Interesting enough, while tracking down the studies that DEET actually does repell insects, not just jam/numb them, they indicated the same receptors also detected other undesirable plant aromatics like eucalyptus etc. I'm guessing that when it's not breeding season and the females need blood protein to lay eggs, they all go after plant juices instead and that sense protects them from trying to tap plants that are caustic or poisonous to them.
Which might also be why Citronella works. (sort of...) The D-Limonene component is toxic to insects, because it dissolves the lipids and waxes that keep their chitin parts waterproofed to keep their organs and fluids inside.
If I can find suitable sources for these, I might work up a cocktail that's more potent than DEET alone.
