Tag Archives: Coleoptera

Twisted, hairy, scaly, gnawed and pure – side-tracked by Orders

I’m supposed to be writing a book, well actually two, but you have to be in the right mood to make real progress. Right now, I’m avoiding working on one of the three chapters that I haven’t even started yet* and I really should be on top of them by now as I have already spent the advance, and have less than a year to go to deliver the manuscript 😦 Instead of starting a new chapter I’m tweaking Chapter 1, which includes an overview of Insect Orders.  While doing that I was side tracked by etymology. After all, the word is quite similar to my favourite subject and a lot of people confuse the two. Anyway, after some fun time with my Dictionary of Entomology, (which is much more of an encyclopaedia than a dictionary), and of course Google, I have great pleasure in presenting my one stop shop for those of you who wonder how insect orders got their names.  Here they are, all in one easy to access place with a few fun-filled facts to leaven the mixture.

Wings, beautiful wings (very much not to scale)

First, a little bit of entomological jargon for those not totally au fait with it.  Broadly speaking we are talking bastardised Greek and Latin. I hated Latin at school but once I really got into entomology I realised just how useful it is.  I didn’t do Greek though 😊, which is a shame as Pteron is Greek for wing and this is the root of the Latin ptera, which features all over the place in entomology.

Since I am really only talking about insects and wings, I won’t mention things like the Diplura, Thysanura and other Apterygota.  They don’t have wings, the clue being in the name, which is derived from Greek; A = not, pterygota, derived from the Greek ptérugos = winged, which put together gives us unwinged or wingless. In Entojargon, when we talk about wingless insects we use the term apterous, or if working with aphids, aptera (singular) or apterae (plural).   I’m going to deal with winged insects, the Exopterygota and the Endopterygota. The Exopterygota are insects whose wings develop outside the body and there is a gradual change from immature to adult.  Think of an aphid for example (and why not?); when the nymph (more Entojargon for immature hemimetabolus insects) reaches the third of fourth instar (Entojargon for different moulted stages), they look like they have shoulder pads; these are the wing buds, and the process of going from egg to adult in this way is called incomplete metamorphosis.

Fourth instar alatiform nymph of the Delphiniobium junackianum the Monkshood aphid.  Picture from the fantastic Influential Points site https://influentialpoints.com/Images/Delphiniobium_junackianum_fourth_instar_alate_img_6833ew.jpg (Any excuse for an aphid pciture)

In the Endopterygota, those insects where the wings develop inside the body, e.g butterflies and moths, the adult bears no resemblance to the larva and the process is described as complete metamorphosis and the life cycle type as holometabolous. It is also important to note that the p in A-, Ecto- and Endopterygota is silent.

Now on to the Orders and their names.  A handy tip is to remember is that aptera means no wings and ptera means with wings.  This can be a bit confusing as most of the Orders all look and sound as if they have wings.  This is in part, due to our appalling pronunciation of words; we tend to make the syllables fit our normal speech patterns which doesn’t necessarily mean breaking the words up in their correct component parts. Diptera and Coleoptera are two good examples – we pronounce the former as Dip-tera and informally as Dips.  From a purist’s point of view, we should be pronouncing the word Di-tera – two wings, and similarly, Coleoptera as Coleo-tera, without the p 🙂 Anyway, enough of the grammar lessons and on with the insects.

Exopterygota

Ephemeroptera The Mayflies, lasting a day or winged for a day J The oldest extant group with wings. They are also a bit weird, as unlike other Exopterygota they have a winged sub-adult stage

Odonata              Dragonflies and Damselflies – think dentists, toothed, derived from the Greek for tooth, odoús. Despite their amazing flight capability, the name refers to their toothed mandibles.  The wings do get a mention when we get down to infraorders, the dragonflies, Anisoptera meaning uneven in that the fore and hind wings are a different shape and the damselflies, Zygoptera  meaning even or yoke, both sets of wings being pretty much identical.

Dermaptera       Earwigs, leathery/skin/hide, referring to the fore-wings which as well as being leathery are reduced in size.  Despite this, the much larger membranous hind wings are safely folded away underneath them.

A not very well drawn (by me) earwig wing 😊

Plecoptera          Stoneflies, wickerwork wings – can you see them in the main image?

Orthoptera         Grasshoppers and crickets, straight wings, referring to the sclerotised forewings that cover the membranous, sometimes brightly coloured hind wings.  Many people are surprised the first time they see a grasshopper flying as they have been taken in by the hopper part of the name and the common portrayal of grasshoppers in cartoons and children’s literature; or perhaps not read their bible “And the locusts went up over all the land of Egypt, and rested in all the coasts of Egypt”. I think also that many people don’t realise that locusts are grasshoppers per se.

Grasshopper wings

Dictyoptera        Cockroaches, termites and allies, net wings

Notoptera           The order to which the wingless Ice crawlers (Grylloblattodea) and Gladiators Mantophasmatodea) belong. Despite being wingless, Notoptera translates as back wings. It makes more sense when you realise that the name was coined when only extinct members of this order were known and they were winged.

Mantodea           Mantids, the praying mantis being the one we are all familiar with, hence the name which can be translated as prophet or soothsayer

Phasmotodea    Phasmids, the stick insects and leaf insects – phantom, presumably referring to their ability to blend into the background.

Psocoptera         Bark lice and book lice, gnawed or biting with wings. In this case the adjective is not in reference to the appearance of the wings, but that they are winged insects that can bite and that includes humans, although in my experience, not very painful, just a little itchy. They are also able to take up water directly from the atmosphere which means that they can exploit extremely dry environments.

Embioptera        Web spinners, lively wings. Did you know that Janice Edgerly-Rooks at Santa Clara University has collaborated with musicians to produce a music video of Embiopteran silk spinning? https://www.youtube.com/watch?v=veehbMKjMgw

Zoraptera            Now this is the opposite of the Notoptera, the Angel insects, Zora meaning pure in the sense of not having any wings.  Unfortunately for the taxonomists who named this order, winged forms have now been found 🙂

Thysanoptera    Thrips and yes that is both the plural and singular, thysan meaning tassel wings, although I always think that feather would be a much more appropriate description.

Feathery thrips wing – Photo courtesy of Tom Pope @Ipm_Tom

Hemiptera          True bugs – half wings.  The two former official suborders were very useful descriptions, Homoptera, e.g. aphids, the same. Heteroptera such as Lygaeids, e.g. Chinch bugs, which are often misidentified by non-entomologists as beetles where the prefix Hetero means different, referring to the fact that the fore wings are hardened and often brightly coloured in comparison with the membranous hind wings.

Coreid bug – Gonecerus acuteangulatus – Photo Tristan Banstock https://www.britishbugs.org.uk/heteroptera/Coreidae/gonocerus_acuteangulatus.html

Phthiraptera      The lice, the name translates as wingless louse. I guess as one of the common names for aphids is plant lice they felt the need to make the distinction in the name.

Siphonaptera     Fleas – tube without wings, referring to their mouthparts

 

Endopterygota

Rhapidioptera   Snakeflies – needle with wings, in this case referring to the ovipositor, not to the wings, which are similar to those of dragonflies.

