What science fiction movie is this?

Quatermass and the Pit (1967)

aka Five Million Years to Earth

starring Andrew Keir, James Donald, Barbara Shelley, Julian Glover, Duncan Lamont, Bryan Marshall

IMDb synopsis:

Workers excavating at an underground station in London uncover the skeletal remains of ancient apes with large skulls. Further digging reveals what is at first believed to be an unexploded German bomb from World War II. Missile expert Colonel Breen is brought in to investigate, accompanied by Professor Bernard Quatermass. When the interior of the "missile" is exposed, a dead locust-like creature that resembles the devil is found. It is determined by Quatermass that these "locusts" are Martians who altered the brains of our simian ancestors to eventually lay claim to Earth. When Quatermass' suspicion that the missile can reactivate the dormant evil in humans is confirmed, all hell breaks loose.

WOW! I think YouTube might have the complete film! Here's Part 1:

http://www.youtube.com/watch?v=m54SmX15uS0

I'm definitely watching this right now!

I love this movie! You did a great job of describing it, especially the major scene of the man on the crane and the image of the demonic-looking creature towering above London.

Sounds like Bug from 1975 and starring Bradford Dillman

The bugs could start fires somehow