I didn't like them. I liked fighting other aliens but I hated the concept. They were a lame excuse for the aliens to fight each other. I don't know why Dr. Kadinsky would think his bioengineered aliens would be superior to normal aliens. They are not stonger, faster or smarter in any way and they don't have any unique abilities. In fact their bad AI makes them pitifully easy to defeat. They carry hosts right past your hive! The only difference is the color which would severely hamper their camouflage ability in a more realistic environment. A possible explanation that the K-Series could be controlled by humans is contradicted in the last mission where they are not under human control.