Tag Archives: splatometer

Planes, trains and automobiles – insect killers?

I couldn’t not use this – it is (sadly) one of my favourite films 😊

Anyone who has driven (or walked) along a road will have come across roadkill, be it squirrels, pheasants, badgers, deer or even something more exotic, perhaps it us only us entomologists who notice the squashed invertebrates ☹

Dead carabids and mayflies Shay Lane, Staffordshire, 8th June 2021

But, lets leave the roadkill for a moment, and in the spirit of the title of the film, start in the air. The first thing I discovered when I started to search for the effects of aircraft on insects is the paucity of literature on the subject – it turns out that people are much more interested in stopping disease carrying insects being transported by air or, and coming as a bit of a surprise to me, stopping insects causing plane crashes (House et al., 2020; Grout & Russell, 2021). The aircraft industry is so concerned about the physical dangers posed to ‘planes by insects that NASA actually have a Bug Team dedicated to developing insect proof aircraft.

I am, however, more concerned about how dangerous aircraft are to insects. First, we need to know how many insects are up there and what the probability of them being struck and killed by aircraft is. I’m guessing that bug strike is pretty common, otherwise NASA wouldn’t have a Bug Team. The majority of insects in the air are found at 300-600 m, although this does vary in relation to time of day (Reynolds et al., 2005). Getting a figure for the actual number of insects in the air is as you might expect, actually quite difficult.  The first attempt to trap and collect insects using an aircraft was in 1926 in Louisiana (USA) using a specially designed trap (Glick, 1939).  These do not seem to have been particularly effective as 5 years of trapping, involving 1528 hours of flying, caught just under 30 000 insects (Glick, 1939).  Those of us who have operated pitfall traps for any length of time would consider this a very modest haul 😊

Glick (1939) The aircraft insect trap

That said, the exercise was obviously more hazardous than even collecting insects from roundabouts as this very laconic extract highlights:

 “The skill of the pilots who flew the collecting airplanes is evidenced by the fact that no fatalities occurred.  Only one major accident occurred, when a forced landing resulted in the destruction of the craft and injury to both the pilot (McGinley) and the writer. Such mishaps must be expected in a more or less hazardous undertaking.”

The distribution of catch number was very similar to that reported from the more recent UK study using radar (Reynolds et al., 2005) and is reinforced by this statement from the NASA Bug Team; “The reason we do these tests at low altitudes or do a lot of takeoffs and landings is because bug accumulation occurs at anywhere from the ground to less than 1,000 feet,” said Mia Siochi, a materials researcher at NASA Langley”.

Given the number of flights made globally and the investment being made into protecting aircraft from bug strike, I would assume that the number of insects being killed by aircraft worldwide is probably very high. I am sure that someone with the skill, time and inclination, can probably come up with a fairly realistic figure.  Over to you Dear Readers.

Next up, if we keep to the film title, are trains.  There has been a bit more work looking at the damage that trains do to insects, not a lot, but something is better than nothing.  Work collecting train kill from railway lines showed that snails were particularly vulnerable to being run over, similar to the effects on trail-following ermine moth caterpillars that I observed in Finland in 1981, with Ephemeroptera (Mayflies) in second place (Pop et al., 2020). This, as the authors suggest, was almost certainly due to the time of year and the presence of a lake nearby. Unfortunately no one has done the equivalent of a train splatometer which might be rewarding as these observations from correspondence in British Birds magazine suggest that locomotive engines are causing some mortality to flying insects.  Over to you Bug Life. How about getting the train companies to fit splatometers?

Finally, cars and their effect on insect life. There is anecdotal evidence out there, after all as drivers we have all seen moths in our headlights at night and used our windscreen washers and wipers to try and remove dried on insect corpses and their haemolymph from our front windscreens.

