How do biters attack?

[Gazz]

In my first game they largely ignored me... until they sent one raid of 20+ big ass bugs that turned my entire base to rubble.
2nd game I am constantly being harassed and lose chunks all over my base. I'm struggling to build enough turrets/ammo/walls and it's war from the start.

So how DO they attack? Are they coming from a nearby base that is within the range of pollution so I should take out that base?

First game I got the tank and started taking out a bunch of bases in the vicinity and the enemy strength ramped up like 20x as a result of it, flattening my entire base before I could get back to it.
I don't understand if taking out these enemy bases is helping me or suicide. =P

[jagholin]

You are correct, biters attack from within your pollution cloud. So clearing out biter nests that your pollution is reaching is one common form of pest control.

On the other hand, destroying nests increases evolution factor rapidly(by how much, depends on your map settings). You can check the current value with "/evolution" command. Evolution can be between 0 at the start of the game, and 1.0 (asymptotically approaching this value, but never actually reaching it). There are a couple of milestones in this progression, where new biter types appear:

0.2 - first appearance of medium biters
0.25 - spitters start spawning
0.5 - big biters appear
0.9 - behemoth biters.

You can read more in the wiki: https://wiki.factorio.com/Enemies#Defense

[Scipione]

Best is you press "m" and have a look at the map, on the right side you can push buttons for additional informations, on of these buttons shows you, your pollution cloud.

Be sure to see everything on the map before the pollution cloud gets there and clear all nests before this cloud reaches them atleast until you have proper defenses set up

[Fel]

There are three things that trigger attacks.
First is proximity, if you are close enough to a group, it will attack you. This includes groups that were travelling, be it to expand or to attack. It also works for turrets.
Second is damaging a spawner, the whole nest's group will attack you and the spawners will spawn new ones relatively quickly to replenish the force (this is what makes attacking a large nest tricky, on top of the worms).
Third is when pollution reaches a nest, spawners will absorb it and create an attack force that will then head towards whatever produces the most pollution nearby and try to destroy it as well as whatever is nearby.


The enemies that spawn depend on what is called "evolution", it goes up based on time, pollution produced and spawners destroyed.

The wiki page on enemies is pretty detailed, if you want more specific informations:
https://wiki.factorio.com/Enemies

[Gazz]

Thanks. So whether to attack nests or not is a clear yesn't. ;)

[Fel]

Well, clearing the nests mean that they won't be able to send attacks from there, which means you don't have to spend resources on ammo/power to defend against the waves they would send.
Since it increases the evolution though, you typically only want to clear the nests that are close to your pollution (or already in of course) as well as the ones where you want to make mining outposts (soon to be in pollution as well anyway).

[jagholin]

Another tactic that you can use when you feel you are starting to get overwhelmed: shut down your factory( can be done in multiple ways, just stopping research/rocket construction is a simple option, more aggressive option is to kill off power)

No production means no pollution, whatever pollution cloud you have remaining will quickly shrink as it is consumed by environment(trees, green tiles). Biter attacks will also seize shortly after and you will have more time to rebuild/upgrade your defenses.

[Ozone]

Another thing that wasn't mentioned is biters are attracted by radars and substations. They will focus their attacks on them most of the time. You can also use this knowledge to lure them into a trap. But the biters aren't stupid, and they learn your strong and weak spots through tries and retries.