Penang is in the tropics so mossies are commonplace. And yes, what you heard is true, they don't bite the locals, only the tourists;p If you're thinking of escaping the mossies, going to the 850m-above-sea-level-Penang Hill might be a good idea. But be warned, there are other tropical delights there! I caught sight of a little green fella when I was there , sipping my tea in Bellevue Hotel* . If truth be told, Mr Snake looked pretty harmless but I left him alone to catch his siesta.
*There is a little sign in the garden that warns you of harmless pit vipers ( PIT VIPERS???!!) that live in the ivy-covered roof above the restaurant.