That's one way of looking at it. Real or not, if there's a lot of other humanoid, which is quite an egocentric naming move but understandable, than there's also the probability of there being multiple insectoid races out there right?
About the terrestrial mantids being evil I have to disagree. There's a field near me where at a certain time of the year several species gather to mate and it's really something amazing to watch them in huge numbers, a very rare occasion. I've studied them for many years and spent time with them. They're rather beautiful just like any other lifeform. If we take the premise that efficiency = beauty, then it holds even more truth. Genetically, moths are some of the most perfect creatures at the top of "evolution" in a totally non retarded Darwinian sense. Right below them are mantids, roaches, grasshoppers and a few other related groups. They're all marvelous little critters and can teach us a lot if we finally wake up to the potential of biomimetic technologies that can revolutionize our society once we're spiritually mature enough to go down that road.
As for the evil master of reptilians race story, I've heard of it too but consider it irrelevant to our plight here and choose not to pay any attention to such things.
Cheers
SWP