Maybe I missed something when Rita and Dr. Carter explained things to Cage but if I remember correctly, they said the Red Mimics were common drones and are like claws, the Blue Mimics (Alphas) were the central nervous system and the Omega is the brain.
I'm wondering, other than using this for the plot of the movie, why does the alien even send out the blue Alphas out to fight and risk transferring the time resetting power to a human? Wouldn't it be better to only use the Red Mimics to fight and not worry about transferring this power to a human who can then reset time? What was the reason to have blue Alphas fighting?