I’m back to work now, after an epic northern adventure that included caribou, arctic hares, moose, flat tires, recurring Pennsylvanians (shout out to my new friends from Reading!), black flies, mosquitoes, and, surprisingly, a remarkably intact Carboniferous swamp. I even got to see the fossils that mark the end of the Cambrian and beginning of the Ordovician and one of the few places where the Earth’s mantle is exposed. I’m still euphoric over these experiences and intend to share some of the entomologia here on our blog. Up first: My experience with the windshield phenomenon.
Our journey resulted in >6,000 km of driving, which equates to about 60 hours behind the wheel. That’s a lot of thinking time. My mind wandered extensively, often dwelling on a graduate seminar I’ve been co-developing on insect declines for spring 2020. You’ve probably read about this disturbing trend in the New York Times, Washington Post, or in any of the myriad research articles published recently on the topic. (This one by Forister et al. (2019) came out while I was gone, and they cite an upcoming review by Wagner (2020) that I am anxious to read.)
Related to this emerging and quite urgent problem is the “windshield phenomenon”, whereby people recall how car windshields used to be coated in the guts and sclerites of pterygotes struck accidentally during their journey. I remember picking whole butterflies, wasps, dragonflies, and hundreds of bibionids and other flies off the grill of my friend’s truck in the early 1980s, including one intact but dead darner that was wrapped around the antenna. (See also Berenbaum 2002.) I do not recall finding similar treasures on my own vehicles in the last 10–20 years. Maybe I stopped looking? Maybe cars have become more aerodynamically streamlined and less prone to insect strikes? Maybe people drive faster now on these roads and the air displacement pushed insects out of the way (see McKenna et al. 2001)? Or maybe it’s a symptom of this large-scale decline in insect diversity and biomass?
The windshield phenomenon has come up many times in conversations with colleagues. “Used to be so bad you’d have to pull over every hour and clean the windshield!” “Seems like it all stopped when <some hypothesis involving insecticides, herbicides, global warming, etc.>” The reality is that we don’t have any hard data about windshield strikes through time, at least that I’m aware of, so on this trip I started paying closer attention to my Subaru’s growing collection of dead insects. Sadly, I didn’t photograph the results until two days before I arrived home, but here’s my anecdotal report … an n of one.
I don’t have any scientifically rigorous conclusions from these casual observations, but I can say that my windshield had to be cleaned repeatedly every day. The photos above do not do it justice. I hit a lot of insects. My bumper and grill had quite a diversity of pterygotes—mostly flies but also at least two dragonflies and a few butterflies. The photos above are probably from two hours of highway driving, post heavy rain storm (which removed the previous layer of insect carcasses almost completely).
I don’t usually find solace in needless carnage, but these casual observations gave me hope that we still have time to do something about biodiversity loss. The insects are still out there. I also wonder if it’s time to study this phenomenon more rigorously. I drove very natural-looking regions of North America. What would my windshield look like driving through the corn belt? What about through Pennsylvania? Also, the diversity of carcasses seems high on my car, but is it really? What if I DNA-barcoded all those dead insects? There could be as many as two billion cars on the road by next year. Maybe there’s an opportunity here for citizen scientists to help us understand the windshield phenomenon and insect declines.