Add some very useful buildings to combat the Enemy threat, as changed by N.E. Enemies and other mods that increase Enemy difficulty. Please visit home page for more details.
My question is, do tamed aliens expand by creating their own spawners and/or worms?
And do they automatically form groups and attack enemy aliens and their bases?
I don't really know the answer if they expand by themselves. I've not seen it, but don't know....
You can control the aliens by using the "alien_training" technology. It gives you a little remote. If ON they will follow you.
Or, even better, install "Unit Control" mod by Klonan and use that. https://mods.factorio.com/mod/Unit_Control