Seeing dead bugs on a windshield isn’t a welcome sight, but maybe it should be.

Seeing fewer of them is an anecdotal sign that bugs may be in trouble.

Dubbed the "windshield phenomenon," the term gained traction in 2017 following the publication of a PLOS One study about a 27-year decline in the bug population across protected wilderness areas in Germany.

It was used by university and amateur entomologists involved in the study to describe how the study got started.

"If you talk to people, they have a gut feeling. They remember how insects used to smash on your windscreen," Wolfgang Wägele, director of the Leibniz Institute for Animal Biodiversity in Bonn, Germany, told Science magazine in 2017.

But then people realized they were scrubbing their windows less often. Some folks chalked it up to cars becoming more aerodynamic, but as Martin Sorg, one of the scientists involved in the study told Science, "I drive a Land Rover, with the aerodynamics of a refrigerator, and these days it stays clean."

While this may sound like folks being nostalgic, it indicated to bug-watchers of all stripes that something might be going on with the insect population.

After analyzing insect traps across the 27-year period, researchers were unable to determine a cause — but the usual suspects of habitat loss, climate change and pesticides were all on the table.

Signs of an 'insect apocalypse'

Luquillo Forest Reserve Puerto Rico, declining bug populations The Luquillo forest region represents one of the oldest reserves in the Western Hemisphere. It's home to more than 200 species of trees and plants, some of which are found nowhere else — but bug populations are declining here, too. (Photo: USDA [public domain]/Flickr)

Windshields aren't the only places we're detecting fewer insects. A study published in the Proceedings of the National Academy of Sciences explained how a researcher who studied the diets of Puerto Rican lizards in the 1970s returned to his old stomping grounds in the Luquillo Forest Reserve during the 2010s and collected 10 to 60 times less insect biomass than he did 40 years ago.

That's 473 milligrams of bugs in the past compared to just eight milligrams in the present.

Not surprisingly, the decline of the insect population mirrored a decline in the lizard, frog and bird populations, all species that rely on insects for food. The study suggested that a global temperature increase of 2 degrees Celsius was to blame for the drop in insect numbers.

New studies around the globe have been rolling in with regularity, all with dismal headlines and more evidence pointing to an "insect apocalypse" threatening all ecosystems and all creatures. One of the latest, taking place in Kent in the United Kingdom, answers an earlier question about thermodynamics and the types of cars used in the studies. Researchers placed a grid over the front license plate — endearingly called the "splatometer" — tracking the remains on older and newer cars. (Modern cars killed more bugs, likely because older models push more air and insects over the vehicle, out of the way.)

"The most surprising thing was how rarely we actually found anything on the plate at all," Paul Tinsley-Marshall of the Kent Wildlife Trust told The Guardian.

So whether it's a lack dead bugs on cars or a lack of living bugs in a forest, a dwindling insect population is bad news for a less-than-resilient ecosystem.

Editor's note: This story has been updated with new information since it was first published in November 2018.

What is the 'windshield phenomenon'?
Popularized in 2017, the windshield phenomenon is used to describe the lack of insects on a windshield after a drive, a sign of a dwindling bug population.