The pointy end of a female snakefly

Megaloptera      Alderflies, Dobsonflies – large wings

Neuroptera        Lacewings – veined wings

Coleoptera         Beetles – sheathed wings, referring to the hardened forewings, elytra, that cover the membranous hind wings. The complex process of unfolding and refolding their hind wings means that many beetles are ‘reluctant’ to fly unless they really need to.

Strepsiptera       These are sometimes referred to as Stylops.  They are endoparasites of other insects. The name translates as twisted wings. Like flies, they have only two pairs of functional wings the other pair being modified into halteres.  Unlike flies, their halteres are modified fore wings.  Their other claim to fame is that they feature on the logo of the Royal Entomological Society.

The Royal Entomological Society Strepsipteran

Mecoptera         Scorpionflies, hanging flies – long wings.  Again, not all Mecoptera are winged, but those that are, do indeed have long wings in relation to their body size.

Male Scorpionfly, Panorpa communis.  Photo David Nicholls https://www.naturespot.org.uk/species/scorpion-fly

Siphonaptera     Fleas – tube no wings. The tube part of the name refers to their mouthparts.

Diptera                 Flies, two wings, the hind pair are reduced to form the halteres, which are a highly complex orientation and balancing device.

Trichoptera         Caddisflies, which are, evolutionarily speaking, very closely related to the Lepidoptera.  Instead of scales, however, their wings are densely cover with small hairs, hence the name hairy wings.  Some species can, at first glance, be mistaken for small moths. If you want to know more about caddisflies I have written about them here.

Lepidoptera       Moths and butterflies, scaly wings; you all know what happens if you pick a moth or butterfly up by its wings.

Moth wing with displaced scales

 

Hymenoptera    Wasps, bees, ants – membrane wings

Wing of a wood wasp, Sirex noctilio

 

And there you have it, all 30 extant insect orders in one easy location.

 

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A lost opportunity – why you should back up your data, even if it is on paper

In my twenty years at the Silwood Park campus of Imperial College, I supervised something in the order of 120 MSc research projects and at least 150 undergraduate final year projects.  Before my stint at Silwood Park I had spent ten years working for the Entomology Branch of the then UK Forest Research Division working on the population dynamics of forest pests.  My first ever PhD student, Paddy Walsh, (sadly he died a few years ago), worked on the predators associated with the pine beauty moth, Panolis flammea, with a particular interest in carabid beetles (Walsh et al., 1993ab). I was thus well aware of how useful pitfall traps were as a research tool; relatively easy to deploy and maintain and very good, perhaps too good, at collecting data 😊

Too much data? Pitfall traps – and contents waiting for identification (courtesy of former PhD student Lizzie Jones)

An early star of the pitfall trapping world was Penny Greenslade, who addressed the critical issue of what pitfall trap catches were actually measuring and concluded that they were only useful in a very limited set of conditions (Greenslade, 1964ab). Coincidentally, Penny Greenslade did her PhD at Silwood Park (Greenslade, 1961) and having found her very battered thesis in the Silwood Park Library it occurred to me that a re-sampling of her sites would make an ideal BSc or MSc research project and so it proved. In 1995, Andy Salisbury, an extremely keen undergraduate entomologist, now Principal Entomologist at RHS Wisley, was the first student to repeat her 1959 survey.  Over the years a succession of students resurveyed her original sites (they were clearly identifiable from her thesis, although the vegetation associated with the sites was, in some cases different from when she conducted her trapping. By the time I left Silwood Park for pastures new in 2012, there were eight BSc project dissertations reporting the results of re-sampling Penny Greenslade’s original sites sitting on the shelves of my lab.

I still had PhD students based at Silwood Park when I left, so for two years I was retained as a Visiting Professor, which, given how much stuff I had (you have all seen what my office looks like and my office at Silwood Park was no different 😊) meant that I moved stuff gradually and piecemeal.  I moved my collection of PhD theses (44 at the time) early on, but delayed moving the almost 300 undergraduate and MSc theses as I wanted to triage them at leisure and only transfer those that I felt might be of use.

Now we come to the tragic bit, the Director of Silwood Park decided that he wanted to refurbish the building that my former office and laboratory were in, and without telling me, had my laboratory cleared and the contents skipped. To say that I was annoyed is somewhat of an understatement. Unfortunately, I had none of these theses in electronic form so the data and the story that might have been told, are lost forever 😦

That said, not all the data are lost, I have a partial record of the 2007 BSc thesis by Sarah Stow which to a certain extent, rubs salt in the wound, as it shows that there were indeed changes in the carabid community composition since 1959.

 Three of Sarah’s figures showing changes in carabid communities and abundance

Although it might have been courteous if my former Head of Department had contacted me before disposing of the the project reports, or had them moved into storage to give me a chance of retrieving them, I can in all honesty, only blame myself for their loss.  I should have been less tardy in emptying my lab, I should have clearly indicated that I still had an interest in the contents of my lab, and of course, I should have backed up my data!

Not only data I am never going to publish but data I can’t ever publish ☹

References

Greenslade, P. J. M. (1961). Studies in the ecology of Carabidae (Coleoptera). Ph.D. thesis, University of London

Greenslade, P.J.M. (1964a) Pitfall trapping as a method for studying populations of Carabidae (Col). Journal of Animal Ecology, 33, 301-310.

Greenslade, P.J.M. (1964b) The distribution, dispersal and size of a population of Nebria brevicollis (F) with comparative studies on three other Carabidae. Journal of Animal Ecology, 33, 311-333.

Walsh, P.J., Day, K.R., Leather, S.R. & Smith, A.J. (1993a) The influence of soil type and pine species on the carabid community of a plantation forest with a history of pine beauty moth infestation. Forestry, 66, 135-146.

Walsh, P.J., Leather, S.R. & Day, K.R. (1993b) The effects of aerial application of fenitrothion on the carabid community of defoliated and undefoliated lodgepole pine, Pinus contorta. Journal of Applied Entomology, 115, 134-138.

 

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Pick and mix 21 – a cornucopia of links

There may actually be more Hymenoptera than there are Coleoptera!

Some book aren’t just for reading – wonderful hidden art

Fighting bats with long tails – moth evolution

Are you working on the right problem?

Bang, crackle, flash – Interesting paper about insect and arthropod names for fireworks

Inspired by the recent World Cup the John Innes Centre held their own version to champion discoveries they have made over the last 70 years 🙂

Insects through the Looking Glass – using Lewis Carroll to foster a love of insects

Victorian entomologists had a lot of fun – great post from Manu Saunders

A great post about science communication via Twitter by Stephen Heard

Spots on butterfly wings – what are they for?  Ray Cannon has some thoughts

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Global Insect Extinction – a never ending story

I have had an unexpectedly busy couple of weeks talking about declines in insect populations.  Back in November of last year I wrote a blog about the sudden media interest in “Insect Armageddon” and followed this up with a more formal Editorial in Annals of Applied Biology at the beginning of the year (Leather, 2018).  I mused at the time if this was yet another media ‘storm in a teacup’ but it seems that the subject is still attracting attention.  I appeared on television as part of TRT World’s Roundtable programme and was quoted quite extensively in The Observer newspaper on Sunday last talking about insect declines since my student days 🙂 At the same time, as befits something that has been billed as being global, a similar story, featuring another veteran entomologist appeared in the New Zealand press.

