I think it's a 90s movie. It's about a scientist who studies insects. The scientist has tons of insects in the apartment. Somehow a weird species develops and ends up living and reproducing in the subways. They are large and smart and try to kill the scientist and the a little boy ( I forget how the little boy comes into play)

I believe Mimic (1997) - IMDb (http://uk.imdb.com/title/tt0119675/) is the one you're looking for. Excellent film! Mimic 2 is pretty good as well, haven't seen 3.

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