Martian (The Angry Red Planet)

  Men of earth, we of the planet Mars give you this warning, listen carefully and remember. We have known of your planet Earth since the first creature crawled from the primeval slime of your seas to become Man. For millennia, we have followed your progress. For centuries, we have watched you, listened to your radio signals and learned your speech and your culture. And now, you have invaded our home. Technological adults, but spiritual and emotional infants. We kept you here deciding your fate. Had the lower forms of life of our planet destroyed you, we would not have interfered. But you survived. Your civilization has not progressed beyond destruction, war and violence against yourselves and others. Do as you will to your planet, but remember this warning--do not return to Mars. You will be permitted to leave for this sole purpose--carry the warning to Earth. Do not come here. We can and will destroy you, all life on your planet, if you do not heed us. You have seen us, been permitted to glimpse our world. Go now. Warn mankind not to return unbidden.   The Martian message to Humanity

Martians are an insectoid race from the planet Mars, they seem to be quite unpleasant towards guests.

Biology
Not much is known about Martian biology, they are known to have three eyes placed in a triangular position on their neckless torso, they have two antennae and what appears to be arms.

Technology
Martians appear to be sufficiently advanced, having large cities and force fields

History
Martians have existed since before the development of Multicellular life on Earth, when Humans eventually did evolve, the Martians studied them and listened to their radio signals, learning Earth culture and languages, when a human vessel arrived on their planet, they held it with one of their forcefields hopping that they native fauna of their world would take care of the issue, when the Humans survived, they allowed them to leave but made them return to Earth with a message to never return to Mars.