The TV discussion was quite interesting, the panel included Nick Rau from Friends of the Earth, Lutfi Radwan, an academic turned organic farmer, Manu Saunders from Ecology is Not a Dirty Word and me.  If they had hoped for a heated argument they were out of luck, we were all pretty much in agreement; yes insects did not seem to be as abundant as they had once been, and this was almost certainly a result of anthropogenic factors, intensive agriculture, urbanisation and to a lesser extent climate change.  Unlike some commentators who firmly point the finger at the use of pesticides as the major cause of the declines reported, we were more inclined to towards the idea of habitat degradation, fragmentation and loss.  We also agreed that a big problem is a lack of connection with Nature by large sections of the population, and not just those under twenty.  We also felt very strongly that governments should be investing much more into research in this area and that we desperately need more properly replicated and designed long-term studies to monitor the undeniable changes that are occurring.  I had, in my Editorial and an earlier blog post, mentioned this point and lamented the paucity of such information, so was pleasantly surprised, to receive a couple of papers from Sebastian Schuh documenting long-term declines in Hemiptera and Orthoptera in Germany (Schuh et al., 2012ab), although of course sad, to see yet more evidence for decreasing insect populations.

The idea that insects are in terminal decline has been rumbling on for some time; more than a decade ago Kelvin Conrad and colleagues highlighted a rapid decline in moth numbers (Conrad et al., 2006) and a few years later, Dave Brooks and colleagues using data from the UK  Environmental Change Network revealed a disturbing decline in the numbers of carabid beetles across the UK (Brooks et al., 2012).   In the same year (2012) I was asked to give a talk at a conference organised by the Society of Chemical Industry. Then, as now, I felt that pesticides were not the only factor causing the biodiversity crisis, but that agricultural intensification, habitat loss and habitat degradation were and are probably more to blame.  In response to this quote in the media at the time:

“British Insects in Decline

Scientists are warning of a potential ecological disaster following the discovery that Britain has lost around 7% of its indigenous insect species in just under 100 years.

A comparison with figures collected in 1904 have revealed that around 400 species are now extinct, including the black-veined white butterfly, not seen since 1912, the Essex emerald moth and the short-haired bumblebee. Many others are endangered, including the large garden bumblebee, the Fen Raft spider, which is only to be found in a reserve on the Norfolk/Suffolk border, and the once common scarlet malachite beetle, now restricted to just three sites.

Changes to the insects’ natural habitats have been responsible for this disastrous decline in numbers. From housing and industrial developments to single-crop farming methods, Britain’s countryside has become increasingly inhospitable to its native insects.”

I chose to talk about “Forest and woodland insects: Down and out or on the up?” I used data from that most valuable of data sets, the Rothamsted Insect Survey to illustrate my hypothesis that those insects associated with trees were either doing better or not declining, because of increased tree planting over the last fifty years.  As you can see from the slides from my talk, this does indeed seem to be the case with moths and aphids that feed on trees or live in their shade.  I also showed that the populations of the same species in northern Britain, where agriculture is less intensive and forests and woodlands more prevalent were definitely on the up, and this phenomenon was not just confined to moths and aphids.

Two tree aphids, one Drepanosiphum platanoidis lives on sycamore, the other Elatobium abietinum, lives on spruce trees; both are doing rather well.

Two more tree-dwelling aphids, one on European lime, the other on sycamore and maples, both doing very well.  For those of you unfamiliar with UK geography, East Craigs is in Scotland and Newcastle in the North East of England, Hereford in the middle and to the west, and Starcross in the South West, Sites 2, 1, 6 and 9 in the map in the preceding figure.

Two conifer feeding moth species showing no signs of decline.

On the up, two species, a beetle, Agrilus biguttatus perhaps due to climate change, and a butterfly, the Speckled Wood Pararge aegeria, due to habitat expansion and climate change?

It is important however, to remember that insect populations are not static, they vary from year to year, and the natural fluctuations in their populations can be large and, as in the case of the Orange ladybird, Halyzia sedecimguttata, take place over a several years, which is yet another reason that we need long-term data sets.

The Orange ladybird Halyzia sedecimguttata, a mildew feeder, especially on sycamore.

It is obvious, whether we believe that an ecological catastrophe is heading our way or not, that humans are having a marked effect on the biodiversity that keeps our planet in good working order and not just through our need to feed an ever-increasing population.  A number of recent studies have shown that our fixation with car ownership is killing billions of insects every year (Skórka et al., 2013; Baxter-Gilbert et al.,2015; Keilsohn et al., 2018) and that our fear of the dark is putting insects and the animals that feed on them at risk (Eccard et al.,  2018; Grubisic et al., 2018).  We have a lot to answer for and this is exacerbated by our growing disconnect from Nature and the insidious effect of “shifting baselines” which mean that succeeding generations tend to accept what they see as normal (Leather & Quicke, 2010, Soga & Gaston, 2018) and highlights the very real need for robust long-term data to counteract this dangerous and potentially lethal, World view (Schuh, 2012; Soga & Gaston, 2018).  Perhaps if research funding over the last thirty years or so had been targeted at the many million little things that run the World and not the handful of vertebrates that rely on them (Leather, 2009), we would not be in such a dangerous place?

I am, however, determined to remain hopeful.  As a result of the article in The Observer, I received an email from a gentleman called Glyn Brown, who uses art to hopefully, do something about shifting baselines.  This is his philosophy in his own words and pictures.

 

References

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

Brooks, D.R., Bater J.E., Clark, S.J., Monteith, D.T., 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 in insect biodiversity. Journal of Applied Ecology, 49, 1009-1019.

Conrad, K.F., Warren. M.S., Fox, R., Parsons, M.S. & Woiwod, I.P. (2006) Rapid declines of common, widespread British moths provide evidence of an insect biodiversity crisis. Biological Conservation, 132, 279-291.

Eccard, J.A., Scheffler, I., Franke, S. & Hoffmann, J. (2018) Off‐grid: solar powered LED illumination impacts epigeal arthropods. Insect Conservation & Diversity, https://onlinelibrary.wiley.com/doi/full/10.1111/icad.12303

Estay, S.A., Lima, M., Labra, F.A. & Harrington, R. (2012) Increased outbreak frequency associated with changes in the dynamic behaviour of populations of two aphid species. Oikos, 121, 614-622.

Grubisic, M., van Grunsven, R.H.A.,  Kyba, C.C.M.,  Manfrin, A. & Hölker, F. (2018) Insect declines and agroecosystems: does light pollution matter? Annals of Applied Biology,   https://onlinelibrary.wiley.com/doi/full/10.1111/aab.12440

Keilsohn, W., Narango, D.L. & Tallamy, D.W. (2018) Roadside habitat impacts insect traffic mortality.  Journal of Insect Conservation, 22, 183-188.

