The Breach - S2-E21
Corrected entry: How in the heck someone like in Doctor Phlox's time frame knew anything about tribbles in the first place. It was 100 years before McCoy and Cerino Jones and 200 years before Worf and co. Guess Doctor Phlox can leave a note to Doctor McCoy about the tribble's life cycle and its predators.
Correction: Dr. Phlox is an xeno-biologist from another world - his whole life's work is to study all life on other planets. He has many creatures living in the Sick Bay that I'm sure Dr. McCoy has never heard of. Dr. McCoy is a medical doctor who knows how to treat humans (and a few aliens), not a biologist - there are probably lots of Earth creatures Dr. McCoy couldn't tell you the life cycle of. No one could possibly know the life cycles of all creatures on thousands of planets.
Myridon