A counter to infestations that isn't guns or kill it with fire.

[doctercorgi]

They are bugs right? Big bugs but still bugs. How about pumping whatever room they are in full of pesticide? (Being able to pump gas into rooms like a super villain would be BaLLer). Or a sprayer weapon to spray poison at them or in their path. You could also put out poison food pellets. The reason I am suggesting this is that fire can be Op when dealing with infestations, unless they are in your storage area, and attacking them head on is difficult without good weapons and armor. For a colony with little resources, theres not much you can do about them.

[4myGod]

Perhaps something like the fire extinguishers.  You can prebuild insecticide vents around your base with a switch from outside.  So when you get an infestation you have to move all your colonists outside and poison the building, then wait for the poison to go away over a few days time.

[Mehni]

Here's a counter:

Build outside.