Green islands for the third and final time?

I have regaled you with tales of green islands twice before, first in relation to trees miraculously surviving mass defoliation events, and second, in terms of leaf miners and their exploitation of cytokinins.  This time it is the turn of the cowpat islets to make their appearance.  Those of you who are lucky enough to be able to walk in the countryside will probably have noticed that some of the fields you walk through are dotted with lots of clumps of longer grass and perhaps wondered what they are and why they are there.

A recently grazed pasture, showing very clear cowpat islets (Sutton, Staffordshire May 2021).

 If you look early enough or carefully later on, you will see that these clumps are associated with cowpats.  There have been a lot of theories about why these clumps arise, ranging from increased plant nutrition (Taylor & Rudman, 1966), after all we put manure on our gardens to improve plant growth, to unpalatability of the grass due to raised sugar levels (Plice, 1951).  This latter idea has since been dismissed, although the fact that cattle avoid feeding on these clumps has been well documented (Merten & Donker, 1964).  There is another explanation for why cattle avoid grazing near cowpats. You may not know it, but despite the fact that cattle don’t seem to have much control (or perhaps they just don’t care) over when and where they deposit their excreta, but cattle, despite the behaviour of bullocks, aren’t stupid. Just like you and me, they aren’t that keen on eating their own and other people’s sh*t.  A good reason for avoiding eating excreta, whether your own or someone else’s, is that areas contaminated with dung are associated with higher numbers of gastro-intestinal parasites (Boom & Sheath, 2008; Gethings et al., 2015), so it makes very good sense to avoid eating contaminated grass.  Whatever the reason, be it increased nutrition or distastefulness, the result is clumps of longer grass dotted around the pasture taking up between 20 and 30% of the field (Taylor & Rudman, 1966).

You may, by now, be wondering why an entomologist is going on about cowpats and grass clumps. Well, as you all know, in my world, everything comes round to entomology 🙂 It has been known for some time that hedges and hedgerows provide refuges for insects, admittedly, not all beneficial ones (Lewis, 1969; D’Hulster, M. & Desender, 1982), but nevertheless, an observation that led to the development of beetle banks and conservation headlands (Sotherton et al., 1989; Thomas et al., 1991). It is, however, not just field boundaries that can provide habitats for insects. Belgian coloepterist, the late Konjev Desender and colleagues, found that the sward islets provided extra overwintering sites for staphylinid beetles, which provide an important role in natural pest regulation (D’Hulster & Desender, 1984).  Strangely, well to me anyway, interest in the entomological role of sward islets died a death.  It wasn’t until almost thirty years later that a former colleague of mine, keen hemipterist Alvin Helden (now at Anglia Ruskin University), and colleagues, found that sward islets were also proving very important refugia for grassland Hemiptera and lycosid and linyphid spiders (Helden et al., 2010: Dittrich & Helden, 2012). Before the grazed sward recovered the islets, which in their study occupied 24% of the pasture, hosted about 50% of the total arthropod community.  So a very important role in conserving biodiversity within agroecosystems, but despite this very important finding, sward islet entomology has yet again fallen off the entomological radar 😦

Less recently grazed pasture, but cowpat islets still visible within the recovering sward (Sutton, Staffordshire, May 2021) but still, according to Alvin Helden, containing a higher density of arthropods than the surrounding grazed area (Helden et al., 2010).

I think that revisiting the ecology of sward islets would prove very rewarding for both MSc and PhD projects.  Off the top of my head I can come up with a couple of projects; for a PhD, given that the fertilisation level and type affected the relative abundance of two of the Hemipteran families, Delphacids and Cicadellids (Dittrich & Helden, 2012), a comparison of the fauna and flora of sward islets on conventional and organic farms would make a really rewarding project. Harking back to my interests in island biogeography a study of the size, floral composition, structure and distribution of sward islets and how this affects arthropod communities would make a neat MSc project or perhaps even another PhD.

I am sure that with a little bit of thought, many more projects, not just entomological could be devised. Over to you dear readers.

