I was looking into something else when I found a little something on gant's, Fungus gnat's actually (not sure how many variety of gant's there are). I don't know if you are still having a problem with them or not, or even if these are the exact ones you have encountered. But it reminded me of this thread, and may be able to give you some ideas.
Fungus gnat - Wikipedia, the free encyclopedia
http://culturesheet.org/pests:fungus_gnats
Fungus Gnats, HYG-2114-95