Tag Archives: sampling

It might have been wet, but we had a great time – British Ecological Society Undergraduate Summer School 2019 #BESUG19

 

The beginning of July was a busy time for me, first a week of my Crop Protection Summer School based at Harper Adams University and the following week saw me driving north to Scotland. This time I was heading for the Isle of Great Cumbrae and the Field Studies Council Centre at Millport.

My trusty, rusty car, safely on board the ferry to Millport, leaving grey Largs behind me. I had to drive as I didn’t think I could cope with the Vortis and other collecting equipment on the train 😊

This was the fifth time that I have had the privilege of being allowed to introduce the wonders of entomology to undergraduates aspiring to careers in ecology.  I first joined the BES undergraduate summer school team in 2015 at the inaugural event at Malham Tarn.  On that occasion I did it on my own but since 2016 the entomology team has been greatly strengthened by the very welcome addition of my former student Fran Sconce, now the Outreach Officer at the Royal Entomological Society.

When I arrived in the afternoon it wasn’t raining, although it was rather grey. Fran arrived shortly afterwards and we did the preliminary setting up, getting the lab ready, digging in pitfall traps and deploying the yellow pan traps.  I also gave Fran a quick tutorial in how to use the Vortis as next year, sadly, the Summer School clashes with the International Congress of Entomology which is where I will be instead.

Fran helping with preliminary setting up and learning (after all these years), how to use the Vortis suction sampler.

Yellow pan traps deployed in the hope that the rain forecasted for the night won’t make them overflow 😊

After we had got everything set up, we went for a drive round the island – it didn’t take very long but there was some spectacular scenery on offer, despite the grey skies.

 

View of Bute in the distance.

This must be fantastic when the sun shines.

We then joined the students for our evening meal; after a week of Harper Adams’s excellent catering, I can’t bring myself to call it dinner 😊  It was, however, a great chance to get to know some of the students ahead of our ‘Entomology Day’.  I also took the opportunity to go and listen to Natalia Pilakouta from the University of Glasgow who gave a very entertaining and informative talk about the effects of climate change on sociality.   A whole new concept to me; who would have thought that rising temperatures would affect how individuals interact.  What really made her talk memorable was that she interspersed human examples amounts the sticklebacks and dung beetles 😊 You can also find her on Twitter @NPilakouta

Chris Jeffs (another former student of mine) introducing Natalie Pilakouta for the first plenary of the course.

The bar finally opened at 9 pm where I hastily made my way to get a glass of red wine; after a lifetime of having wine with my evening meal, I was in sore need of this 😊.  It also gave me a chance to meet some more of the students and to get to know them a bit better.   Thence to bed hoping that the weather forecast for Tuesday was wrong.

Unfortunately the Meteorological Office got it right and the view from my bedroom window at 6 am was not quite what I had hoped to see.

The view from my window – Dawn Entomology Day!

Us entomologists are a hardy lot and despite the weather and the slight handicap it put on the use of sweep nets and other sampling devices we headed out to the field, but not before I had subjected the students to my introductory lecture extolling the virtues of insects and their extremely important roles in ecology.

A no-brainer really – if you are a zoologist/ecologist, insects are where it’s at 😊

Once out in the field, despite the rain we had a lovely time pooting, sweeping, beating and using the Vortis, all good fun and as my old games teacher used to say as he ushered us out into the rain to run a cross-country or play rugby, “Character building”.  More seriously though, it was a good introduction to ecological field work and the concept of environmental variability, the sun doesn’t shine all the time.

Sweeping, beating and sucking and perhaps contemplating a swim?

After forty minutes of running about in the rain we headed back to the lab for an hour of sorting and identification for everyone before we started the ‘expert’ session.  We were very pleased that 20% of the students stayed on for the extra hour of getting to grips with insect taxonomy.

Learning how to identify insects in the lab.

After the evening meal, it was time for the now, very traditional, glow in the dark insects and a lecture on moth trapping from Fran.

Using UV torches and fluorescent dust to track carabid beetles.

Fran lecturing on moth trapping and then with the early risers helping her and Chris Jeffs empty and identify the catch; one of which made a bid for freedom, necessitating a bit of ladder work 🙂

Despite the rain we did catch some moths, this Swallowtail for me at least, was the star of the show.

