In Freeplay you can enable Funnelweb Spiders, these spiders make it hard to have a line of ants as they pick off anything that isn't a Major. Only problem is, they never despawn even if you kill the spider's replacement that replaced the replacement.
Perhaps after a spider has been killed 3 times, the "nest" gets destroyed or Major's can be ordered to destroy it (slight problem for Black, Wood and Fire Ants though)
Perhaps after a spider has been killed 3 times, the "nest" gets destroyed or Major's can be ordered to destroy it (slight problem for Black, Wood and Fire Ants though)