The Scathos were an alien civilization. In their culture, any woman who had a baby before the age of 40 was to be executed.

The Doctor mentioned the Scathos' customs to Kes in 2371 as part of a "statistical survey" with which he thought Kes could use as a context to help her decide whether or not to have a child. (VOY: "Elogium")

This species was only mentioned in dialogue.