Moths identified it was time for breakfast and getting the car packed; luckily the nets had all dried out overnight and heading for the ferry and the long trip back to Shropshire. It was a great couple of days and I really enjoyed it and am incredibly sad that I will not be able to take part next year. The whole event is a great initiative by the BES, and I am glad that it and the allied summer school for ‘A’ Level students are now a firmly established part of the ecological calendar.   I have only described entomology part of the week, other things were happening; for an excellent account of the whole week I recommend this blog post by one of the students, and not just because she gave me a good report 😊  You can follow her on Twitter too @ecology_student and track down the other comments about the week by using #BESUG19

Although it rained quite hard at times we never had to use this 😊

In terms of hard-core entomology,  this was actually my second collecting insects in the rain experience of the year – you may remember it rained in Bristol!

I am very grateful to the British Ecological Society for inviting me to participate in the first ever Summer School and to keep on inviting me back.  Special thanks to Fran and Chris and also to Christina Ravinet (whom I also taught) from the BES for keeping things running so smoothly.

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…at random

It’s coming up to Christmas so I thought I would be a bit of a Grinch 🙂  As someone who has refereed a lot of papers in my time, one of my particular bugbears is when I come across the phrases,  “taken at random”, “sampled randomly” or variations thereon. My edition of the OED defines at random as “haphazard without aim or purpose, or principle, heedlessly”; the statistical part of the definition qualifies this further as “equal chances for each item to be selected”.  Whenever I see the word random in the methods and materials section I annotate the paper with the phrase “truly random or haphazardly?”  Almost without exception*, when the author responds to my query, it is to admit that in reality they meant haphazardly.

There is a commonly held belief among field biologists that random sampling can be quickly and safely done by standing in a field and throwing a quadrat over their shoulder or closing their eyes and throwing the quadrat into the air. The late great Sir Richard Southwood  deals with this myth in his usual no nonsense style  “Biologists often use methods for random sampling that are less precise than the use of random numbers, such as throwing a stick or quadrat.  Such methods are not strictly random” (Southwood, 1966).  If you have ever tried this yourself, you will, I hope, be the first to admit, that you position yourself in all sorts of non-random ways, to make sure that the quadrat is not going to get lost, get hung-up in a tree, end up in a lake or river or miss the only green bit of vegetation in the field. Other so-called random approaches include the walking around the tree/into the meadow/along the path approach and examining the first leaf/branch/plant you come across after x number of steps and counting what you see on that. Again, this is equally subject to being confounded by the terrain and location of the site, and it is a rare person who isn’t subconsciously swayed for or against a leaf because of its appearance.  I was convinced that this mode of sampling, which is more accurately described as haphazard, was commonly called professorial random sampling.  A recent request by me on Twitter for people to tell me if they had heard of, or used the term themselves, resulted in a zero response rate, so perhaps it was just something we used in our lab. Of course, it wasn’t a random survey so I shouldn’t read too much into it 🙂

So, if you are going to claim that you sampled randomly or selected/arranged randomly, make sure you use a random number generator.  It is very simple to do, although somewhat time-consuming to implement in reality. When I was a student, most good statistics books included among all the other useful tables, a page of random numbers to help you meet a state of true randomness.

Pre-prepared random numbers from my copy of Sokal & Rohlf (1973)

 

Nowadays, you can, if you use Excel, generate random numbers using the function RAND. Those of you who are not fans of Excel can try this handy link https://www.random.org/sequences/

If you’re reading this, you now have no excuses left.  If you are going to claim that you did something randomly make sure you actually did so, or confess that you sampled haphazardly; it is nothing to be ashamed of 🙂 and is much faster than true random sampling, hence its popularity.  Alternatively, you can avoid the whole issue and sample along a stratified transect or arrange your experimental blocks using a Latin Square.

 

References

Sokal, R.R. & Rohlf, F.J. (1973) Introduction to Biostatistsics.  W.H. Freeman & Company, San Francisco.

Southwood, T.R.E. (1966) Ecological Methods.  Chapman & Hall, London.

*I have, on a few occasions, had an author respond that yes, they did indeed use random number tables and/or generators.

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Entomological classics – The D-Vac, Vortis and other motorised suction samplers

I think that all field entomologists of a certain age, certainly those of us over 60, are very familiar with the roar of a hot and smoky two-stroke engine in our ears, coupled with oily hands, aching shoulders and sometimes the smell of burning.  Some younger entomologists may also have had this joyful experience but I suspect they are in a minority among their peers.  The dreaded D-Vac, or to give it its more formal name, The Dietrick Vacuum Sampler was, for a long time, the entomological gold standard in the world of motorised insect sampling.

