Daydreams about the flight of insects

I just watched an insect outside my window hover and then zip away. I started thinking about how hard that would have been for a large bird. I thought about weight/mass differences. And I thought about internal versus external skeletons.

I decided that flying insects must have little or no muscle. But, I can't think of a mechanism which replaces muscle. Are their ligaments, is it all just nerves? Could it be?

Does anyone know how insects move?