Editorial Notebook; Life in the Information – New York Times
Commercials no longer sit still and beg to be looked at. Instead, they become fly-like robots that perch on the pillow and whisper sweet nothings while you sleep. The next morning you wake up craving foods you’ve never eaten. Mr. Dick’s characters defend themselves by keeping their windows closed — and making heavy use of fly swatters. The idea is to get them before they get to you.

I remember them from his books as gen-manipulated flies, that is bio flies (grown) rather than robotic flies (built).

They are still much bigger than flies, more like bats, but they are coming:

Inhabitat » The Solar Powered COM-BAT Spy Plane
In this season of specters and spooks, what could be scarier than a steel-winged robotic spy plane shaped like a bat? The aptly named COM-BATis a six-inch surveillance device that is powered by solar, wind, and vibrations. The concept was conceived by the US military as a means to gather real-time data for soldiers, and the Army has awarded the University of Michigan College of Engineering a five year $10-million dollar grant to develop it.