Part of the UEA cereal aphid research group demonstrating unsafe use of the D-Vac 😊

The D-Vac was the brain wave of an American entomologist Everett Dietrick, who at the time was working on the biological control of the alfalfa aphid, Therioaphis maculata (Dietrick et al., 1959). Their research was hampered by the time they were having to spend estimating the numbers of all the arthropods found in alfalfa fields; they needed a standard sampling method that would allow them to get good estimates of everything rather than using different, and thus time-consuming, methods for each arthropod group.  Essentially, think of a D-Vac as motorised sweep net.  The idea of replacing sweep netting with, in theory at any rate, a non-human biased method* was not new.  Hills (1933) in describing a motorised vacuum pipette for sampling leaf hoppers in beet points out that it is an adaptation of a device put together by a lab assistant in 1926.

The first motorised suction sampler? From Hills (1933) – The modified pipette collector

The first and even clumsier model of the D-Vac (Dietrick et al., 1959), but I suspect more pleasant to use than the back-pack version 🙂

The new improved back-pack version (Dietrick, 1961).  In my experience not very comfortable and on one occasion burst into flames while I was wearing it!

This could, with the aid of a handy pole be used to sample from the top of tall bushes. Not something I have tried so I can’t comment.

While searching for the earliest reference to a motorised suction device that was not a Pooter, I came across one invented a few years earlier than the D-Vac and used by the late, great Southwood of Ecological Methods fame among others, during his PhD (Southwood, 1955; Johnson et al., 1955), which I guess means that it was in operation well before 1955, although the actual full description was not published in a journal until a couple of years later (Johnson et al., 1957).

An earlier suction device used by the late great Southwood during his PhD (1955) (From Johnson et al., 1957).

Ensuring constancy of sample area (From Johnson et al., 1957)

It really does look like the vacuum cleaner we had when I was a kid 🙂

Amusingly, one of the early attempts to replace the D-Vac was actually based on this very vacuum cleaner (Arnold et al., 1973)

I was interested to see that the Johnson apparatus used a barrel to delineate the sample area, something advocated by my colleague Andy Cherrill (Zentane et al., 2016) when using his patent G-Vac, or “Chortis” as we jokingly call it 🙂

A couple of years after I started at Silwood Park and became involved in running the final year field course, a new and revolutionary insect suction sampler appeared on the market – The Vortis™ (Arnold, 1994).  This was lighter than the D-Vac, did not need a bag or net, easier to start, had an ‘idle’ function and mercifully did not have to be carried on your back 🙂

The Vortis™, overall a much pleasanter way to sample insects and generally much easier to start.  Invented in 1993 (Arnold, 1994).

 

Although not cheap, it was less expensive than the D-Vac. This became my suction sampler of choice although we kept our D-vac in good running order so that the students could compare the two samplers.  Surprisingly, few, if any, of the many users of The Vortis™ have done similarly, most just referring to the original description by Arnold (1994), e.g. Mortimer et al., (2002).  This is in marked contrast to the many studies that have compared the D-Vac with sweep-netting, pitfall trapping and swish net sampling (e.g. Johnson et al., 1957; Henderson & Whittaker, 1977; Hand, 1986; Schotzko & O’Keeffe, 1989; Standen, 2000; Brook et al., 2008). There is also a hand-held version of the D-Vac if anyone wants to compare that with the back-pack version.

Jan Dietrick poses with a D-Vac insect Vacuum in Ventura, Calif., on Monday, Oct. 16, 2006. (Photo by Bryce Yukio Adolphson/Brooks Institute of Photography ©2006) http://bryceyukioadolphson.photoshelter.com/image/I0000pmiujJcoGBI

This one looks easier to use than the backpack version but I have never seen it in operation. I am guessing that this was produced in response to the invention of the Vortis™.

Entomologists tend to have limited budgets when it comes to equipment, or anything for that matter, so it is not surprising that they soon came up with the idea of adapting garden leaf blowers into lightweight, inexpensive insect suction samplers (e.g. De Barro, 1991; Stewart & Wright, 1995). These are collectively known as G-Vacs (Zentane et al., 2016) presumably as a reference to their garden origin.

Andy Cherrill test driving his “Chortis” 🙂

 

My colleague Andy Cherrill has compared the catch composition of his own particular G-Vac with that of the Vortis™ and satisfied himself that it is as good as, if not better than the Vortis™ (Cherrill et al., 2017).  Importantly the cost of a G-Vac means that you can get, at least in the UK, six for the same price as a single Vortis™.

I leave you with two fun facts; the two largest motorised insect suction samplers that I have come across are both from the USA (where else?).  The first, mounted on the front of a truck, was used to collect parasites for the biological control of alfalfa aphids.

(1957) http://www.dietrick.org/articles/deke_truckvac.html  Used to collect parasites for mass release against alfalfa aphids.

