There's a glitch on the first challenge. If you were to put a pheromone marker away from your nest during the nonstop attacks (specifically near the trail), and then put the pheromone marker in the nest; There will be a small group of ants not going to the pheromone (Because the feeder soldiers are distracting them) and working their way up to the entrance of the feeder colony. They then will camp out for the rest of the mission and bottleneck them. This will be a LOT more common when you've made minor improvements to black ants because the black ants completely overpower the feeder soldiers. The second image is the improvements I used to cause this glitch.