Tag Archives: Lepidoptera

Butterflies Galore – visual treats from two very different books

BG1

I have written a lot of book reviews over the last thirty years or so; initially for mainstream scientific journals; those were the days when journal editors had never heard of impact factors and space was specifically set aside for such articles. And latterly, for the in-house member’s bulletins of learned societies such as Antenna; the excellent and very glossy publication of the Royal Entomological Society.  Book reviews are generally a bit of a chore, especially if the book in question is an edited volume, but busy academics can sometimes be persuaded to take a review on if they think that the book (the only payment you receive is a free copy) will justify the effort.  Occasionally one gets the chance, or feels the urge, to use a book review as a means of getting a particular message across to a wider audience.  I once managed to have one of my ‘on the importance of entomology’ rants published in Trends in Ecology & Evolution (Leather, 2008) using this route.  Up until now however, unless you count my somewhat tongue-in-cheek review of Anna Aphid, I have not used my blog in this way.   This is, however, about to change.

At the end of November last year (2015), I received an email from Caroline Young of Firefly Books who wondered if I would like to review a new entry to their catalogue, Butterflies, by Ronald Orenstein and Thomas Marent.   It was such a flattering email that I succumbed to her blandishments, hence this first official book review on my site.  To retain some scientific integrity however, I decided that I would do a comparative review.  Fortuitously, it just so happened, that I had to hand another book about butterflies; one that I had semi-promised to review for the Royal Entomological Society (Howse, 2014), but until now, had never got around to doing.  In one fell swoop I was thus able to salve my conscience and do two favours 🙂

When reviewing a book I have a little mental list of questions that I answer as I read it.

  1. Would I buy it?
  2. Would I recommend a colleague to buy it?
  3. Would I recommend it to students as worth buying?
  4. Would I ask the library to buy it?
  5. Would I recommend it to anyone to buy it?

All these have the same subsidiary questions attached to them; If not why not, if yes, why?

First, Butterflies, billed by the publisher’s blurb as a “visual feast that showcases the beauty and mystery of butterfly and moth species from around the globe”.  A good place to start with a book review is with a summary of the contents and the aim(s) of the author(s).  There are eleven named chapters in total, with a thirty page introductory chapter, aptly titled Introducing butterflies.  This chapter, which like all the others, is beautifully illustrated with stunning photographs, briefly covers the main features of butterfly biology and ecology, from evolution, taxonomy, flight, mimicry, courtship, oviposition, development, feeding, predation, migration and concludes with climate change and conservation.  There is no overall ‘mission statement’ per se, but towards the end of the introduction the authors write “We need to know more and to do better. In many parts of the world, butterflies are disappearing at a rapid rate.  We need to understand what is happening to them, and why, if we are to stop or reverse their decline.  We need to create space for butterflies.”

From this I take it that the purpose of the book is to inspire adult non-entomologists to take an interest in butterflies in general and to create habitats for them in their gardens. I also think that there other aim is to inspire the younger generation to become involved with butterfly conservation either professionally or as an extra-mural interest.  The twelve chapters that follow the introductory piece are first, taxonomically based, e.g. Swallowtails, Skippers, Whites and then to do with their biology and ecology, covering topics such as wings, life history, diet, mimicry etc.  The last chapter is about those too-often overlooked Lepidoptera, the moths.  Each chapter is dominated by the beautiful photographs, each of which is accompanied by a succinct pen sketch giving a brief description of the species shown and some useful nuggets of information about the distribution, taxonomic position of the species and something about their biology.  Some of these nuggets were new to me, perhaps not surprisingly, as I am not primarily a lepidopterist 🙂

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I was, for example, interested and intrigued by the suggestion that eggs of The Map, Araschnia levana are mimics of the flowers  of its larval host plant, nettle (Urtica spp.).

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http://bioweb.uwlax.edu/bio203/2011/homolka_kail/reproduction.htm   ttps://commons.wikimedia.org/wiki/File:Urtica_dioica.JPG

In fact I was so intrigued that I felt the need to test it out by searching for photographs of nettle flowers. These shown are the closest I could find that come close to matching the eggs and so to a certain extent I remain unconvinced.  I will however, leave that up to you to decide for yourselves.

In summary, this book is as advertised, “a visual feast that showcases the beauty and mystery of butterfly and moth species from around the globe.”  It is not a text-book, nor is it an exhaustive pictorial catalogue, you could not use it as an identification guide. It does however, give a good and accessible overview of some basic butterfly biology and ecology and also great factoids to store away for use at an opportune moment.  So the bottom line:

  1. Would I buy it?   – No, in my opinion, it does not contain enough entomological detail for me as a professional to justify the $45 price tag.
  2. Would I recommend a colleague to buy it? Probably not for the same reason as above.
  3. Would I recommend it to students as worth buying? Again, probably not, but I might suggest that they put it on their Christmas or birthday lists.
  4. Would I ask the library to buy it? Yes, I think that it contains enough useful information to make it attractive to a non-specialist student reader interested in an easy to understand book with enough useful essay material in it.

and finally, would I recommend it to anyone else to buy it,? Yes it is a nice book, albeit of the coffee table variety, but in my opinion at the upper end of that market and anything that might spark an interest in entomology amongst the as yet unconverted, can only be a good thing.

