		16.25%	58.75%	25%
1		12.5%	50.0%	37.5%

	Spitter's Nest
Factor	Small Biter	Small Spitter	Medium Spitter	Big Spitter	Behemoth Spitter
0	100.0%
0.05	100.0%
0.1	100.0%
0.15	100.0%
0.2	100.0%
0.25	100.0%
0.3	41.25%	58.75%
0.35		100.0%
0.4		100.0%
0.45		100.0%
0.5		100.0%
0.55		66.0%	11.5%	22.5%
0.6		39.5%	39.5%	21.0%
0.65		17.5%	53.75%	28.75%
0.7			65.0%	35.0%
0.75			55.00%	45.0%
0.8			45.0%	55.0%
0.85			35.0%	65.0%
0.9			23.75%	76.25%
0.95			16.25%	58.75%	25.0%
1			12.5%	50.0%	37.5%