References

Boom, C.J. & Sheath G.W. (2008) Migration of gastrointestinal nematode larvae from cattle faecal pats onto grazable herbage. Veterinary Parasitology, 157, 260-266.

D’Hulster, M. & Desender, K. (1982) Ecological and faunal studies on Coleoptera in agricultural land III. Seasonal abundance and hibernation of Staphylinidae in the grassy edge of a pasture. Pedobiologia, 23, 403–414.

D’Hulster, M. & Desender, K. (1984) Ecological and faunal studies of Coleoptera in agricultural land IV. Hibernation of Staphylinidae in agro-ecosystems. Pedobiologia, 26, 65–73.

Dittrich , A.D.K. & Helden, A.J. (2012) Experimental sward islets: the effect of dung and fertilisation on Hemiptera and Araneae. Insect Conservation and Diversity, 5, 46–56.

Gethings, O.J., Sage, R.B. & Leather, S.R. (2015) Spatio-temporal factors influencing the occurrence of Syngamus trachea within release pens in the south West of England. Veterinary Parasitology, 207, 64-71.

Helden, A.J., Anderson, A., Sheridan, H. & Purvis, G. (2010) The role of grassland sward islets in the distribution of arthropods in cattle pastures. Insect Conservation and Diversity, 3, 291–301.

Lewis, T. (1969) The diversity of the insect fauna in a hedgerow and neighbouring fields. Journal of Applied Ecology, 6, 453-458.

Marten, G.C. &  Donker, J.D. (1964) Selective grazing induced by animal excreta. II. Investigation of a causal theory. Journal of Dairy Science, 47, 871-874.

Plice, M. J. (1951) Sugar versus the intuitive choice of foods by livestock. Agronomy Journal, 43, 341-342.

Sotherton, N.W., Boatman, N.D. & Rands, M.R.W. (1989) The ‘conservation headland’ experiment in cereal ecosystems. The Entomologist, 108, 135-143.

Taylor, J.C. & Rudman, J.E. (1966) The distribution of herbage at different heights in ‘grazed’ and ‘dung patch’ areas of a sward under two methods of grazing management. The Journal of Agricultural Science, 66, 29-39.

Thomas, M.B., Wratten, S.D. & Sotherton, N.W. (1991) Creation of ‘island’ habitats in farmland to manipulate populations of beneficial arthropods: Predator densities and emigration. Journal of Applied Ecology, 28, 906-917.

Ideas for doing ecology during the lockdown

If you are a follower of my blog then you will know that I have a thing about roundabouts; if not then follow this link and read about the wonderful world of the famous Bracknell roundabouts 🙂 Seriously though, I, or more correctly, a bunch of my students with the occasional visit from me, spent twelve years sampling roundabouts for a variety of plant and animal life, ranging from bugs through to birds with beetles in between.

I originally set the project up as a pedagogical exercise to make island biogeography and nature reserve design more relevant to UK-based undergraduates. I have a bit of a thing about students swanning off to warm tropical places to do conservation, when we have plenty of our own nature that needs attention much closer to home.

Having come up with the idea of getting students (initially undergraduates, but soon involving a horde of MSc students and even a PhD student) to test the species-area relationship using roundabouts as islands – green oases surrounded by a sea of tarmac,  I had to do something about it, especially as the Borough Council, to my total amazement, agreed that I could do it 🙂

So the project was born and lived on for twelve very productive and enjoyable years. We used pitfall trapping, sweep netting, tree beating, suction sampling, transect sampling for the butterflies and bumblebees and also bird counts.  We sampled the vegetation, measured NOx and recorded how often the grass was mown.  We also measured how far away the nearest green spaces were and the immediate and not so immediate land-use.

To my initial surprise (although perhaps I shouldn’t have been), it turned out that the roundabouts were full of wildlife and behaved like geographical islands, big ones having more species than smaller ones (species-area) and more individuals of those species (area-abundance theory).  We also showed that native plants supported more insects than non-native plants and that this was good for the birds.

Quite a bit of the work is now published although we still have a pile of plant and woodlouse data to write up.

