If you watch a fly on, say, a coffee table, you'll see that they're rubbing their little legs together to groom themselves; they're actually quite clean creatures.
The robotic fly that we actually make the most use of in our laboratory is actually not a small thing, it's a giant thing. It has about a meter wing span, and it flaps in three metric tons of mineral oil. And it is a so-called dynamically scaled fly.
Like many insects, flies are most sensitive to green light. This means that they would see their world as 'black and white,' in that they can't see the multiple colors required to reconstruct a color image of the world. They do, however, have specialized cells that enable them to see ultraviolet wavelengths.
I'm obsessed with insects, particularly insect flight. I think the evolution of insect flight is perhaps one of the most important events in the history of life. Without insects, there'd be no flowering plants. Without flowering plants, there would be no clever, fruit-eating primates giving TED Talks.
When it first notices an approaching threat, a fly's body might be in any sort of posture depending on what it was doing at the time, like grooming, feeding, walking, or courting. Our experiments showed that the fly somehow 'knows' whether it needs to make large or small postural changes to reach the correct preflight posture.
Fly flight is just a great phenomenon to study. It has everything - from the most sophisticated sensory biology; really, really interesting physics; really interesting muscle physiology; really interesting neural computations.