I thought I'd add a couple of things about the film Mimic.
I watched it, by coincidence, around the same time as I was reading The Mole People and was struck by parallels between the book and the film.
The Mole People is about homeless people living in tunnels underneath New York City, while Mimic is about giant insects who pass for human in the subways. There are some extraordinarily powerful scenes in the film, like when the insects' colony is found, all these creatures that look like men in overcoats are seen hanging from the ceiling of a densely crowded cave.
The most memorable aspect for me is the other bit of mimicry in the film: a little boy becomes obsessed with the creatures, who pass into and out of the world above through a portal located in a building opposite the boy's house. He has learned how to mimic the sound the creatures make and has christened one of them Mr. Funny Shoes.