Sheegupt

Allegedly, the Sheegupt were a sapient, space-faring species of the Milky Way Galaxy. It's not clear whether they ever existed at all, but if they did, they are long extinct by now.

Biology
Their biochemistry was based on carbon, water and oxygen, not unlike that of Humans or Chirpsithra. Unlike these, however, the Sheegupt evolved on a world orbiting a bright, F-type star.

History
When they first contacted the Chirpsithra, the Sheegupt were a race of missionaries, out to spread their pantheistic religion. The two races didn't get along then. By the time contact was made again, some hundreds of years later, the Sheegupt' religious beliefs had collapsed and they had become mostly agnostic. They became close allies of the Chirps and both species traded peacefully.

Slowly, the Sheegupt turned their attention to the idea of scientifically testing religious concepts. They made experiments to attempt to extrapolate other universes, the nature of God and attempted to contact the dead. At one point, some kind of breakthrough was made, but then communication stopped and the Chirps heard nothing further from them. When they sent vessels to the Sheegupt planets to investigate, they found out that the entire race had committed suicide en masse.

Every Chirpsithra group which studied the last reports made by the Sheegupt scientists also ended up killing themselves, until finally, the results were destroyed. Whatever it was that the Sheegupt found out about the afterlife will remain unknown.

Appearances

 * "The Subject is Closed", by Larry Niven (1977)