The Zerg (origin unknown) are actually composed of several different types of creatures ("breeds") which, while physically distinct and unrelated, seem to share a common psychology and sense of community. Although we have had only limited resources to draw upon--mostly sensor logs, eyewitness accounts, and expired subjects--the picture that we have created is a fascinating one. Perhaps the one thing that we do know is that the Zerg do not wish to coexist with any other species. They are extremely aggressive and almost cruel in their attacks and attempts to infest inhabited areas. Species that they encounter are either deemed useful to the hive and mutated, or eradicated.