Lord of the flies

Every year around Autumn, thousands of fruit flies get swept up from fields on up-draughts and find themselves pinned against the Physics tower's top windows.

In the old days before we had air conditioning, these flies would frequently flock inside, necessitating an annual fumigation.

Thankfully, people have kept the windows shut and the swarms of flies are meandering about on the outside of the glass. There are thousands of them, it's very disconcerting!

How many words can you think of that begin with 'f'?