 

The second, mounted on the front of a tractor was used to control Lygus bugs in strawberry fields in California (Pickel et al., 1994).  The driver/operator in the second example seems to be taking Health & Safety issues a bit more seriously than the team in the first 🙂

Lygus bug control in strawberries, California http://calag.ucanr.edu/Archive/?article=ca.v049n02p19

 

References

Arnold, A.J. (1994) Insect suction sampling without nets, bags or filters. Crop Protection, 13, 73-76.

Arnold, A.J., Needham, P.H. & Stevenson, J.H. (1973) A self-powered portable insect suction sampler and its use to assess the effects of azinphos methyl and endosulfan on blossom beetle populations on oil seed rape. Annals of Applied Biology, 75, 229-233.

Brook, A.J., Woodcock, B.A., Sinka, M. & Vanbergen, A.J. (2008) Experimental verification of suction sampler capture efficiency in grasslands of differing vegetation height and structure. Journal of Applied Ecology, 45, 1357-1363.

Cherrill, A.J., Burkhmar, R., Quenu, H. & Zentane, E. (2017) Suction samplers for grassland invertebrates: the species diversity and composition of spider and Auchenorrhyncha assemblages collected with Vortis (TM) and G-vac devices. Bulletin of Insectology, 70, 283-290.

De Barro, P.J. (1991) A cheap lightweight efficient vacuum sampler.  Journal of the Australian Entomological Society, 30, 207-20.

Dietrick, E.J. (1961) An improved backpack motor fan for suction sampling of insect populations.  Journal of Economic Entomology, 54, 394-395.

Dietrick, E.J., Schlinger, E.I. & van den Bosch, R. (1959) A new method for sampling arthropods using a suction collecting machine and modified Berlese funnel separator.  Journal of Economic Entomology, 52, 1085-1091.

Dietrick. E. J., Schlinger. E. I. & Garber, M. J. (1960). Vacuum cleaner principle applied in sampling insect populations in alfalfa fields by new machine method. California Agriculture January 1960, pp. 9-1 1

Doxon, E.D., Davis, C.A. & Fuhlendorf, S.D. (2011) Comparison of two methods for sampling invertebrates: vacuum and sweep-net sampling. Journal of Field Ornithology, 82, 60-67.

Hand, S.C. (1986) The capture efficiency of the Dietrick vacuum insect net for aphids on grasses and cereals. Annals of Applied Biology, 108, 233-241.

Henderson, 1. F. & Whitaker, T. M. (1977). The efficiency of an insect suction sampler in grassland. Ecological Entomology 2, 57-60.

Hills, O.A. (1933) A new method for collecting samples of insect populationsJournal of Economic Entomology, 26, 906-910.

Johnson, C.G., Southwood, T.R.E. & Entwistle, H.M. (1955) A method for sampling arthropods and molluscs from herbage by suction.  Nature, 176, 559.

Johnson, C.G., Southwood, T.R.E. & Entwistle, H.M. (1957) A new method of extracting arthropods and molluscs from grassland and herbage with a suction apparatus.  Bulletin of Entomological Research, 48, 211-218.

Mortimer, S.R., Booth, R.G., Harris, S.J. & Brown, V.K. (2002) Effects of initial site management on the Coleoptera assemblages colonising newly established chalk grassland on ex-arable land. Biological Conservation, 104, 301-313.

Pickel, C., Zalom, F.G.,  Walsh, D.B. & Welch, N.C. (1994) Efficacy of vacuum machines for Lygus Hesperus (Hemiptera: Miridae) control in coastal California strawberries. Journal of Economic Entomology, 87, 1636-1640.

Schotzko, D.J. & O’Keeffe, L.E. (1989) Comparison of sweep net., D-Vac., and absolute sampling., and diel variation of sweep net sampling estimates in lentils for pea aphid (Homoptera: Aphididae)., Nabids (Hemiptera: Nabidae)., lady beetles (Coleoptera: Coccinellidae)., and lacewings (Neuroptera: Chrysopidae). Journal of Economic Entomology, 82, 491-506.

Southwood, T.R.E. (1955). Some Studies on the Systematics and Ecology of Heteroptera.—Ph.D. thesis, University of London.

Standen, V. (2000) The adequacy of collecting techniques for estimating species richness of grassland invertebrates. Journal of Applied Ecology, 37, 884-893.

Stewart, A.J.A. & Wright, A.F. (1995) A new inexpensive suction apparatus for sampling arthropods in grassland.  Ecological Entomology, 20, 98-102.

Zentane, E., Quenu, H., Graham, R.I. & Cherrill, A.J. (2016) Suction samplers for grassland invertebrates: comparison of numbers caught using Vortis and G-vac devices.  Insect Conservation & Diversity, 9, 470-474.

