Why Do Insects Avoid My Windscreen Now?

I call it soap star syndrome. Take a character away from the cobbles of Wetherfield or the squares of Walford and usually some dreadful disaster befalls them. There was a time when I wondered whether I too was a victim. Leaving the sanctuary of suburbia to savour the delights that the countryside has to offer on a summer’s night in my car, I soon found I had turned into a mass killer. So delighted were the hordes of flies, gnats, moths and other assorted bugs at the advent of my headlights that they would fling themselves selflessly at the windscreen in a kind of invertebrate suttee.

And what a mess they made. The screen soon became a mass of blotches and smears, made worse by the injudicious use of windscreen wipers. Instead of clearing the smudges, they simply spread them more evenly over the surface of the glass. Often the only way to see where I was going was to stop the car, unfurl a dampened chamois leather and manually clear the screen, before setting off again. Occasionally, I had to repeat the exercise several times before I reached my destination.

That was then, but these days I cannot honestly remember the last time that my windscreen took on the appearance of an insect charnel house. Perhaps it has something to do with the design and shape of my car. The shape of later models I have bought has been more aerodynamic, or, at least, that was what the gushing sales representative always told me, than the angular shapes of the older cars. Did this mean that the insects attracted to the glare of my headlights were confronted with a lower obstacle to negotiate to escape the oncoming windscreen?

Or was there some Darwinian evolutionary thing going on? We are told that the survival of species is dependent upon weeding out those characteristics which are likely to lessen the creature’s chances of survival and encouraging those traits which are likely to put it on top of its specific pile. Clearly, having a propensity to throw yourself at the nearest on-coming windscreen is not a characteristic that is conducive to ensuring the long-term future of your species. Have those insects which have survived or avoided their motoring Armageddon developed a breed that can eschew the momentary attraction of a glaring headlight?

On the other hand, could it be something to do with the increased density of traffic, even in our country lanes? With a greater number of windscreens to crush themselves on, the carnage is spread around. The same number of insects may be killed but the individual motorist sees a reduction on their individual windscreen.

Or is it simply that there are fewer insects as a result of climate change, alterations in land use, enhanced deployment of insecticides and the like, notwithstanding the considerable conservation effort directed at improving the lot of invertebrates?

Fortunately, there are people with greater brains and more time on their hands to give the decline in the number of insect-splattered windscreens, the windscreen phenomenon as it is known in scientific circles, some serious consideration. One of the earliest pieces of research was carried out in Denmark. Each summer from 1997 to 2017, the researchers made sixty-five car journeys along the same road at the same speed and collected data about the number of dead insects on their windscreens. Over the twenty-year period they noted a decrease of around 80%, a phenomenal reduction.

Here in Britain, in 2004 the Royal Society for the Protection of Birds (RSPB), recognising the environmental link between insects and birds, prey and predator, encouraged motorists to attach a PVC film to their freshly-cleaned car number plate, what they called a splat-o-meter, and count the number of insects they squashed during a journey. The experiment recorded 324,814 splats, which boiled down to a splat every five miles travelled. 

The survey was not repeated, the results rather hung in the air. For the purists there were a couple of serious deficiencies in the way that the survey was set up, no attempt being made to differentiate between the results from short and long journeys nor between the ages of the vehicles involved. In 2019 Paul Tinsley-Marshall and his team from Kent Wildlife Trust decided to address these shortcomings, whilst repeating the RSPB splat test, and to compare results fifteen years on.

The same methodology was used, a splat-o-meter attached to a number plate, but participants were asked to differentiate their results between journeys within the boundaries of Kent and those which crossed county lines. Classic car owners were actively recruited, ensuring that there were cars ranging in age from 1957 to 2018. The results revealed that there was a statistically significant reduction in splat density between the two surveys of the order of 50%, the Kent survey recording a splat every ten miles. Interestingly, they discovered that newer vehicles had a positive effect on splat density, meaning that more invertebrates were squashed by newer cars than older ones.

Fascinating as these results are, it is always satisfying to see rigorous research confirm one’s empirical findings, it doesn’t get us very far with the most important question, the why. There is more work to be done, as Kent Wildlife Trust admit, building up a trend over time to confirm whether there is really a decline or whether other factors such as the weather have had an effect, to increase confidence in the findings over the variations in vehicle ages and to extend the geographic reach of the survey. Even this, though, doesn’t get to the nub of the problem, whether the insect population really has declined to the extent that the data suggest.

In a strange kind of way, I miss having to clear my windscreen of dead insects and I hope it isn’t a harbinger of a bigger problem.

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