Overview
So you’ve just landed on an alien planet, beware you are not alone, the creatures on this planet want to kill you. In order to be prepared, you must learn about your enemy and what sets them off. (after all, knowledge is power) This guide will cover what strange creatures are on this planet and how the pollution from your factories (Yes yours…) will attract unwanted pests and even make them stronger. This will contian information geared towards new players but will have some information that will be helpful to advanced players alike.
Pollution Mechanics
Pollution is a core concept in Factorio.
Pollution is produced by basically any building that is involved in the extraction or production of materials. You can see how much pollution buildings produce by hovering your mouse over the building. The number shown on the building indicates how much pollution is produced, per second, when it is at full power.
This pumpjack produces 9 pollution per game second at full power
Spread of Pollution
Every second, all of the pollution produced in a chunk (an area of 32×32 titles) is added together. Once the pollution produced is greater than 15, it will spread out in all directions, except diagonally at a rate of 2% per second. For example, a chunk with a pollution of 100 will spread 2 pollution to the surrounding chunks and reduce the original chunks pollution by 8.
Absorption of Pollution
Similar to before, every second, certain entities reduce the polution in a chunk.
- All trees, alive or dead will slightly reduce the pollution in a chunk (different trees have different values of absorption)
- The ground of every chunk will slightly reduce pollution (different types of ground have different values of absorption)
- Spawners (will be discussed later) absorb the greatest amount of pollution per second.
How to see your Pollution
When in game you can get a rough estimate at how much pollution you factory has produced by turning on the alternative view mode. (by default the Alt key) This will show you how polluted the chunks are, with red indicating more pollution.
My second base aprox 35 hours in with alt view on
Another way to see the exact pollution values is by pressing f7 (or Fn f7 for macs), this will allow you to see the pollution values in map mode when zoomed on a chunk. (Press the key again to disable the mode)
Once pollution spreads to an enemy base, the base will start to send waves of biters and spitters to attack, the more pollution that spreads the greater the spawn rate and the stronger the enemies that are spawned.
The Enemies of Factorio
While it can be argued that you are the enemy for polluting the environment, stealing the planet’s resources and killing the indigenous population, for all intents and purposes of this guide, the native life are the bad guys. Luckily for you, the native life on the planet have banded together to destroy you and your factories.
All of the native life on the planet can evolve and become stronger over time, this section will cover all of the types of enemies and their forms.
Biters
Biters are on of the main species on this planet. They spawn from the beggining of the game and can pose a threat early on to unprepared players. They can only attack via meele and thus are easy for turrets to deal with when there is a wall infront of them.
The four tiers of Biters are:
- Small Biter
Quick and agile,small, brownish colour, exist from the start of the game.
Health: 15
Damage: 6 - Medium Biter
Health: 75
Damage: 15
Redish, exist only at .35 evoloution and above. - Big Bitter
Health: 375
Damage: 30
This is the time to be cautious, high health, hard to take down. Exist only at .65 evoloution and above. - Behemoth Biter
Health: 5000
Damage: 100
Noting to shake stick at, will kill you FAST Exists only at FULL evoloution (1)
Spitters
Spitters are the other main species you will encounter on the planet, just as the name suggests, they fire a “spitball” at a ranged distance that cannot be avoided. They are a hazard to turrets as they can fire over walls and destroy turrets. Also attracted to pollution. Follow a similar pattern to biters.
The four tiers of Spitters are:
- Small Spitter
Health: 10
Damage: 10
Not availible from the start of the game, .3 evoloution to .65. - Medium Spitter
Health: 50
Damage: 20
Exist from .55 evolouton and above. - Big Spitter
Health: 200
Damage: 30
Exist from .65 evoloution and above. - Behemoth Spitter
Health: 2000
Damage: 50
Will snipe you down from across the map Exists only at FULL evoloution (1)
Worms
Worms are static and are found around enemy bases, they act like turrets and will attack via ranged attack if you get too close. If you are not in range they retract and hide in their hole. Unlike Bitters and Spitters worms are not tied to an evolution scale.
The three tiers of worms are:
- Small Worm
Health: 200
Damage: 10 - Medium Worm
Health: 350
Damage: 30 - Big Worm
Health: 500
Damage: 60
Very resitant to regular gun fire, deals high damagem beware.
When no enemy in range the worms return to their hole.
As time progresses, the enemy bases grow, to seemingly massive sizes that make them quite hard to destroy.
Over time the bitters and spawners will spread out to form a new base, the new location will be at least 3 chunks away from the players base and their original base.
Evoloution in Factorio
Evolution is a numerical value that decides what types of enemies are spawned in the world. It starts off at 0 and has a max of 1.
The evolution factor can increase in 3 ways:
- Every tick evolution increases by .000004 (or .00024 a second)
- For every 1000 pollution created, evolution increases by .000015
- For every enemy base destroyed, evolution increases by .002
As you can see destroying enemy bases greatly increases the evolution level compared to the increase in time and pollution created.
There is no way to decrease evolution, so plan ahead!
You can check the evolouton progress in the dev console (default “/” or “~”) and entering “/c game.local_player.print(game.evolution_factor)“
As stated in the previous chapter, only certain enemies exist during certain evoloution periods. In addition, there are differenct chances different enemies will spawn at varying evoloutions. 
To the left are the chances of biters spawning and above are the chances of spitters spawning
In Summation
Thank you for viewing my guide, I hope it has tought you some new things, if you have any questions or suggestions for new topics, leave them as a comment or message me and ill try to help out!