*

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Pick and mix 13 – Ten more links to things I found of interest

A mixed bag

 

Asian hornets in Spain via Ray Cannon

Unusual dragonfly behaviour via the Bug Blog

Practice what you preach – ecologists shouldn’t fly, I certainly don’t 🙂

Charley Krebs asks how randomly do ecologists sample and does it really matter?

Steffan Lindgren reviews Alexander von Humboldt

This is the link to the paper reporting the huge decline in insect abundance that made all the headlines the other week.  Scary stuff.

This is a link to Manu Saunders’ excellent blog post putting those same headlines in perspective

A great post about why anyone from any background should be able to study and work in science

A poem about how some flowers help bees find them using nanoscale ridges

Using natural history collections as primary data for ecological research

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Being inspired by the BES

This week (20th July) I have had the privilege of being able to interact with 50 undergraduates (mainly just finished their first year) under the auspices of the British Ecological Society’s new undergraduate summer school held at the Field Studies Council’s Malham Tarn Centre. The scheme enables aspiring ecologists to have “an opportunity to enhance their existing knowledge with plenary lectures from senior ecologists, fieldwork, workshops, careers mentoring and more at a week-long residential course” This was especially pleasurable for me because as a school boy and student I spent several enjoyable camping holidays at Malham and it gave me an opportunity to take part in a field course again, something I have missed since leaving Silwood Park where I ran the now defunct annual two-week long Biodiversity & Conservation field course. The programme included two ecological luminaries and old friends of mine, Sue Hartley from the University of York and plant scientist and author, Ken Thompson formerly of Sheffield University and also Clare Trinder from the University of Aberdeen.  Also in the programme was conservation biologist, Stephanie Januchowski-Hartley,  and additional input from the Chartered Institute of Ecology & Environmental Management (CIEEM), microbial ecologist, Dr Rob Griffiths from CEH and ecologist Dr Peter Welsh of the National Trust.

I arrived mid-morning of the Tuesday, having driven up from Shropshire to Yorkshire the night before, having taken the opportunity to stay in the old family home in Kirk Hammerton before it is put up for sale. Whilst there I also set a few pitfall traps to collect some insects that we might not catch otherwise. As it happened they were a dismal failure, returning mainly spiders, harvestmen and woodlice, plus one nice carabid beetle, more of which later. The weather didn’t look all that promising for an insect sampling session but I kept my fingers crossed and hoped that it wouldn’t rain as much as it did almost 40 years ago when my best friend from school and I aborted our camping holiday at nearby Malham Cove after three days of solid rain 😉

Malham Tarn

Malham Tarn – not quite raining

  I was greatly amused on arriving to be greeted by a very large arachnid lurking on an outhouse.

Malham spider

We breed them big in Yorkshire!

Malham Tarn FSC

Malham Tarn Field Studies Centre

After checking my equipment and locating suitable sampling sites I joined the students, Karen Devine, the BES External Affairs manager and some of the PhD mentors for lunch. After lunch it was my slot, a chance to infect (sorry, inspire), fifty ecologically included undergraduates with a love of insects. After being introduced by Karen I launched into my talk to a very full room of students.

Karen Devine

Karen instilling order and attention 😉

Ready to be inspired

Ready and waiting to be inspired

The undergraduates came from thirty different UK universities with a strong female bias, 34:16. Exeter University had four representatives, with Reading, Liverpool John Moores, UCL and Bristol with three each. I was sorry to see that there were no students from my Alma mater Leeds, or from my former institution, Imperial College, once regarded as the Ecological Centre of the UK, although UEA where I did my PhD, had two representatives.  There was also one representative from my current place of work, Harper Adams University. Incidentally one of the students turned out to have gone to the same school that I did in Hong Kong, King George V School, albeit almost fifty years apart; a small world indeed.

I set the scene by highlighting how many insect species there are, especially when compared with vertebrates.

The importance of insects

The importance of insects and plants

Number of animal species

Or to put it another way

After a quick dash through the characteristics of insects and the problems with identifying them, exacerbated by the shortage of entomologists compared with the number of people working on charismatic mega-fauna and primates, I posed the question whether it is a sound policy to base conservation decisions on information gained from such a small proportion of the world’s macro-biota.

Then we were of into the field, although not sunny, at least it was not raining so I was able to demonstrate a variety of sampling techniques; sweep netting with the obligatory head in the bag plus Pooter technique, butterfly netting, tree beating and, as a special treat, motorized suction sampling, in this instance a Vortis.

Sampling

With aid of the PhD mentors and Hazel Leeper from the Linnaen Society, the students were soon cacthing interesting things (not all insects) and using the Pooters like experts.

