Tag Archives: Hemiptera

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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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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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.

Wasp

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.

Bedbug2

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?”!

Bedbug3

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.

 

 

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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’.

aphid telescoping generations

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.

Aphis farinosa

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.

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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,

Shepherd & Flock Farnham

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.

Simple roundabout   Diverse roundabout

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.

DSCF1038DSCF1036

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.

Gonocerus acuteangulatus

Athysanus

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

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