To clarify, all of San Diego County is classified as having a desert climate. However, it is nothing like, say, the high desert where DW went on his MH trip. It is a very dry, mild climate. Temperatures in the winter, at night, will get into the 30's in some areas. A shift of 10 miles either way usually brings the temperature up or down. But, we are no means living in the typical "desert" that people may be associating the Dehesa area with.
Semi-arid at worst, and even true deserts like Phoenix and Las Vegas, have plenty of flies let me tell you.
Because VRWC_minion has an idea that flies are different in "the barren desert", whatever that means.
It would screw the theory if :
A. flies are the same all over.
B. El Cajon is not desert.