Students sampling

Getting close up with the insects

I also let some of the students experience the joy of the Vortis, suitably ear-protected of course. All good things come to an end and it was then time to hit the microscopes, wash bottles, mounted pins and insect keys.

In teh lab

Getting stuck in – picture courtesy Amy Leedale

Down the microscope

What’s this?

I was very impressed with how well the students did at getting specimens down to orders and families and have every confidence that there are a number of future entomologists among them. After the evening meal, Kate Harrison and Simon Hoggart from the BES Publications Team introduced the students to the tactics of paper writing and publishing which I think they found something of an eye-opener. The students, after a rapid descent on the bar, enjoyed a Pub Quiz whilst I relaxed with a glass of wine until it was dark enough for me to demonstrate the wonders of using fluorescent dust to track our solitary carabid beetle using my UV torch before heading off to bed.

Fluorescent carabid Eloise Wells

Glow in the dark carabid beetle – the bright lights of Malham Tarn – photo courtesy of Eloise Wells

I was sorry to have to leave the next morning, it would have been great fun to have stayed the full week, but next year I do hope to be able to be there for at least two days and nights so that we can do pitfall trapping and light trapping and of course, have more fun with fluorescent insects.

I hope the students found the whole week inspirational and useful, I was certainly inspired by their obvious enjoyment and interest and will be surprised I if do not come across some of them professionally in the future.

Well done BES and congratulations to Karen and her team for providing such a great opportunity for the students. I am really looking forward to next year and being able to see great Yorkshire features like this in the sunshine 😉

Yorkshire grit

 

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Entomological classics – the pitfall trap

Pitfall arghh I would be amazed if there are any entomologists who have not deployed a pitfall trap or two at some stage in their career. I would also hazard a guess that quite a few non-entomological ecologists have come across the joys of pitfall trap setting and catch sorting as part of their undergraduate training; most field courses seem to include a pitfall trap day, and rightly so.  Pitfall trapping is after all, probably the simplest and most efficient way of collecting data, and not always insects 😉 Pitfall - tapir

Tapir pitfall trap

More seriously though, pitfall traps are a remarkably simple and incredibly versatile way of sampling insects, particularly those that are active on the soil surface (epigeal) e.g carabid beetles. Pitfall forest They can be used in most habitats where you are able to dig into the soil,

Pitfall traps cheap

are very cheap as they can be made from easily obtainable household materials Pitfall traps and can be modified easily depending on your objectives and sampling conditions.  It is very important however, that the lip of the trap is either flush with or below the soil surface.  Not very many beetles or other invertebrates,  are willing to climb up the steep sides  to allow you to capture them. Pitfall - spatial patterns They are also amenable to being deployed in a variety of statistically meaningful ways. (Figure ‘borrowed’ from Woodcock (2005)). Pitfall traps - catch a lot They are of course not perfect.   Some of my students complain that they catch too much!

There has been, and continues to be, much debate about what the catch actually represents.  Are they a measure of activity or of density, i.e. do the trap catches represent the most active and careless beetles, rather than the most abundant?  Southwood (1966) in the first edition of Ecological Methods is fairly dismissive of their use except as a way of studying the activity, seasonal incidence and dispersion of single species and considered them to be of no use whatsoever in comparing communities.  Other authors argue however, that if the trapping is carried out over a long period of time then the data collected can be representative of actual abundance (e.g. Gist & Crossley, 1973; Baars, 1979) and despite Southwood’s comments, they are probably most often used to compare communities (e.g. Rich et al., 2013; Zmihorski et al., 2013;  Wang et al., 2014) For a very thorough account of the use and abuse of pitfall traps see Ben Woodcock’s excellent 2005 article (and I am not just saying that because he is one of my former students). You might expect, given the fact that pitfalls were used by our remote ancestors to trap their vertebrate prey, that entomologists would have adopted this method of trapping very early on, especially given the fact that nature got there first, e.g. as used by larvae of the antlion. Antlion trap

Antlion ‘pitfall traps’.

