How do enemies build bases?

[bobingabout]

I've been looking into starting to make extra enemies for my mod, one of the things I want to add is another biter spawner with different enemies in it, similar to how they added the spitter spawner in v0.11.
However, I see no code that could define what entities are spawned in the enemy base creation routines(enemies from spawners is fairly obvious), does anyone know how this works?

The only code I see about enemy base placement is the auto-place controlls, which as far as I know are for map generation, does this double up with base creation too?

[bobingabout]

It apears that Enemies do use the Auto-place controls to determine what to build when building a new base, this will require a little more looking into, but it means I probably won't be able to limit what they build based on Evolution factor.