So, how does this relate to our current lockdown status?  You can’t very well go out and sample roundabouts or roadside verges, the police will move you along pretty quickly.  Most of you however, probably have a garden and know people with gardens.  Why not get together (virtually of course) and decide what you want to sample; pitfall traps are probably the easiest thing to start with or you could do a bit of bush and tree beating.  Measure your respective islands (gardens) and start collecting and counting. Then collate your data and see what you turn up. Kevin Gaston and Ken Thompson both formerly at Sheffield University found all sorts of exciting things in Sheffield domestic gardens and if you want a good read about the wildlife of suburban gardens I can recommend Jennifer Owens’ little book https://www.amazon.co.uk/Ecology-Garden-First-Fifteen-Years/dp/0521018412

So, find a trowel and get those plastic/paper party cups, jam jars, or tin cans deployed, or get a broom handle and bed sheet and start being cruel to the trees and bushes and enjoy a bit of outdoor time 🙂

 

 

 

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.

 

*

Just to remind you that I am a champion procrastinator 🙂

 

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.

 

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

 

 

What use are bedbugs?

As an entomologist, I have, over the years, become used to being asked by non-entomologists “What use are wasps?” My wife and mother-in-law being frequent interrogators. What they actually mean is “What use are Vespids?”, in particular what the Americans call yellow jackets, and their ilk.

Not a bed bug – The European wasp Vespula germanica https://en.wikipedia.org/wiki/Yellow_jacket#/media/File:European_wasp_white_bg.jpg

I now have a well-polished response where I explain that wasps are beneficial insects keeping the caterpillars that eat their garden plants under control and that the occasional hole they make in my interlocutor’s soft fruit is just payment for the job they are doing. I am not saying that this answer always satisfies them, especially if their plums have been devastated, but at least they agree that there is some justification for their existence.

Unfortunately I now have a new question to answer. Last summer (2015) my wife and I took our usual holiday to France. We put our car on the Brittany Ferry, m/V Mont St Michel, and after a drink in the bar retired to our cabin, 9108 in case you want to avoid it, me in Bunk A my wife in Bunk B.

Sailing in comfort?

The next morning my wife was not a happy lady and the question I now have to answer is “What use are bedbugs?”!

The bed bug culprit, Cimex lectularius and victim

I have in the past made a convincing case (well I think so) for the usefulness of mosquitoes compared with pandas, but I suspected that making a case for the usefulness of bed bugs that would satisfy my wife, might be more difficult.

Even the Encyclopaedia of Life has nothing good to say about bed bugs. For evolutionary biologists, ecologists and entomologists, bed bugs are very useful in allowing us to relate horror stories about non-conventional sex. Male bed bugs favour a very robust approach to reproduction, as they indulge in what is somewhat coyly termed ‘traumatic insemination (Reinhardt & Siva-Jothy, 2007). Basically they don’t bother with the female genital opening, they mount the female and search for a pouch (Organ of Ribaga or ectospermalage) on the underside of the female (they have been known to mount other males) which they pierce with their intromittent organ (penis) and into which they release their sperm. The spermatozoa then migrate through the body of the female to the oviduct, taking from 2-10 hours to do so (Cragg, 1920). Apparently males never use the genital tract for insemination (Reinhardt & Siva-Jothy, (2007). This somewhat unconventional approach to mating has, as you might expect, harmful effects on the female, with life spans being reduced by about 30% or even causing death (Morrow & Anrnqvist, 2003), multiple matings can be particularly damaging (Mellanby, 1939).

For their human hosts, bed bugs can have a number of unpleasant effects (Reinhardt & Siva-Jothy, 2007), ranging from psychological distress, allergic reactions as in the case of my wife, secondary infections and economic costs, especially if you are an hotelier. All in all, not a very promising candidate for being useful to us humans 🙂 I was beginning to feel that bed bugs had no redeeming features and that if there was a coordinated campaign calling for the destruction of the entire species, I would be unable to defend them. Then a former student came to their rescue. In desperation, I had emailed Mike Siva-Jothy at Sheffield University who has worked on bed bugs since the late 1990s. He passed my email on to Sophie Evison (a former MSc student of mine) and she came to their rescue as follows

“I’ve had a think about this, and I think there are two approaches: 1. dazzle them with the traumatic insemination story or 2. Forensics. I’ve not looked into it, but I’m pretty sure a situation could arise where the contents of a bedbug could drop someone in it, or even perhaps prove an alibi! Do you think your wife would accept that as reasonable?”