I was therefore surprised when I started researching this article to find that the earliest reference I could find in the scientific literature was Barber (1931).  I found this very hard to believe so resorted to Twitter.  Richard Jones suggested that a sentence in Pitfall silver sand reference

Notes on Collecting and Preserving Natural History Objects

referring to silver sand pits might be a reference to an early form of pitfall trap.  On further research however, it turned out that sand pits were the results of sand mining operations and were used opportunistically by entomologists.  They worked in a very similar way to Pitfall - St Austell

St Austell Ruddle Moor Sand Pit http://www.cornwall-opc.org/Par_new/a_d/austell_st.php

intercept traps (the subject of a future post).   Interestingly, in some parts of the world, sand pits are now being restored in some places as conservation tools for digger wasp sand bees. Pitfall Bohemia

Sand pit restoration – Bohemia.  http://www.outdoorconservation.eu/project-detail.cfm?projectid=17

  But, I digress.  My next port of call was The Insect Hunter’s Companion (Greene, 1880) which I felt certain would mention pitfall traps.  To my surprise, in the 1880s, entomologists intent on capturing beetles, either pursued them with nets, turned over stones and logs, removed bark from trees, used beating trays or even dug holes in the ground, but never used pitfall traps!  So all very active and energetic methods – no sit and wait in those days 😉 So it seems that Barber’s 1931 description of a pitfall trap does indeed commemorate the first scientific use of a pitfall trap. Barber trap

The Barber trap (Barber, 1931).

Despite their late addition to the entomological armoury and despite the many criticisms levelled at their use, they continue to be perhaps the most widely used method of insect sampling ever; for example if you enter Beetle* AND pitfall* AND trap*  into the Web of Science you will return 1168 hits since 2000, which is more than one a week.  If you further refine your search to exclude beetle but add insect* you can add another 320 hits. If by some chance you have never used a pitfall trap, then I heartily recommend that you set one or two up in a convenient flower bed or even your lawn, and then sit back and wait and see what exciting beasties are roaming your garden.

Post script

Since this post was published I have discovered an earlier reference to the use of pitfall traps (Hertz, 1927).  Many thanks to Jari Niemelä  of Helsinki University for sending me a copy of the reference and many thanks to my eldest daughter for translating the relevant bit, which follows –  “The traps were made of meticulously cleaned tin cans (the rectangle ones used for e.g.  sardines) dug into the ground so deep that the top of the tin was absolutely level with the ground…… it is an ideal way to catch the beetles; with their careless way of running around, they easily fell into the deathtraps, and had no time to use their wings (if they have any)”.  The phrase deathtraps is particularly fine.  The majority of the paper is about the species he caught in different locations and he highlights the fact that he caught seven very rare species using this method.

So this is now the oldest known reference to the use of pitfall traps in the literature, although he does mention that he was using this method to catch beetles in 1914.  But if anyone comes across an earlier reference do let me know.

 

References

Baars, M.A. (1979) Catches in pitfall traps in relation to mean densities of carabid beetles. Oecologia, 41, 25-46.

Barber, H.S. (1931) Traps for cave inhabiting insects.  Journal of the Elisha Mitchell Scientific Society, 46, 259-266.

Gist, C.S. & Crossley, J.D.A. (1973) A method for quantifying pitfall trapsEnvironmental Entomology, 2, 951-952.

Greene, J. (1880) The Insect Hunter’s Companion: Being Instructions for Collecting and Describing Butterflies, Moths, Beetles, Bees, Flies, Etc.  

Hertz, M. (1927) Huomioita petokuoriaisten olinpaikoista.  Luonnon Ystävä, 31, 218-222

Rich, M.C., Gough, L., & Boelman, N.T. (2013) Arctic arthropod assemblages in habitats of differing shrub dominance. Ecography, 36, 994-1003.

Southwood, T.R.E. (1966) Ecological Methods, Chapman & Hall, London.

Wang, X.P., Müller, J., An, L., Ji, L., Liu, Y., Wang, X., & Hao, Z. (2014) Intra-annual variations in abundance and speceis composition of carabid beetles in a temperate forest in Northeast China. Journal of Insect Conservation, 18, 85-98.

Woodcock, B.A. (2005) Pitfall trapping in ecological studies.  Pp 37-57 [In] Insect Sampling in Forest Ecosystems, ed S.R. Leather, Blackwell Publishing, Oxford.

Zmihorski, M., Sienkiewicz, P., & Tryjanowski, P. (2013) Neverending story: a lesson in using sampling efficieny methods with ground beetles. Journal of Insect Conservation, 17, 333-337.

 

Post post script

Pitfall traps are even more versatile than you might think. Mark Telfer has developed a nifty subterranean version http://markgtelfer.co.uk/beetles/techniques-for-studying-beetles/subterranean-pitfall-traps-for-beetles/  and at the opposite end of the spectrum, pitfall traps have also been used in trees to sample spiders (Pinzon & Spence, 2008).

