In the book "The Mote in God's Eye", by Larry Niven and Jerry Pournelle, the humans are forced to evacuate one starship due to it being overrun by the rapidly breeding Watchmaker caste of 'Moties'.
The Engineer class Motie they had captured simply opened his ship to vacuum to get rid of Watchmakers, keeping only one breeding pair.
In their look around the Motie world the human party noticed several main classes of Motie on the crowded streets but there wasn't noticeable crowds of Watchmakers.
It's been a while since I read the book, was there an explanation given for the comparatively low numbers of Watchmakers on planet?