Leather, S.R. (2009) Taxonomic chauvinism threatens the future of entomology. Biologist, 56, 10-13.

Leather, S.R. (2018) “Ecological Armageddon” –  more evidence for the drastic decline in insect numbers. Annals of Applied Biology, 172, 1-3.

Leather, S.R. & Quicke, D.J.L. (2010) Do shifting baselines in natural history knowledge therten the environment? The Environmentalist, 30, 1-2.

Schuh, S. (2012) Archives and conservation biology. Pacific Conservation Biology, 18, 223-224.

Schuh, S., Wesche, K. & Schaefer, M. (2012a) Long-term decline in the abundance of leafhoppers and planthoppers (Auchenorrhyncha) in Central Europe protected dry grasslands. Biological Conservation, 149, 75-83.

Schuh, S., Bock, J., Krause, B., Wesche, K. & Scgaefer, M. (2012b) Long-term population trends in three grassland insect groups: a comparative analysis of 1951 and 2009. Journal of Applied Entomology, 136, 321-331.

Skórka, P., Lenda, M., Moroń, D., Kalarus, K., & Tryjanowskia, P. (2013) Factors affecting road mortality and the suitability of road verges for butterflies. Biological Conservation, 159, 148-157.

Soga, M. & Gaston, K.J. (2018) Shifting baseline syndrome: causes, consequences and implications. Frontiers in Ecology & the Environment, 16, 222-230.

 

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My group is bigger, better and more beautiful than yours – The annual MSc Entomology trip to the Natural History Museum, London, 2018

This week we went on one of my favourite trips with the MSc Entomology students.  We visited the Natural History Museum in London.  We got off to fantastic start – all the students, and staff, arrived at the arranged time of 0645, something that had never happened before :-). The weather was fine, although at that time in the morning it was too dark to really appreciate it, and off we set.  I should have known that something would go wrong and sure enough the traffic was awful, and we had to make an unscheduled stop at a motorway service station to make sure our driver didn’t exceed his quota of working hours.

The now much delayed coach basking in the sunshine at a motorway service station.

Some of the MSc students; remaining cheerful despite the delay.

Forty-five minutes later we set off again and despite encountering a few further delays arrived safely, albeit almost an hour and a half late.  Luckily our host for the day Erica McAlister (@flygirlNHM) was ready and waiting and very efficiently got our visit back on track.  This year we were shown Colossal Coleoptera by Michael Geiser, Huge Hymenoptera by Nathalie Dale-Skey, Lustrous Lepidoptera by Alessandro Giusi and Deadly Diptera by Erica McAlister.   All our specialist hosts were, as you would expect, very keen to extol the virtues of their groups, and who can blame them.  I do the same with Awesome aphids 🙂 We are always very appreciative of the time and care that the NHM entomologists give us, especially as they have, sadly, recently had their numbers reduced.  Hopefully, as the realities of the problems associated with insect conservation and identification become even more apparent than they already are, we will see the appointment of more entomologists to this very much-needed global resource.  Here are some pictures to give you a flavour of the day.

Mouse mat for forensic entomologists 🙂

Alessandro Giusti waxing lyrical about the biggest, the smallest and the most beautiful Lepidoptera (moths as far as he is concerned).

 

The large and the small (a really bad photo by yours truly, I am still getting to grips with my new camera)

Natalie Dale-Skey extolling the virtues of Hymenoptera

They don’t have to be big and tropical to be beautiful – these are tiny but gorgeous

I do like a good wasp nest 🙂

Erica McAlister on the sex life of flies

The biggest flies in the world pretending to be wasps

A selection of flies

I was very impressed that the Crane fly still has all its legs attached.  I collected Crane flies for my undergraduate collection and had to resort to sticking their legs on to a piece of card.

Not quite the rarest fly in the World but as its larvae live inside rhinoceroses it could be in trouble 😦

Big beautiful beetles

Cockchafers aren’t really this big, but wouldn’t it be awesome if they were?

MSc Entomology (@Entomasters) at the end of the visit.  Photo courtesy of Heather Campbell (@ScienceHeather), our newest member of staff

Once again, a huge vote of thanks to Erica and colleagues for making this a memorable visit.  We had a fantastic day.

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Battle of the Beetles – Kunoichi Beetle Girl – Maya Leonard Does it Again!

Battle of the Beetles, M.G. Leonard, 2018, Paperback, ISBN 9781910002780, Chicken House Publishing Ltd., Frome, UK.

I’m sad, I’m satisfied, I’m very impressed, I’m in a dilemma.  I’ve just finished reading Battle of the Beetles, the final instalment of M.G. Leonard’s Beetle Boy trilogy, which means, very sadly, that the adventure is over ☹

I’m satisfied, nay, very satisfied, because this final volume has lived up to the expectations raised by the previous two in the series, Beetle Boy and Beetle Queen.  I’m very impressed because Battle of the Beetles is so much more than an adventure story.  As well as being thrilling, heart-stopping, and full of action, it is also educational and raises some very important and thought-provoking issues.  I’m in a dilemma, because how can I review this excellent book without giving away spoilers?

First, just to reiterate this is a great book. It is a literary roller-coaster, featuring jungle escapades, martial arts, near-death experiences, family reunions, coleopteran gymnastics, terrifying events, pathos, bathos, scatological humour and a happy ending. In summary, a fantastic couple of hours entertainment.  If you have read the first two books in the series, you won’t be disappointed; buy or get someone to buy Battle of the Beetles for you as soon as possible.  If you haven’t read the earlier books you have some catching up to do 😊

The underlying theme of this instalment is metamorphosis and physiology and be warned there is some very memorable and slightly disturbing imagery connected with these themes.  You will never see Silphids (carrion beetles) in the same way again. Speaking of imagery, the illustrations by Karl James Mountford are stunning.  While amusing and entertaining there are some very serious underlying concepts that hopefully will not be overlooked by readers.  We learn about environmentally friendly means of pest control, e.g. pheromone disruption and the very successful and relevant real-life Sterile Insect Techniques (SIT). SIT was pioneered as a control technique against the screw worm, a serious pest of cattle in the USA (Baumhover et al., 1955; Knipling, 1955) and is now seen as a practical way forward for mosquito control or eradication (Benelli, 2015).  This may however, be the first time it has been mentioned in a work of fiction for children. Another first for Maya Leonard 🙂 The lack of undergraduate entomological training in the UK also gets a mention; the good news is that the MSc in Entomology at Harper Adams University is shortly to be joined by a new undergraduate degree, Zoology with Entomology 😊

The most thought-provoking theme is, however, that of rewilding, much in the news these days.  How far would you be willing to go to conserve species and protect the environment?  At one stage I almost felt sympathetic towards Lucretia Cutter; a truly brilliant twist to the story.  I don’t think I can say much more without giving too much away.

Embrace your inner beetle, throw away your prejudices and enjoy this fantastic adventure.  An enthralling read for everyone aged nine and above, including entomologists and ecologists.

