From the ‘all things Aliens’ sub-reddit /r/LV426:
“Imagine that Weyland-Yutani has a military contract for a bioweapon that can wipe out a population in a very short amount of time. They provide a specialized military unit a clutch of eggs (now engineered), including a queen, and a civilian handler who works for the Company.
Now, there are these rebels on some assbackward planet who don’t like how Earth is exploiting them. So they’ve taken control of the planet and it’s only now, after months of self-governance (since it’s so bloody far away), that they’ve become complacent; they think that they’ve won. Within a month, they’re all dead.
The clutch of eggs was brought into the city using a compromised supply shipment. The eggs infected the a few dockworkers and flee underground to became a hive. The hive begins abducting people from the city until it reaches a critical mass, then it begins attacking in large, organized raids. Hundreds become new Warriors and Drones every day. One hive becomes several. The independent colonists fight back, but they have no military hardware; only construction tools and light arms. Soon, there is no one left. Lacking the presence of the pheromones live human emit into the air, the hives become dormant, as per the creature’s engineering. A week later, the hive self-terminates; the queen dies and all of her subjects; any remaining eggs self-abort.
The army shows up shortly thereafter with flamers and cleans up. There’s some acid damage here and there, but what would have taken months, massive amounts of munitions, and dozens of human lives is over in mere weeks. The only reason the Marines didn’t invade personally is because the orbital guns were taken intact and there are highly defensible bunkers.”
Image is a screencap from Alien Resurrection