An observation by Ian Bedford

My front bumper – sadly (or perhaps not) much less insect spattered than in the past

Yes, anecdotally we know that insects are being hit by cars (see above) and on my front number plate, a couple of weeks ago (beginning of June) I counted 73 insects, mainly aphids after a 245 km trip. The problem as I see it, is quantifying the numbers killed and calculating the effect that this has on insect abundance. I have mentioned the splatometer in an earlier post which attempts to standardise the number plate counts and I am pleased to see that this has now been revived by Bug Life, and will hopefully carry on for many years. The idea behind this is that over the years we will be able to see if insect numbers as reflected by the change in numbers of splats are increasing, decreasing of remaining the same.  This will not, certainly as described, tell us how many insects are being killed by road using vehicles, although it would be possible if the data were collected over delineated stretches of road (Baxter-Gilbert et al., 2015).  It is not just flying insects that are killed by cars; not all flying insects fly across roads, many seem happy to walk to the other side, reckless as that may seem.

A brave, or possibly fool-hardy carabid beetle crossing the road – Guild Lane, Sutton, Staffordshire, 9th June 2021.

There have been enough studies done looking at the interactions between roads and insects for a review article to have been published fairly recently, although not all the papers deal directly with mortality effects (Munõz et al., 2015). Many studies have recorded the species affected and the number of dead individuals found but few have attempted to calculate what this means in total. Most studies, as we might expect, have been on large, easily identifiable charismatic species (Munõz et al., 2015) and it from these that we do have some idea of the magnitude of the mayhem caused by road traffic. Some of the figures are incredibly high. A survey of Odonata road kill, albeit near a wetland, of two 500 m stretches of dual carriageway in the Great Lakes region of the USA revealed that at least 88/km/day were being hit and killed by vehicles (Riffell, 1969).  Another study in the USA, this time on Lepidoptera, calculated that about 20 000 000 butterflies (mainly Pieridae) were killed in one week in September (McKenna et al., 2001). The most dramatic figures however, are those from a study in Canada which estimated that 187 billion pollinators (mainly Hymenoptera) are killed over the summer in North America (Baxter-Gilbert et al., 2015).  An unpublished study by Roger Morris (thank you Richard Wilson @ecology_digest for bringing this to my attention) also highlights the dangerous effects of cars on Hymenoptera). Despite the mounting evidence of the harm that road traffic does to insects there is remarkably little information about how this can be reduced, although I did find a paper that noted that if insects are struck by cars driving at speeds of 30-40 km/h they survive the crash whereas speeds greater than this prove fatal (Rao & Girish, 2007).  It might be possible to impose insect safe speed limits along stretches of road that go through sites of special insect interest (perhaps I should try and coin that acronym, SSII, as an additional/alternative term to SSSI (Sites of Special Scientific Interest), but I am not sure how amenable drivers would be to signs telling them to slow down because of insects😊, considering how few drivers slow down in response to the signs warning them about deer and other vertebrate hazards. Another option would be to design road vehicles so that the air flow across them pushes insects away rather than into them; this may already be fortuitously happening as Manu Saunders points in her interesting post about the ‘windscreen anecdote’.  That said, even if cars are more aerodynamic and less likely to splatter insects, the levels of road kill reported in the papers I have cited earlier, still imply that insects are being killed by traffic in huge numbers.

This one didn’t get stuck on a car, but died just the same – A519 outside Forton, Staffordshire, 15th June 2021

Even if we do accept that deaths down to direct impact with vehicles is lower than in the past, the roads on which we drive our cars are also having a negative effect on insect numbers. Roads, particularly those surfaced with tarmacadam, present an inhospitable surface to some insects which may make them reluctant to fly or walk across. It has been shown that bee and was communities can be different on different sides of a road (Andersson et al., 2017) as the road act as barriers, particularly for smaller species of bees (Fitch & Vaidya, 2021).