I was pretty certain that my wife would not be happy with option 1, but felt that option 2 was definitely worth following up. I very quickly found a paper (Szalanski et al, 2006) in which the possibility of testing the DNA of the blood found in bed bugs was suggested as having a possible forensic application. According to Wikipedia (well if it is good enough for my students) there has already been some success in real life using this very approach. I was now pretty confident that I had found an answer to the question posed by my wife. To be fair, I tested both of them out on her. As predicted, she did not buy the evolutionary biology aspect of the traumatic insemination story as being of any use, but as a great fan of the CSI and NCIS TV shows, she has grudgingly accepted that there is indeed a use for bed bugs! I just hope that all the bed bugs out there appreciate all the effort I have gone to on their behalf 🙂 If anyone else has further suggestions please let me know.

References

Cragg, F.W. (1920) Further observations on the reproductive system of Cimex, with special reference to the behaviour of the spermatozoa. Indian Journal of Medical Research, 8, 32-79

Mellanby, K. (1939) Fertilization and egg production in the bed-bug Cimex lectularius L. Parasitology, 31, 193-199

Morrow, E.H. & Arnqvist, G. (2003) Costly traumatic insemination and female counter-adaptation in bed bugs. Proceedings of the Royal Society of London Series B, 270, 2377-2381

Reinhardt, K. & Siva-Jothy, M. (2007) Biology of the bed bugs (Cimicidae). Annual Review of Entomology, 52, 351-374

Szalanski, A.L., J.W. Austin, J.A. McKern, C.D. Steelman, D.M. Miller, and R.E. Gold. 2006. Isolation and characterization of human DNA from bed bug, Cimex lectularius L., (Hemiptera: Cimicidae) blood meals. Journal of Agricultural and Urban Entomology, 23, 189-194.

 

 

Living inside your grandmother – the wonderful world of aphids

How many of you realise that when you look at an aphid you are simultaneously looking at first, a clonal organism and secondly a mother, her daughter and her granddaughters, all housed in the same body?  This is the wondrous phenomenon known as telescoping of generations.  Aphids, except just before overwintering, give birth to live young (viviparity), and without the need of a male (asexual reproduction/parthenogenesis).  Thus for most of the time when you look at an aphid, you are looking at one member of a clone i.e her sister-self-daughter.  Not only that, but you are looking at not only the aphid in front of your eyes, but at her daughters and her daughter’s daughters, all of which are neatly lined up in tidy rows within the ovarioles of their respective mothers.  With aphids, it is not just maternal effects you have to consider, but also grand-maternal effects, so any experiments should take into account the host-plant and environmental conditions that the ‘grand-mother’ experienced, not just those of the ‘mother’.

Reproduced from Dixon (1973)

In addition, as the eggs are hatched within the aphids before they are born, their total development time, compared with those insects that lay eggs which hatch externally to their mothers, is significantly reduced, thus giving them a head-start in the population development race.  This is suggested as one of the reasons why aphids are so successful as pest insects.

Generally speaking, this wonderful world of internal generations is hidden from us, unless we cruelly dissect the clone mother and extract her ovarioles.  In some aphids however, such as the small willow aphid, Aphis farinosa, where the offspring are a completely different colour from their mother, the next generation of aphids becomes clearly visible without the need to cut open the mother.

And before you ask, as far as I know, there is no evidence that the generations within a generation go on ad infinitum, like a hall of mirrors, although it would be really cool if they did.

No wonder I love aphids so much.

