The Marines though when asked what they were dealing with seemed Disappointed when they found out is was a "Bug hunt" Which implies they've encountered Nuisance Aliens before.
Regarding the Predator post. Maybe there's Sects or Caste? Within Predator Race? Similar to the Tau from Warhammer? Fire Cast do the Fighting aka the Predator Hunters etc. Then you have the Engineer Caste aka Earth Caste for Tau. This caste provides for the manufacturing, agricultural, industrial, artisans.