Long-legged Fly

I have a hard time getting images of these real small flies. They seem to have the uncanny ability to sense when a flash is going to go off and take off between the time you press the shutter release and the time the exposure is made. This results in either a picture of where they were or them airborne and out of focus. Horse flies seem to have this ability, too. I suspect they must sense a magnetic field set up by the flash. The only solution I've found is to turn the flash off. I had use f3.2 to get this image, which resulted in a very shallow depth of field.