Dixon A.F.G. (1973)  The Biology of Aphids, Edward Arnold, London

P.S. Tony Dixon’s little Biology of Aphids book is a great introduction to the subject, unfortunately out of print, but the good news is that it is still possible to buy second-hand copies for less than £5. Another great and very readable book, is Aphid Ecology, also by Tony and again out of print, except as an e-book.  The really bad news is that the cheapest copy I have been able to find is priced at £43.31 prior to shipping, so if you want to read it the best option is to borrow it from the library.

Magic roundabouts – not just traffic calming devices

Roundabouts or traffic circles as they are known in some parts of the world, are a common feature of modern life.  They can range greatly in size; some are big enough to house small communities such as the Shepherd & Flock roundabout on the outskirts of Farnham, Surrey, which has it’s own pub,

whilst others are simple grass covered circles, such as the one shown below on the outskirts of Bracknell, Berkshire.  Others, even if lacking pubs, may have a mixture of different plants present, some even with mature trees on them, such as the Sports Centre roundabout also in Bracknell.

  

Traditionally, roundabouts have been thought of as simple devices to regulate the flow of traffic and were usually circular raised areas of tarmac, stone, concrete or brick.  More recently however, town and city councils began to add plants and/or artwork.   Some of my favourites in this latter category are found in southern France as shown below or in the title picture of my blog site.

Ecologically speaking however, roundabouts are even more interesting.  For almost fifteen years, I and a number of my students, from undergraduate to post-graduate, have been investigating the ecology of roundabouts and other green spaces in the town of Bracknell, Berkshire.  What started as a purely pedagogic exercise (Leather & Helden, 2005a), turned into a voyage of discovery and a realisation that roundabouts are, and can be, great sources of biodiversity (Helden & Leather, 2004), and in addition, could perhaps act as nature reserves (Leather & Helden, 2005b).  With close attention to mowing regimes (Helden & Leather, 2004) and increasing the proportion of native trees and other plants on them, it is not only insect diversity that is enhanced, but birds also (Helden et al., 2012).

We have found that roundabouts behave very similarly to biogeographical islands, i.e. the bigger they are and the more diverse the habitats present, the more diverse and interesting the fauna that can be found on them.  For example, we found the rare and endangered bug (Hemiptera) Gonocerus acuteangulatus, alive and well on one of the roundabouts and amusingly, another species, Athysanus argentarius, usually found in coastal locations.  Perhaps the salt from winter gritting operations fooled it.

Roundabouts may not be the equivalent of tropical forests but, they and other urban features such as suburban gardens, as demonstrated by Kevin Gaston and colleagues in a series of ground-breaking papers arising from the BUGS project http://www.bugs.group.shef.ac.uk/ in Sheffield and Jennifer Owen in her 30-year study of her Leicester garden (Owen, 2010), are immensely valuable tools for enhancing and conserving biodiversity in our increasingly impoverished world. We have much more to report, from bees, to butterflies and even woodlice.   Watch this space for future instalments.

Helden, A. J. & Leather, S. R. (2004). Biodiversity on urban roundabouts – Hemiptera, management and the species-area relationship. Basic and Applied Ecology 5: 367-377. https://www.harper-adams.ac.uk/staff/profile/files/uploaded/Helden & Leather2004.pdf

Helden, A. J., Stamp, G. C. & Leather, S. R. (2012). Urban biodiversity: comparison of insect assemblages on native and non-native trees.  Urban Ecosystems 15: 611-624. https://www.harper-adams.ac.uk/staff/profile/files/uploaded/Helden_et_al_2012.pdf

Leather, S. R. & Helden, A. J. (2005a). Magic roundabouts?  Teaching conservation in schools and universities. Journal of Biological Education 39: 102-107. http://www.harper-adams.ac.uk/staff/profile/files/uploaded/Leather_&_Helden_JBE_2005.pdf

Leather, S. R. & Helden, A. J. (2005). Roundabouts: our neglected nature reserves? Biologist 52: 102-106. http://www.harper-adams.ac.uk/staff/profile/files/uploaded/Leather_&_Helden_Biologist_2005.pdf

Owen, J. (2010 ) Wildlife of a Garden: A Thirty Year Study,  Royal Horticultural Society, London