Start travelling from West Europe towards East Europe. Until you reach Romania/Slovakia/Serbia/Ukraine, your car is clean.
Over these borders, after 10km of night ( or even day) drive your car will be splatted with insects. No idea why, but the vegetation is incredibly varied/wild compared with West Europe.
Slovakia here. Not sure about the eastern part of our country as I don't travel there very often, but as for the western part, we are fully integrated into the ecological disasters of western Europe. Meaning almost no insects this summer. Even mosquitoes were far from their usual numbers.
That sounds like the boundary between the regions where herbicide/insecticide is economically viable and where food prices are low enough that it's not worth it.
I drove 400 miles in Florida at all times of day and night between Daytona Beach and Tampa, including a couple national parks along the coasts, and I only had about 2 bug splatters.
But the mosquitoes north of Cape Canaveral were on to me the moment I got out to take a short hike.
Did similar driving Eastern Kansas/Western Missouri below Kansas City, and no bug splatters. Doesn't matter time of day, traffic, countryside, just nothing.
The water north of the Cape is called the Mosquito Lagoon for a reason...
If you want to see serious bug splatters, try Okeechobee during love-bug season. I drove through that once about eight years ago, and the marks are still visible on the car.
