I'm looking for a story which has these elements: There is an alien species whose biology compels it to reproduce every couple of years, and they don't have a choice about it. As they develop technologically, the population rises faster and faster until civilization falls again and a period of darkness comes to the world. They try various ways to prevent it - drugs, infanticide etc, but they've never been adopted by the whole world, so civilization keeps rising and falling. There is also some mention of different varieties of the aliens - soldiers, medics, etc. and perhaps trying to eliminate certain versions to reduce the population pressure.
The story takes place during a period of high technology. The main characters stumble on an ancient subway line which has somehow survived.
I read it in the 90s, but it could have been written quite a while earlier.