Despite the mortality that vehicles impose on insects, roads are not necessarily a totally bad thing for invertebrates; road verges, when sympathetically managed, can provide overwintering sites for a range of arthropod species (Saarinen et al., 2005; Schaffers et al., 2012) and some insect species seem to enjoy feeding on roadside vegetation because of the increased nitrogen content of the plants living alongside traffic (Jones & Leather, 2012).

Overall however, given the very high mortality rates directly associated with cars and other road traffic and the very real indirect effects caused by habitat fragmentation, it would seem that we have much to do to make roads safer for insects and other animals.

References

Andersson, P., Koffman, A., Sjödin, N.E. & Johansson, V. (2017) Roads may act as barriers to flying insects: species composition if bees and wasps differs on two sides of a large highway.  Nature Conservation, 18, 41-59.

Baxter-Gilbert, J.H., Riley, J.L., Neufeld, C.J.H., Litzgus, J.D., & Lesbarreres, D. (2015) Road mortality potentially responsible for billions of pollinating insect deaths annually. Journal of Insect Conservation, 19, 1029-1035.

Fitch, G. & Vaidya, C. (2021) Roads pose a significant barrier to bee movement, mediated by road size, traffic and bee identity. Journal of Applied Ecology, 58,1177–1186.

Glick, P.A. (1939) The Distribution of Insects, Spiders, and Mites in the air.  Technical Bulletin no. 673, USDA. https://naldc.nal.usda.gov/download/CAT86200667/PDF

Grout, A. & Russell, R.C. (2021)H Aircraft disinsection: what is the usefulness as a public health measure? Journal of Travel Medicine, 28, taaa124.

House, A.P.N., Ring, J.G., Hill, M.J. & Shaw, P.P. (2020) Insects and aviation safety: The case of the keyhole wasp Pachodynerus nasidens (Hymenoptera: Vespidae) in Australia. Transportation Research Interdisciplinary Perspectives, 4, 100096.

Jones, E.L. & Leather, S.R. (2012) Invertebrates in urban areas: a review. European Journal of Entomology, 109, 463-478.

McKenna, D.D., McKenna, K., Malcolm, S.B. & Berenbaum, M.R. (2001) Mortality of lepidoptera along roadways in Central Illinois. Journal of the Lepidopterist’s Society, 55, 63-68.

Melis, C., Olsen, C.B., Hyllvang, M., Gobbi, M., Stokke, B.G., & Røskaft, E. (2010) The effect of traffic intensity on ground beetle (Coleoptera: Carabidae) assemblages in central Sweden. Journal of Insect Conservation, 14, 159-168.

Munõz, P.T., Torres, F.P. & Megias, A.G. (2015) Effect of roads on insects: a review. Biodiversity & Conservation, 24, 659-682.

Pop, D.R., Maier, A.R.M., Cadar, A.M., Cicort-Lucaciu, A.S., Ferenți, S. & Cupșa, D. (2020) Slower than the trains! Railway mortality impacts especially snails on a railway in the Apuseni Mountains, Romania. Annales Zoologici Fennici, 57, 225-235.

Rao, R.S.P & Girish, M.K.S. (2007) Road kills: assessing insect casualties using flagship taxon. Current Science, 92, 830-837.

Reynolds, D.R., Chapman, J.W., Edwards, A.S., Smith, A.D., Wood, C. R., Barlow, J. F. and Woiwod, I.P. (2005) Radar studies of the vertical distribution of insects migrating over southern Britain: the influence of temperature inversions on nocturnal layer concentrations. Bulletin of Entomological Research, 95, 259-274.

Riffell, S.K. (1999) Road mortality of dragonflies (Odonata) in a Great Lakes coastal wetland. Great Lakes Entomologist, 32, 63-74.

Saarinen, K., Valtonen, A., Jantunen, J. & Saarnio, J. (2005) Butterflies and diurnal moths along road verges: does road type affect diversity and abundance? Biological Conservation, 123, 403-412.

Schaffers, A.P., Raemakers, I.P., & Sýkora, K.V. (2012) Successful overwintering of arthropods in roadside verges. Journal of Insect Conservation, 16, 511-522.

