I have a riding buddy that is an entymologist. He says that bugs have a unique property included in many of their genes (DNA). Saliva Propelling Invading Trait and Homing Device is the official term, or SPIT Homing Device. Most bugs not only aim for the mouth, but they are helpless to avoid the impending death. Some of the higher developed species will try and fight the urge, but most cannot help alter their flight path. Some can be heard to scream just before entering the "mouth of doom" which is similar to an early warning device. So, if you hear tiny, terrified scream directly in front of you, turn your head immediately.
In the long run, I have (at a nominal fee to you) devised a anti-SPIT Homing Device that will thwart the little buggers. These are on sale for $24.95 (US) and for a limited time only I will throw in a set of carbon steak knives.
E-mail me at http://www.imafool.com