The Locust are technologically proficient, but prefer to use natural resources to the best of their ability. This is why their barges, blimps, and other "vehicles" are all powered by living creatures. They even have a symbiotic relationship with creatures like the Brumak and Corpser, using them not only in battle, but to aid in their subterranean terraforming efforts.
4. Animal Lovers Would Especially Hate The Locusts