References

Baumhover, A.H., Graham, A.J., Bitter, B.A., Hopkins, D.E., New, W.D., Dudley, F.H. & Bushland, R.C. (1955) Screw-worm control through release of sterilized flies.  Journal of Economic Entomology, 48, 462-466.

Benelli, G. (2015) Research in mosquito control: current challenges for a brighter future. Parasitology Research, 114, 2801-2805.

Knipling, E.F. (1955) Possibilities of insect control or eradication through the use of sexually sterile males. Journal of Economic Entomology, 48, 459-462.

 

Post script

I must also compliment Maya and her copy editor.  This is one of the most typo-free books I have read for some time.  I only found one error/typo, bearing used instead of baring.  Excellent proof reading.

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Entomological classics – the sweep net

I am certain that everyone who has studied biology at university and/or been on a field course, will have used a sweep net and heard the phrase “It’s all in the wrist”.  Along with the pitfall trap it is the most commonly used entomological sampling technique used today.  Although the premise is simple enough, a sturdy net, attached to a handle that is swept along, through or above low-lying vegetation, when used as a scientific tool and not just as a collecting device, things become somewhat more complex.  The sweep net, as an insect collecting device, has been around for at least 180 years, the earliest reference that I have been able to find being Newman* (1835).  There are a number of slightly later references in both general entomology texts and group specific books (e.g. Newman, 1844; Clark, 1860; Douglas, 1860; Douglas & Scott, 1865). Instructions for their use at this time are minimal, as this extract from Newman (1841) illustrates.

Newman (1841) a very brief description indeed.

This slightly later description of how to make a sweep net is, however, much more detailed, albeit somewhat sexist.

From Stainton (1852), although he seems to be quoting Newman.  Apparently Victorian men were unable to sew.

More detailed, albeit fairly basic instructions on how to use a sweep net can be found in those two invaluable sources, Ecological Methods (Southwood & Henderson 2004) (two pages) and Practical Field Ecology (Wheatear et al., 2011) (one page).  I was amused to see that the text in Southwood & Henderson was identical to that of the first edition (Southwood, 1966).

Now we come to the wrist action. There are a surprising number of ways in which you can swing a sweep net, but they all depend on the wrist moving your hand, and hence the net, in a figure of eight. The two most commonly used are what I think of as the one row side step, and the double front step.  In the former you walk in a straight line swinging the net backwards and forwards at your side, ideal for sampling a row crop. The latter, the double front step, is similar, but instead of swinging the net at your side, you swing it side to side in front of you as you walk along.  In a crop, this is great for sampling multiple rows, in a non-crop a good way of covering a nice wide area of vegetation. There are a further two techniques specifically designed for sweeping the upper part of vegetation, both originally devised for sampling soybean insects, the lazy-8 and the pendulum (Kogan & Pitre, 1980).  Both these involve having the net raised, the lazy-8 with the net raised above the crop at the back and front swings, whereas in the pendulum, the net is kept within the crop on the fore and reverse swings.  The final bit of wrist action, and arguably the most important and difficult to learn, is the flick-lock, which neatly seals the net and stops your catch escaping.

Having completed your sample of however many sweeps (remember a complete sweep is the figure of eight), and sealed your net, the next step is to transfer your catch to your collecting tubes, bags or jars.  A good sweep net, as well as being made from tough material, should be a bit sock shaped.  By this I mean that there is a ‘tail’ at the base of the net which helps make your catch more manageable if you are transferring directly to a plastic bag, as you are able to grab the net above the ‘tail’ end and push it into the collecting bag, before everting the net.

Two examples of sweep nets, a large and a small one.  You can also get a medium one in this series supplied by the NHBS web site for about £34. http://www.nhbs.com/professional-sweep-net

When I was a student, the sweep nets we were supplied with, were large enough to stick not just your head inside, but also to get your arms in, so that you could Poot up anything interesting, your shoulders forming the seal to the net.  Admittedly you did sometimes have an angry bee or wasp to contend with, but that was a rare event 🙂  Nowadays, sweep nets seem to be constructed on a much more modest scale, which makes sticking your head, let alone your shoulders into one, somewhat difficult.

Even the biggest modern one is too small for me to get my arms in to do some Pooting.

I was pleasantly surprised on an ERASMUS exchange visit to the University of Angers a few years ago, to find that the French, or at least those in Angers, were using sweep nets that were big enough for me to actually delve inside just as I did when I was a student 🙂

The joys of a sweep net with a view 🙂

Despite their undoubted popularity, value for money and relative ease of operation, there are a number of problems associated with sweep netting as a sampling technique.  Although these problems are summarised elsewhere (Southwood & Henderson 2004; Wheater et al., 2011) I can’t resist putting my own personal slant on the subject.

  • The type of habitat can have a marked effect on what you catch. Not all habitats are equally amenable to sweeping; spiny and woody vegetation poses more problems than a nice meadow and you need a really tough net for moorlands 🙂
  • A sweep net doesn’t necessarily give you an accurate picture of the species composition of the habitat. Not all insects are equally catchable, you are for example, much more likely to catch Hemipterans than you are Coleopterans (e.g. Standen, 2000)
  • The vertical distribution of the insects also affects what you catch. Many insects have favourite positions on plants e.g. the cereal aphid, Sitobion avenae prefers the ears and leaves, whereas the bird cherry-oat aphid, Rhopalosiphum padi is usually found at the bottom of the plant (Dean, 1974).
  • The weather; anyone who has tried sweep netting during, or after, a rain storm knows that this is the ultimate act of folly 🙂 Wet nets and wet samples are not a marriage made in heaven.
  • Time of day can also affect what you are likely to catch, pea aphids for example, are found at different heights on their host plants at different times of day (Schotzko & O’Keeffe, 1989). To be fair, this is of course not just a problem confined to sweep net sampling.
  • Sweep nets have a fairly well-defined height range at which they work best, they are not good at sampling very short grass and once the vegetation gets over 30 cm you start to miss a lot of the insects associated with it as the net doesn’t reach that far down. Also the efficiency of the sweep netter is reduced.
  • Finally, how the hell do you standardise your sweeps, not only between sweepers, but as an individual? Additionally, can you reliably use them quantitatively? This has been recognised as a problem for a long time (DeLong, 1932).  No one disagrees that sweep netting, provided all the caveats listed above are taken into account, gives a very good qualitative and comparative idea of the arthropod community of the area you are sweeping and they have been so used in many important ecological studies (e.g. Menhinick, 1964; Elton, 1975; Janzen & Pond, 1975) and extensively in agricultural systems (e.g. Free & Williams, 1979; Kogan & Pitre, 1980).  Comparing any sampling technique with another is difficult, and any attempt to quantify a catch so that specific units can be assigned to the area or volume sampled is welcome.  This has been attempted for the sweep net (Tonkyn, 1980), although I confess that I have never seen anyone use the formula developed by him.  In fact, although, according to Google Scholar his paper has been cited thirteen times, only one of the citing authors actually uses the formula, the rest just use him to cite sweep netting as a sampling method. Poor practice indeed.

