I don't think I will win so I haven't started the fight yet. People can only come to my settlement from the eastern location as this one time someone came from the north the horde got them. I don't think it is at all safe for any visitors to come from any other direction. The guy who was caught by the horde resulted in the bugs marching towards my base but they turned around for some reason just before any shots were fired.

I counted 92 megaspiders, I think I need at least 5 vulcan cannons before I can start the fight but getting the steel has made me scour all the adjacent areas. After about another year in the game I might be able to take them out. It has already been 3 years.