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Pick & Mix 62 – bees, orchards, bugs, pollinators, blowflies, birds, beetles and spuds

Another great piece of natural history writing from Philip Strange – Sunday in the orchard with butterflies

Carrion flowers and their pollinators – Don’t stop and smell the flowers

One of the biggest challenges facing emerging pollinators each spring is finding food. What we plant in our gardens, parks and around our workplaces can be a huge help for foraging insects. So take a bow Dance Connect in Kinross who have skilfully transformed the area around their dance and fitness studio into a pollinator-friendly hot spot.

Great review of bee emojis – very amusing

Is your local council verge friendly?  Very interesting and useful article revealing which councils are taking biodiversity issues seriously 

Nice article from one of my former MSc students about the usefulness of blowflies and also has a nice graphic showing the pollinator league of fame

Six reasons why potatoes are good for you – I have always been a great fan of the not so humble spud as my carbohydrate source – so much more tasty and versatile than rice

Is our kindness to garden birds harming other bird species?  Garden bird feeders are boosting blue tit numbers – but leaving other species hungry

Bug splatter – please take part

What’s that beetle? Ask the algorithm.  Machine learning and beetle identification 

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Insects in flight – whatever happened to the splatometer?

I have been musing about extinctions and shifting baselines for a while now; BREXIT and an article by Simon Barnes in the Sunday Times magazine (3rd September 2016) finally prompted me to actually put fingers to keyboard.  I fear that BREXIT will result in even more environmental damage than our successive governments have caused already.  They have done a pretty good job of ignoring environmental issues and scientific advice (badgers) even when ‘hindered’ by what they have considered restrictive European legislation and now that we head into BREXIT with a government not renowned for its care for the environment I become increasing fearful for the environment. Remember who it was who restructured English Nature into the now fairly toothless Natural England, because they didn’t like the advice they were being given and whose government was it who, rather than keep beaches up to Blue Flag standard decided to reclassify long-established resort beaches as not officially designated swimming beaches?  And, just to add this list of atrocities against the environment, we now see our precious ‘green belt’ being attacked.

My generation is liable to wax lyrical about the clouds of butterflies that surrounded us as we played very non PC cowboys and Indians outside with our friends in the glorious sunshine.  We can also fondly reminisce about the hordes of moths that used to commit suicide in the lamp fittings or beat fruitlessly against the sitting room windows at night.  The emptying of the lamp bowl was a weekly ceremony in our house.  We also remember, less fondly, having to earn our pocket-money by cleaning our father’s cars, laboriously scraping the smeared bodies of small flies from windscreens, headlamps and radiator grilles on a Saturday morning.  A few years later as students, those of us lucky enough to own a car, remember the hard to wash away red smears left by the eyes of countless Bibionid (St Mark’s) flies, as they crashed into our windscreens.

splat-1

Typical Bibionid – note the red eyes; designed specially to make a mess on your windscreen 🙂 https://picasaweb.google.com/lh/photo/GBgoGHhRbj-eUUF9SxZ4s9MTjNZETYmyPJy0liipFm0?feat=embedwebsite

Are these memories real or are we looking back at the past through those rose-tinted glasses that only show the sunny days when we lounged on grassy banks listening to In the Summertime and blank out the days we were confined to the sitting room table playing board games?