An illustration of how the various components of the sweep net volume formula is derived (from Tonkyn, 1980).

Sweep nets are, despite the inability to get inside them anymore, great fun to use, extremely good at collecting material for ecology and entomology practicals and of course, a great ecological survey tool when used properly.  Google Scholar tells me that there are over 38 000 papers that mention them.  That many people can’t possibly be wrong 🙂

References

Clark, H. (1860) Catalogue of the Collection of Halticidae in the British Museum. Physapodes and Oedipodes Part 1. Published by the Trustees, London.

Dean, G.J. (1974) The four dimensions of cereal aphids. Annals of Applied Biology, 77, 74-78.

DeLong, D.M. (1932) Some problems encountered in the estimation of insect populations by the sweeping method.  Annals of the Entomological Society of America, 25, 13–17.

Douglas, J.W.  (1856) The World of Insects: A Guide to its Wonders. John van Voorst, London.

Douglas, J.W. & Scott, J. (1865) The British Hemiptera Volume I Hemiptera – Heteroptera. Ray Society, Robert Hardwicke, London.

Elton, C.S. (1975) Conservation and the low population density of invertebrates inside neotropical rain forest.  Biological Conservation, 7, 3-15.

Free, J.B. & Williams, I.H. (1979) The distribution of insect pests on crops of oil-seed rape (Brassica napus L.) and the damage they cause. Journal of Agricultural Science, 92, 139-149.

Janzen, D.H. & Pond, C.M. (1975) A comparison, by sweep sampling, of the arthropod fauna of secondary vegetation in Michigan, England and Costa Rica. Transactions of the Royal Entomological Society of London, 127, 33-50.

Kogan, M. & Pitre, H.N. (1980) General sampling methods for above-ground populations of soybean arthropods. Pp 30-60 [In] Sampling Methods in Soybean Entomology. (Eds.) M. Kogan & D.C. Herzog, Springer, New York.

Menhinick, E.F. (1964) A comparison of some species-individuals diversity indices applied to samples of field insects. Ecology 45, 859-861.

Newman, E. (1844) The Zoologist. A Popular Miscellany of Natural History, Volume 2. John van Voorst, London.

Newman, E. (1841) A Familiar Introduction to the History of Insects. John van Voorst, London.

Newman, E. (1835) The Grammar of Entomology. Frederick Westley & A.H. Davis, London.

Schotzko, D.J. & O’Keeffe, L.E. (1989) Comparison of sweep net., D-Vac., and absolute aampling., 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. (1966) Ecological Methods, Methuen & Co., London.

Stainton, H.T. (1852) The Entomologist’s Companion; Being a Guide to the Collection of Microlepidoptera and Comprising a Calendar of the British Tineidae. John van Voorst, London.

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

Tonkyn, D.W. (1980) The formula for the volume sampled by a sweep net.  Annals of the Entomological Society of America, 73,452-454.

Wheater, P.C., Bell, J.R. & Cook, P.A. (2011) Practical Field Ecology: A Project Guide, Wiley-Blackwell, Oxford.

 

*Of interest to me, but perhaps not to my readers, Edward Newman was one of the founder members of the oldest and most exclusive, yet low-key, entomological society in the world, The Entomological Club, of which I have the honour of being a member 😊 https://en.wikipedia.org/wiki/Edward_Newman_(entomologist)  founder member of the Entomological Club

 

 

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An inordinate fondness for biodiversity – a visit behind the scenes at the Natural History Museum

Last week  (13th February) I traveled with the MSc Entomology students to the Natural History Museum, London.  As part of their course they are taken behind the scenes and meet some of the curators and their favourite beasts.  This one of my favourite course trips and although I have made the pilgrimage for many years I always find something new to marvel at as well as reacquainting myself with some of my old favourites.  After an early start (0645) we arrived exactly on time (for a change), 10.30, at the Museum site in South Kensington.  I always have mixed feelings about South Kensington, having spent twenty years of my life commuting to Imperial College, just up the road from the museum.  I loved teaching on the Applied Ecology course I ran, but over the years the working atmosphere in the Department became really toxic* and I was extremely glad to move to my present location, Harper Adams University.  After signing in, which with twenty students took some time, Erica McAlister (@flygirl) led us through the thronged galleries (it was half term) to the staff

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Nostalgia time, my first biological memory, aged 3.

areas, where the research, identification and curating takes place.  Our first port of call was the Diptera where Erica regaled us with lurid tales of flies, big and small, beneficial and pestiferous.

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Erica McAlister extolling the virtues of bot flies

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Any one fancy cake for tea?  Kungu cake, made from African gnats

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Early advisory poster

As we left to move on to the Hymenopteran, hosted by David Notton, I noticed this classic poster warning against mosquitoes.  David chose bees as the main focus of his part of the tour, which as four of the students will be doing bee-based research projects was very apt.

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Admiring the bees

Whilst the students were engrossed with the bees I did a bit of fossicking and was amused to find that tobacco boxes were obviously a preferred choice by Scandinavian Hymenopterists in which to send their specimens to the museum.

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Finnish and Swedish tobacco boxes being put to good use

Next was that most eminent of Coleopterists, Max @Coleopterist Barclay who as usual enthralled the students and me, with stories of

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Max Barclay demonstrating a Lindgren funnel and talking about ‘fossilised’ dung balls

beetles large and small, anecdotes of Darwin and Wallace and the amusing story of how ancient clay-encased dung balls were for many years thought by anthropologists and archaeologists to be remnants of early humankind’s bolas hunting equipment.  It was only when someone accidentally broke one and found a long-dead dung beetle inside that the truth was revealed 🙂

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Often overlooked, the Natural History Museum is an exhibit in itself

 As we were leaving to move on to the Lepidoptera section, I felt obliged to point out to the students that not only is the outside of the museum stunningly beautiful but that the interior is also a work of art in itself, something that a lot of visitors tend to overlook. Once in the Lepidoptera section  Geoff Martin proudly displayed his magnificent collection of Lepidoptera, gaudy and otherwise, including the type specimen of the Queen Alexandra’s Birdwing which was captured with the aid of a shotgun!

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Lepidopterist, Geoff Martin, vying with his subjects in colourful appearance 🙂

Lunch and a chance to enjoy the galleries was next on the agenda.  Unfortunately, as it was half term this was easier said than done, although I did find a sunny spot to eat my packed lunch, as a Yorkshireman I always find the prices charged for refreshments by museums somewhat a painful.  In an almost deserted gallery I came across this rather nice picture.

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A lovely piece of historical entomological art.

Then it was on to the Spirit Collection.  Erica had laid on a special treat, Oliver Crimmen, fish man extraordinaire.  I may be an entomologist but I can sympathise with this branch of vertebrate zoology.  Fish, like insects are undeservedly ranked below the furries, despite being the most speciose vertebrate group.  I have been in the Spirit Room many times but have never seen inside the giant metal tanks.  Some of these, as Ollie demonstrated with a refreshing disregard for health and safety, are filled with giant fish floating in 70% alcohol.