Reference Pinzon, J. & Spence, J. (2008) Performance of two arboreal pitfall trap designs in sampling cursorial spiders from tree trunks.  Journal of Arachnology, 36, 280-286

 

Post post script And for those of you who have had to suffer sitting through the Pokémon movie as I did many years ago, there is also a Pokémon version of the antlion! Pitfall Pokemon

http://bulbapedia.bulbagarden.net/wiki/Trapinch_(Pok%C3%A9mon)

 and don’t forget Winnie the Pooh and his heffalump trap 😉  Hopefully you will use them more carefully than he did. Pitfall trap - Heffalump

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Look Back in Angers – Teaching in France but not in French

I have long been aware of the Erasmus Programme (European Community Action Scheme for the Mobility of University Students) having had many Erasmus students in my classes over the years whilst at Imperial College.  It was however, only after moving to Harper Adams University, that I found out that there was also a similar programme to enable academic staff to spend time teaching at sister institutions.  I was contacted earlier this year by Joséphine Pithon from the Ecole Supérieure d’Agriculture d’Angers who wondered if I would like to come across to Angers a city I am ashamed to admit that I had very little knowledge of.  The chance of spending a week in France, my favourite holiday destination, was too good to turn down and my wife Gill was also very keen to have a short break and refresh her French language skills.  To cut a long story short, on Monday 24th March, we caught the Eurostar to Lille and then the TGV on to Angers, arriving mid-afternoon in, to our dismay, a very wet Angers.  We booked into our hotel, found somewhere not too far away to eat and then retired to deal with emails (sad to say we had both brought our laptops with us) and for me to double-check that my lectures were ready to deliver.
Tuesday dawned warm and sunny, much to Gill’s relief who had a day of sightseeing planned and I walked to ESA, which was only ten minutes away, collecting a roundabout on the way, albeit not as  spectacular as those in the south of France.

Roundabout Angers

 I arrived at a very welcoming ESA and managed to  make myself understood at reception and was introduced to my first class, a group of third years getting their first introduction to

ESA welcome

entomology.  It seemed to go well and despite me lecturing in English they asked a lot of pertinent questions. I then gave them two lectures on sampling and survey methods before going for lunch with my hosts.  I must give the staff canteen (cantine) a rave review – for less than €5 we got a three course lunch with coffee. Then it was back to lecture to a fourth year group about biological control and pest management, again to a very interactive group of students.  Then it was the short walk back to the hotel followed by an excellent meal in the city centre with my new French colleagues.  On the way we admired the bendy trams and marveled at the ingenuity of having ‘green’ tramways wherever possible.

 Tram  Tram lines

The next day I gave a seminar and then we headed out into the field with the third year students to collect insects and other invertebrates using a mixture of methods, pitfall traps, yellow pan traps, pooters, beating trays (known as Japanese umbrellas in French), sweep nets and extendable butterfly nets.  French students in the field are very similar in

Students getting briefed            Pan trap                Angers fieldwork

Extended net             Head first               Using  the pooter

behaviour to their British counterparts 😉  Then it was the end of the day and time to relax and find somewhere nearby to eat and get ready for a morning in the laboratory on Thursday.

Thursday morning was spent with the students helping them identify the various organisms that they had brought back from our day in the field.  It appears that whilst students have to wear lab coats staff are exempt!  Our lab manager at Harper Adams would never allow that; I am frequently being told off for popping into the lab sans coat.

Busy in the lab

In the lab I had to use my French a bit more as some students were better than others at English and in a one to one situation I feel a little less hesitant about demonstrating my inept language skills.  I think we all had a fun morning and learnt a lot from each other.  After an excellent lunch it was time for a break; there is no teaching at ESA on a Thursday afternoon so I was free to join Gill for an afternoon of sightseeing around Angers.  Needless to say it began to rain!  Nevertheless we saw the magnificent Château d’Angers, once the home of René I a most impressive building even in the rain and with a nice entomological surprise on the ramparts; beehives..

Chateau 2           Chateau                Bee hives

And of course a mini-vineyard complete with a rose bush at the end of the row to give early warning of mildew infections! Great to see pest management in action;-)

Vine yard  Rose at end of row

Thursday evening saw us at a great little restaurant in the city centre where we met up with Professor David Logan a plant physiologist at the University of Angers, and someone I had previously only met on Twitter.  He introduced us to a couple of very nice local wines and we had a superb (and very reasonably priced) meal. It was a great end to a fantastic and educational trip.  I think it is very impressive that the French students are willing and able to be lectured to in English.  I am ashamed to say that I think that very few of our own students would be able to cope with a week of teaching in French!

Given the chance I would definitely like to repeat the experience and spend more time there.

Post script
Whilst roaming the corridors of ESA I came across a departmental notice board where I saw this cutting from the February issue of the L’Éleveur laitier a French agricultural magazine, and was very amused to see how they portrayed British farmers!

How they see us

 

 

 

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