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Bugs "splat" on flat surfaces like this grille, but they smear on inclined windshields.Flies are not the only insects found on car windshields. Mayflies, deer flies, mosquitoes, lightning bugs---millions of creatures have died instantly and spectacularly on the front windows of vehicles. They are more numerous at certain times of year and in certain places: If you drive down lots of two-lane country roads in early summer, you're sure to pick up thousands. Unless you drive through a swarm where bugs literally throw themselves at your vehicle, though, you're likely to find the deceased only on the front vertical surfaces of your car---the grille and the windshield. The answer to why these surfaces end up with all that gunk has two parts, one easy and one a bit more complex. -
A fly will only win a race with a car in a school zone.It may seem like common sense, but there really is research on how fast flies travel. The calculation is that a deer botfly (that nasty thing that bites in late summer) travels at about 10 yards per second--or 20 miles per hour. Deer botflies can't catch up with you even if you're driving at a town speed limit of 25 miles per hour. If they fly toward the front of your car, on the other hand, the impact is equivalent to a 55-mile-per-hour collision. In addition, most insects don't fly around running into huge steel objects by choice---their ability to avoid objects is necessary to their survival. An automobile going 50 or 60 miles an hour, though, is something that their radar picks up too late to be able to swerve to avoid. So just based on their abilities and behavior, flying insects are almost always likely to collide with the leading surfaces of the vehicle. -
Deflectors raise the air current to protect leading edges of hoods.Like liquids, air flows over, under and around objects. The front edges of a car in forward motion--its grille and windshield--catch air and the tiny bugs that are flying in it, forcing them up and around its body. The air currents carry the insects around the surface of the car like surfers on a wave.
Early, flat windshields collected huge numbers of bugs on summer evenings. In newer cars, as windshields were aerodynamically tilted back, bugs made long smears as they were dragged astern by the air flow. Bugs that arrive too early to ride the wave simply "wipe out" on the front surfaces of the vehicle as they divide the airflow. But bugs flying behind the car don't even get the chance to surf; rather than smack against the back window of your car, they'll hit the front window of the car behind you.