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Fish man, Oliver Crimmen, literally getting to grips with his subjects.

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A fantastic end to the day culminated with a group photo with a spectacular set of choppers 🙂

Many thanks to Erica McAlister for hosting and organising our visit and to the NHM staff who passionately attempted to convert the students to their respective ‘pets’.

*one day I will write about it.

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Baxter Saves the Day – Beetle Boy – a tour de force by M G Leonard

Beetle Boy front

Beetle Boy, Chicken House Books, Paperback  ISBN: 9781910002704  £6.99

 “The sad fact is, that the number of insect is in decline. As we destroy their habitats, so we destroy their species, but we desperately need them. If all the mammals on the planet were to die out, the planet would flourish – but if all the insects disappeared, everything would very soon be dead.”

Not that I am biased, but any book that has the above in it gets my vote. Joking aside, this is a real gem of a book.  Although aimed at a younger audience than me, I found this a fascinating book.  I read it in one sitting, on the coach returning from a visit to the entomologists at the Natural History Museum, in company with the MSc Entomology students from Harper Adams University; a very appropriate setting.

Darkus, whose father, Dr Bartholomew Cuttle, a closet entomologist and the Director of Science at the Natural History Museum in London, has disappeared in mysterious circumstances, is one of a pair of unlikely heroes who help make this story the tour de force it is. The authorities believe that Dr Cuttle suffered some sort of breakdown and has walked away from his responsibilities.  Newspaper headlines ensue and the distraught Darkus, who remains convinced that his father has been spirited away or worse, now regarded as an orphan by social services, as his mother died four years earlier, is sent to an orphanage where he receives an unfortunate hair-cut.  Fortuitously, three weeks later, his eccentric Uncle Max, a somewhat unconventional archaeologist, returns from Egypt and Darkus is allowed to move in with his Uncle, who houses him in his attic, where he unknowingly meets his best friend to be, Baxter, and the adventure begins.  You will have to excuse this breathless introduction, but all this happens in the first sixteen pages!  What a roller-coaster of a read.

Next he is sent to a new school, (the worst nightmare for those of us of a nerdish persuasion) where he is befriended by two odd-balls, the lanky Virginia and the small, pale, bespectacled Bertholt.  We have school bullies, beetles with more than a dash of humanity mixed in, an evil businesswoman with a dark past and even darker secrets, a beautiful heiress thrown in for good measure, very odd neighbours, a secret den, evil henchmen, poison gas, death, destruction, entomology, successes, setbacks, laughter and sadness but a happy ending.  This is a story with something for everyone.  This is what my father, if he were still alive, would have called a rattling good yarn and I would agree with him wholeheartedly.

This is a hard book to describe without introducing spoilers so I am not going to give away any more of the plot than I already have. Imagine a mix of Swallows & Amazons, Stalky & Co*, the Famous Five, Five Find-Outers and Dog**, Artemis Fowl and any other of your favourite young detectives/adventurers that you can think of, and you will get somewhere close to imagining what a gripping read Maya Leonard has produced.   Beetle Boy owes nothing to any of these books, I only use them to illustrate, that in my opinion, this book is destined to join the classics.

It is of course the beetles that really make this book stand out from the crowd, and in more than one way, the fore edge of the book is decorated with beetles; beetles inside and out, what more can an entomologist ask for?

Beetle boy fore edge

Maya Leonard is a superb ambassador for beetles; they form an integral part of the story working in partnership with the human protagonists. She also subtly introduces the wonderful diversity of the beetle world to the non-initiated.  How many books can mention tiger beetles, powder post beetles, blister beetles, bombardier beetles, rhinoceros beetles, titans, stags, harlequins,  Goliath beetles and dung beetles and keep the plot moving along at a breath-taking pace.  Outside an entomology text book I don’t think I have ever come across so many beetle references.   Not only has Maya Leonard mentioned the beetles by name, she has managed to endow them with believable personalities but in a very unsentimental way, although that said, there is a very tragic scene near the end of the book.   I have been a professional entomologist for almost forty years and, yes some of what happens in this book might not be entomologically feasible, but the story carried me along on waves of excitement and totally enthralled and enchanted me and that is what matters.  I liked this book very much.  In fact, I was so excited about this book that I couldn’t wait for an appropriate grandson’s birthday so sent it to their mother, my daughter in Australia, for her birthday, and suggested that she could make it a family readathon 🙂

Maya Leonard, on the behalf of entomologists everywhere, I salute you. Roll on the sequel.

Dung beetles ZSL

The wonderful dung beetle sculpture at London Zoo.

Postscript and notes

Did I say that I really liked this book 🙂

*Rudyard Kipling’s fictionalised account of his school days at the United Services College – coincidentally, the character based on Kipling, is nicknamed Beetle! Well worth a read and in my opinion, possibly the inspiration for Frank Richard’s Billy Bunter books.

**Less well-known than the Famous Five, but I actually liked them better 🙂 http://www.enidblytonsociety.co.uk/five-find-outers.php

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Ten Papers that shook my World – Root (1973) – When more means less – crop diversity reduces pest incidence

I can’t remember when I first read this paper but judging by the record card and the state of the actual hard copy of the paper, it was probably when I was doing my PhD in the late 1970s. This paper and its companion, which was published a year earlier* (Tahvanainen & Root, 1972), have had a significant effect on the scientific understanding and development of inter-cropping as a method of crop protection worldwide. Although inter-cropping in some form or another has been around a long time, the idea that it could be used as part of an integrated pest management programme was not proven.  In this landmark study, Root compared pure stands (plots) of collards (spring greens in the UK) (Brassica olercaea) with adjacent rows of collards grown intermingled with other herbaceous plants.  His premise being that it was well documented that pest outbreaks tend to be associated with pure monocultures of crops (Pimentel, 1961; Janzen, 1970) and he wished to test the hypothesis that natural enemies were more abundant and effective in vegetationally diverse areas  than in pure monocultures, the so-called ‘enemies hypothesis’.  This idea had been around a surprisingly long time e.g. Ullyett (1947) who remarked  “where weeds occur around headlands and in hedges, they should be left for the purpose of supporting parasites and predators important in the natural control of the diamond-back moth (Plutclla maculipennis Curt)”.  A decade later, Elton (1958,) refers to this statement, explaining that “these hedge rows form a reservoir for enemies and parasites of insects and mite pests of crops”.  I am not sure what it indicates but note that many groups around the world, including mine, are still working on this both at the local (field-scale) level (e.g. Ramsden et al., 2014) and landscape level (e.g. Rusch et al., 2013; Raymond et al., 2015).

Root explained the premise of the ‘enemies hypothesis’ as follows.  Predators and parasites are more effective at controlling herbivore populations in diverse habitats or plant communities because, diverse plant communities support a diversity of herbivores with a variety of phenologies, providing a steady supply of prey for the predators.  In addition, complex environments provide prey refugia, thus allowing the prey not to be completely eradicated.  Diverse plant communities also provide a broad range of additional resources for adult natural enemies e.g. pollen and nectar.