We have reliable and robust long-term data sets showing the declines of butterflies and moths over the last half-century or so (Thomas, 2005; Fox, 2013) and stories about this worrying trend attract a lot of media attention. On a less scientific note, I certainly do not find myself sweeping up piles of dead moths from around bedside lamps or extricating them from the many spider webs that decorate our house.  Other charismatic groups, such as the dragonflies and damselflies are also in decline (Clausnitzer et al., 2009) as are the ubiquitous, and equally charismatic ground beetles (carabids) (Brooks et al., 2012).  But what about other insects, are they too on the way out?  A remarkable 42-year data set looking at the invertebrates found in cereal fields in southern England (Ewald et al., 2015) found that of the 26 invertebrate taxa studied less than half showed a decrease in abundance; e.g. spiders, Braconid parasitic wasps, carabid beetles, Tachyporus beetles, Enicmus (scavenger beetles), Cryptophagid fungus beetles, leaf mining flies (Agromyzids), Drosophila, Lonchopteridae (pointed wing flies), and surprisingly, or perhaps not, aphids.  The others showed no consistent patterns although bugs, excluding aphids, increased over the study period.  Cereal fields are of course not a natural habitat and are intensely managed, with various pesticides being applied, so are perhaps not likely to be the most biodiverse or representative habitats to be found in the UK.

But what about the car-smearing insects, the flies, aphids and other flying insects?  Have they declined as dramatically?  My first thought was that I certainly don’t ‘collect’ as many insects on my car as I used to, but is there any concrete evidence to support the idea of a decline in their abundance.  After all, there has been a big change in the shape of cars since the 1970s.

splat-2

Top row – cars from 1970, including the classic Morris 1000 Traveller that my Dad owned and I had to wash on Saturdays.

Bottom row the cars of today, sleek rounded and all looking the same.

 

Cars were  much more angular then, than they are now, so perhaps the aerodynamics of today’s cars filter the insects away from the windscreen to safety? But how do you test that?  Then I remembered that the RSPB had once run a survey to address this very point.  Sure enough I found it on the internet, the Big Bug Count 2004, organised by the RSPB.  I was very surprised to find that it happened more than a decade ago, I hadn’t thought it was that long ago, but that is what age does to you 🙂

splat-3

The “Splatometer” as designed by the RSPB

The idea, which was quite cool, was to get standardised counts of insect impacts on car number platesThe results were thought to be very low as the quote below shows, but on what evidence was this based?

“Using a cardboard counting-grid dubbed the “splatometer”, they recorded 324,814 “splats”, an average of only one squashed insect every five miles. In the summers of 30-odd years ago, car bonnets and windscreens would quickly become encrusted with tiny bodies.”  “Many people were astonished by how few insects they splatted,” the survey’s co-ordinator Richard Bashford, said.

Unfortunately despite the wide reporting in the press at the time, the RSPB did not repeat the exercise.  A great shame, as their Big Garden Birdwatch is very successful and gathers useful data.   So what scientific evidence do we have for a decline in these less charismatic insects?  Almost a hundred years ago, Bibionid flies were regarded as a major pest (Morris, 1921) and forty years ago it was possible to catch almost 70 000 adults in a four week period from one field in southern England (Darcy-Burt & Blackshaw, 1987).   Both these observations suggest that in the past Bibionids were very common.  It is still possible to pluck adult Bibionids out of the air (they are very slow, clumsy fliers) in Spring, but if asked I would definitely say that they are not as common as they were when I was a student.  But as Deming once said, “Without data, you’re just another person with an opinion.”  In the UK we are fortunate that a long-term source of insect data exists, courtesy of Rothamsted Research, the longest running agricultural research station in the world.  Data have been collected from a nationwide network of suction and light traps for more than 50 years (Storkey et al., 2016).   Most of the publications arising from the survey have tended to focus on aphids (Bell et al., 2015) and moths (Conrad et al., 2004), although the traps, do of course, catch many other types of insect (Knowler et al., 2016).  Fortuitously, since I was interested in the Bibionids I came across a paper that dealt with them, and other insects likely to make an impact on cars and splatometers (Shortall et al., 2009).  The only downside of their paper was that they only looked at data from four of the Rothamsted Suction Traps, all from the southern part of the UK, which was a little disappointing.

splat-4

Location and results of the suction traps analysed by Shortall et al. (2009).

