An Alien siege worm is in my city boundaries, destroying improvements one by one

[Leathaface]

I'm on turn 81 on Epic speed. There's not a single thing I can do because my city attack does barely any damage, it would be suicide to sent my marine after him.

Superb.

 

[Sprenk]

Build an Ultrasonic Fence, pronto! If you can't do that, all you can do is let the Worm play around a bit, and then clean up the mess after he leaves. Worm poop is so, so smelly.

 

[3 EMS]

How far away are you from being able to build that thing that keeps aliens two tiles away?
Don't try TACJETS. You think your marine is weak, those things are worthless against worms.

I'm on my first attempt but I would try that fence or force field. Then maybe a ranged unit.
I left the aliens alone early because I was no match for them.

 

[bkn42]

You have a unruly, ugly neighbor worm trespassing on your lawn?

I shall call him Justin Bieber.

 

[Eagle Pursuit]

Build the fence and some Rangers. Let the Rangers sit inside the fence and take pot shots at it until it leaves or you kill it, which will take several turns. At least killing it gives you a nice reward, if you have the quest.

 

[Callonia]

All you need is one ranger to kill it. It might take you like 40+ turns but you can do it with just one ranger. Its movement is 1. Ranger has firing range of 2 and movement of 2 with no setup time. Otherwise spam alot of rangers until it dies. xD

 

[mnf]

You want to at least kill 1 worm in your game for the quest reward of some yields. Obviously it doesn't have to be so early, but keep that in mind.

 

[MithrilSoul]

Another option defensively, besides the fence, is to get Purity level 1 (which makes explorers immune to aliens) and build about 3 explorers and use them to "wall off" your territory from the worm. Since the worm only moves 1 hex per turn and your explorers move 2, you can always keep them in proper position.

 

[NyQuil]

What's interesting is that I did kind of a hail mary on a prime area that was infested with alien life (including a worm) and the AI factions were unable to get close enough to pop an outpost.

I basically sacrificed a bunch of rovers to get my colonist in position and then poof, the outpust pretty much made all the alien life and the worm move back a fair distance.

I'd noticed they aren't very aggressive against new outposts and colonies so it gave me the time to develop around it and pop a fence in as soon as it hit colony stage.

Not sure if that's standard behaviour.