Root ran his experiment for three years and did indeed find a significant difference in herbivore load between the pure plots and the weedy rows, the former having a greater abundance of pests (mainly aphids and flea beetles) than the latter.

Fig 1

From Root (1973)

To his disappointment (I assume), he did not find any difference in the numbers of natural enemies between the two treatments. He thus had to come up with another idea to explain his results. His ingenious explanation is encapsulated in what he termed the Resource concentration hypothesis which states that herbivores are more likely to find and stay on hosts growing in dense or nearly pure stands and that the most specialised species often reach higher relative densities in simple environments.

Fig 2

Typical modern monocultures, beans, cabbages and wheat

He hypothesised that specialist herbivores were ‘trapped’ on the crop and accumulated whilst more generalist herbivores were able to and likely to move away from the crops to other host plants.  Root added that the ‘trapping effect’ of host patches depends on several factors such as stand size and purity.

In 1968, presumably as a result of what Root was discovering, Jorma Tahvanainen (one of the many great Finnish entomologists who appeared on the scene in the 1970s -, he retired in 2004) came to Cornell to do his PhD with Richard Root. Working on the same system and in the same meadow, Tahbanainen developed two new hypotheses to explain why more diverse cropping systems have fewer pest problems than monocultures. His experiments as he too found little evidence of natural enemies having an effect. He developed two new hypotheses, one he termed Associational resistance which I reproduce below exactly as published:

A natural community, such as a meadow, can be treated as a compound system composed of smaller, component communities (Root, 1973). The arthropods associated with different plant species represent important components in terrestrial systems. The available information indicates that the biotic, structural and microclimatic complexity of natural vegetation greatly ameliorates the herbivore pressure on these individual components, and consequently, on the system as a whole. Thus, it can be said that in a compound community there exists an “associational resistance” to herbivores in addition to the resistance of individual plant species. If the complex pattern of natural vegetation is broken down by growing plants in monocultures, most of this associational resistance is lost. As a result, specialized herbivores which are adapted to overcome the resistance of a particular plant species, and against which the associational resistance is most effective, can easily exploit the simplified system. Population outbreaks of such herbivores are thus more likely to occur in monocultures where their essential resources are highly concentrated

The other, is the Chemical Interference Hypothesis, in which he postulated that reduced herbivory in diverse communities due to chemical stimuli produced by non-host plants interfering with host finding or feeding behaviour of specialist herbivores.  His experimental set-up was very simple, but very effective.

Fig 3

How to send mixed signals to specialist herbivores – reproduced from Tahvanainen & Root (1972)

In simple terms, a monoculture sends out a very strong signal, it could be olfactory, e.g. a strong bouquet of crucifer volatiles, or for other herbivores it could be visual, or a combination of the two.

Fig 4

Conventional intensive agricultural landscape sending out strong ‘signals’ to specialist herbivores

Inter-cropping increases crop diversity and changes the crop ‘signal’ to one that now ‘confuses’ specialists. Note that I am not necessarily advocating a combined crop of wheat, beans and cabbages, as harvesting would be a nightmare 😉

Fig 5

 

The intercrop melange effect

These two papers have had a huge influence on the theory and practice of inter-cropping and agricultural diversification, although Root (1973) has had many more citations (1393 according to Web of Science on 11th December 2015) than Tahvanainen & Root (1972) which has only had a meagre 429 citation to date.  The message coming out from the many studies that have now investigated the effect of intercropping crop diversification on pest abundance, is, that in general, polyculture is beneficial in terms of promoting biological control and that incorporating legumes into the system gives the best yield outcomes (Iverson et al,  2014).

Another take on intercropping that overcomes the potential problems of harvesting different crops from the same field, is the concept of planting different genotypes of the same species. Resistant plants tend to have fewer generalists present, although their individual yield may be reduced.  By planting a mixture of susceptible and resistant genotypes it is however, possible to have your cake and eat it, especially if it is not essential to have a single genotype crop.  This approach has been used to good effect in the production of short rotation willow coppice, where planting diverse genotypes of the same species reduces both pest and disease levels (Peacock et al., 2000, 2001).

Who would have that two simple field experiments conducted in an abandoned hay meadow outside Ithaca, New York almost fifty years ago would have such a far-reaching influence?

 

References

Elton, C. S. (1958) The Ecology of Invasions by Animals and Plants. London: Methuen & Co., Ltd. 159 pp.

Iverson, A. L., Makin, L. E., Ennis, K. K., Gonthier, D. J., Connor-Barrie, B. T., Remfret, J. L., Cardinale, B. J. &Perfecto, I. (2014). Do polycultures promote win-win or trade-offs in agricultural ecosystem services? A meta-analysis. Journal of Applied Ecology. 51, 1593-1602.

Peacock, L. & Herrick, S. (2000) Responses of the willow beetle Phratora vulgatissima to genetically and spatially diverse Salix spp. plantations. Journal of Applied Ecology, 37, 821-831.

Peacock, L., Hunter, T., Turner, H., & Brain, P. (2001) Does host genotype diversity affect the distribution of insect and disease in willow cropping systems? Journal of Applied Ecology, 38, 1070-1081

Janzen, D.H. (1970) The unexploited tropics.  Bulletin of the Ecological Society of America, 51, 4-7

Pimentel, D. (1961). Species diversity and insect population outbreaks. Annals of the Entomological Society of America, 54, 76-86.

Ramsden, M. W., Menéndez, R., Leather, S. R. & Wackers, F. (2014). Optimizing field margins for biocontrol services: the relative roles of aphid abundance, annual floral resource, and overwinter habitat in enhancing aphid natural enemies. Agriculture Ecosystems and Environment, 199, 94-104.

Raymond, L., Ortiz-Martinez, S. A. &Lavandero, B. (2015). Temporal variability of aphid biological control in contrasting landscape contexts. Biological Control , 90, 148-156.

Root, R. B. (1973). Organization of a plant-arthropod association in simple and diverse habitats: the fauna of collards. Ecological Monographs, 43, 95-124.  1393 citations

Rusch, A., Bommarco, R., Jonsson, M., Smith, H. G. &Ekbom, B. (2013). Flow and stability of natural pest control services depend on complexity and crop rotation at the landscape scale. Journal of Applied Ecology, 50, 345-354.

Tahvanainen, J. & Root, R. B. (1972). The influence of vegetational diversity on the population ecology of a specialized herbivore Phyllotreta cruciferae (Coleoptera: Chrysomelidae). Oecologia, 10, 321-346. 429 citations

Ullyett, G. C. (1947) Mortality factors in populations of Plutella maculipennis Curtis (Tineidae: Lep.) and their relation to the problem of control. Union of South Africa, Department of Agriculture and Forestry, Entomology Memoirs, 2, 77-202.

Post script

*I suspect, judging by how the two papers cite each other, that the Root (1973) paper was actually submitted first but that the vagaries of the publication system ,  meant that follow-up paper, Tahvanainen & Root (1972) appeared first.

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Filed under Entomological classics, Ten Papers That Shook My World