Factorio Forums

I know that pollution is absorbed by nests and used to create biters/spitters so they can attack the source of pollution.

However, if you kill the bugs around a nest, even in an area where there is no pollution those biters and spitters seem to still respawn to defend the nest.

The question is do the nests replace their defensive troops for "free", meaning those particular defensive bugs don't require/absorb pollution?

short answer: yes, for free... meaning they don't necessarily need pollution. The wheel still turns.

Thank you for the reply! I have to be particularly careful not to build near biter bases in my deathworld marathon game as the outposts constantly trigger the biters in the bases and those free biters are eating up my ammo supply so much so I need to go back and try it again.

Killing biters doesnt affect evolution.

The nests gather pollution and "pay" with the pollution to send an attack.
Destroying nests increases evolution.

If you can handle the attacks you might want to keep the nests in place. The pollution is sucked up by these nests and doesnt spread further.
On he other side the attacks cost you resources that must be reproduced.

A small part of my map Marathon of the World of Death.
Very late game
On the left, you can clearly see the biter
Red are nests.
Green - the area on which they respawn and settle with some probability.
Therefore, long-range guns are often installed along the perimeter, to shoot the newly created nests.

No one is recommended to play in the Marathon with such pollution)
Only if there is very good protection and defense