Only three of the trap showed downward trends in insect biomass over the 30 years (1973-2002) analysed of which only the Hereford trap showed a significant decline.  So we are really none the wiser; the two studies that focus on a wider range of insect groups (Shortall et al., 2009; Ewald et al., 2015) do not give us a clear indication of insect decline.   On the other hand, both studies are limited in their geographic coverage; we do not know how representative the results are of the whole country.

What a shame the RSPB stopped collecting ‘splatometer’ data, we would now have a half-decent time series on which to back-up or contradict our memories of those buzzing summers of the past.

Post script

After posting this I came across this paper based on Canadian research which shows that many pollinators, possibly billions are killed by vehicles every year.  This reduction in insect numbers and biomass has also been reported in Germany.

References

Bell, J.R., Alderson, L., Izera, D., Kruger, T., Parker, S., Pickup, J., Shortall, C.R., Taylor, M.S., Verrier, P. & Harrington, R. (2015) Long-term phenological trends, species accumulation rates, aphid traits and climate: five decades of change in migrating aphids.  Journal of Animal Ecology, 84, 21-34.

Brooks, D.R., Bater, J.E., Clark, S.J., Montoth, D.J., Andrews, C., Corbett, S.J., Beaumont, D.A., & Chapman, J.W. (2012) Large carabid beetle declines in a United Kingdom monitoring network increases evidence for a widespread loss of insect biodiversity. Journal of Applied Ecology, 49, 1009-1019.

Clausnitzer, V., Kalkman, V.J., Ram, M., Collen, B., Baillie, J.E.M., Bedjanic, M., Darwall, W.R.T., Dijkstra, K.D.B., Dow, R., Hawking, J., Karube, H., Malikova, E., Paulson, D., Schutte, K., Suhling, F., Villaneuva, R.J., von Ellenrieder, N. & Wilson, K. (2009)  Odonata enter the biodiversity crisis debate: the first global assessment of an insect group.  Biological Conservation, 142, 1864-1869.

Conrad, K.F., Woiwod, I.P., Parsons, M., Fox, R. & Warren, M.S. (2004) Long-term population trends in widespread British moths.  Journal of Insect Conservation, 8, 119-136.

Darcy-Burt, S. & Blackshaw, R.P. (1987) Effects of trap design on catches of grassland Bibionidae (Diptera: Nematocera).  Bulletin of Entomological Research, 77, 309-315.

Ewald, J., Wheatley, C.J., Aebsicher, N.J., Moreby, S.J., Duffield, S.J., Crick, H.Q.P., & Morecroft, M.B. (2015) Influences of extreme weather, climate and pesticide use on invertebrates in cereal fields over 42 years. Global Change Biology, 21, 3931-3950.

Fox, R. (2013) The decline of moths in Great Britain: a review of possible causes. Insect Conservation & Diversity, 6, 5-19.

Knowler, J.T., Flint, P.W.H., & Flint, S. (2016) Trichoptera (Caddisflies) caught by the Rothamsted Light Trap at Rowardennan, Loch Lomondside throughout 2009. The Glasgow Naturalist, 26, 35-42.

Morris, H.M. (1921)  The larval and pupal stages of the Bibionidae.  Bulletin of Entomological Research, 12, 221-232.

Shortall, C.R., Moore, A., Smith, E., Hall, M.J. Woiwod, I.P. & Harrington, R. (2009)  Long-term changes in the abundance of flying insects.  Insect Conservation & Diversity, 2, 251-260.

Storkey, J., MacDonald, A.J., Bell, J.R., Clark, I.M., Gregory, A.S., Hawkins, N. J., Hirsch, P.R., Todman, L.C. & Whitmore, A.P. (2016)  Chapter One – the unique contribution of Rothamsted to ecological research at large temporal scales Advances in Ecological Research, 55, 3-42.

Thomas, J.A. (2005) Monitoring change in the abundance and distribution of insects using butterflies and other indicator groups.  Philosophical Transactions of the Royal Society B, 360, 339-357

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