And now, Philip Howse’s book, Seeing Butterflies, which is subtitled, New Perspectives on Colour, Patterns and Mimicry.  The publisher’s blurb in this instance states “See living butterflies and moths through new eyes through Philip Howse’s fascinating text and superb imagery….This new way of looking at these beautiful and iconic images will inform and inspire nature-lovers, photographers artists and scientists.”  Some major claims are being made here, implying that this is a serious book aimed at specialists, yet with the potential to appeal to a much wider readership.  Does it live up to these claims?

As with Butterflies, we are presented with twelve beautifully illustrated chapters.  Here though, with a chapter entitled, Seeing: Illusion, deceit and survival, we know from the start that this book is about vision, about visibility and invisibility and about optical illusions.  Chapter two continues this theme, being about defence and illusion while Chapter three examines the evolution of butterflies and mimicry.  The remaining chapters, as with Butterflies, are taxonomically based and examine the very varied visual defence mechanisms exhibited across the various butterfly families.  The photographs may not be as professional, as many or as stunning as those in Butterflies, but the science is much stronger, yet still very accessible to the lay reader.  There is also much more natural history, although again, this is not a book that would be useful for identification purposes.  On the other hand there are some marvellous nuggets and factoids, with which to regale friends, students and anyone else that you can catch.   One that sticks in my mind particularly, is that apparently the small tortoiseshell, Aglais urticae was once known as the ‘devil butterfly’ in Scotland. Philip speculates that this might be because it “comes out of the darkness of winter and hibernation, marked in red and black”.  As with Butterflies there were numerous factoids that intrigued and interested me.  In particular Philip’s claims for the eyed hawkmoth, Smerinthus ocellata, that he feels can impersonate a bracket fungus, a pile of dead leaves and a fox-like animal!

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The first two I am quite happy about, but the third suggestion seems to need quite a stretch of the imagination 🙂

There is more of the author apparent in Seeing Butterflies than in Butterflies; Philip recalls childhood memories, and other personal experiences to illustrate the points that he makes and this gives the book a very user-friendly feel that is, to a certain extent, lacking in Butterflies. I also think that on the whole, the book manages to live up the somewhat over-hyped blurb.

And so the bottom line:

  1. Would I buy it? – Yes I would, very nicely priced, well-written and enough science to keep me happy and interested.
  2. Would I recommend a colleague to buy it? Yes, even a non-entomological colleague would be likely to find it worth the money.
  3. Would I recommend it to students as worth buying? Yes, I would certainly suggest it to my PhD students and MSc Entomology students, but probably not to undergraduates although I would definitely suggest that they put it on their Christmas and/or birthday lists.
  4. Would I ask the library to buy it? Yes, both as a recommended book for the entomologists and it contains enough useful information to make it attractive to a non-specialist student reader interested in an easy to understand book with useful essay material in it.

 and finally, would I recommend it to anyone else to buy it,? Yes it is a nice book and should appeal to anyone who has a genuine interest in the natural world.

 So there you have it, my first official ‘blog’ book review. There may be more to come, not necessarily commissioned ones, but just books that take my fancy, but if there are any publishers, or authors out there who think that I might like to review one of their books, feel free to contact me to discuss it.

 

References

Howse, P. (2014) Seeing Butterflies, Papdakis Publisher, Winterbourne, UK.  Paperback, 176 pp, £16.99 ISBN-13: 978-1-906506-46-9

Leather, S.R. (2008). Conservation entomology in crisis. Trends in Ecology & Evolution, 123, 184-185

Orenstein, R. & Marent, T. (2015) Butterflies, Firefly Books, Buffalo, USA. Hardback, 288 pp, $45 ISBN-13: 978-1-77085-580-0; ISBN-10: 1-77085-580-7

 

Postscript

For anyone seriously interested in writing academic book reviews I can recommend this site by Dr Perpetua Turner https://peptalkecology.wordpress.com/2016/01/13/writing-an-academic-book-review/

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Insect egg mimics – plant parts that pretend to be insect eggs

Back in the 1980s I was a forest entomologist working for the UK Forestry Commission at their Northern Research Station based just outside Edinburgh.  I was working on two important pests of Lodgepole pine (Pinus contorta), the pine beauty moth, Panolis flammea and the European pine sawfly, Neodiprion sertifer.  The pine beauty moth lays its eggs in short rows on the upper surface of pine needles in late spring/early summer.

Panolis eggs

Eggs of the pine beauty moth, Panolis flammea  (Image courtesy of Stanislaw Kinelski, Bugwood.org http://www.invasive.org/browse/detail.cfm?imgnum=1258002).

They are pale yellow when first laid and gradually darken as they mature becoming a deep violet colour just before they hatch.  The eggs of Neodiprion sertifer are also laid on the upper part of the pine needles, but are ‘injected’ just under the cuticle of the needle.  After a few days a small necrotic patch develops at the oviposition site.

Neodiprion eggs

Eggs of the European pine sawfly, Neodiprion sertifer (image courtesy of A. Steven Munson, USDA Forest Service, Bugwood.org http://www.forestryimages.org/browse/detail.cfm?imgnum=1470178)

Spring field work for me was several days of rather tedious egg counting and as I scrutinised hundreds of pine needles, I noticed that some of the needles had little flecks or balls of resin on them,

Resin flecks

Resin flecks on bristlecone pine, Pinus arsitata – often confused with scale insect infestations (Photo by Hans G. Oberlack via Wikipedia).

which were, especially on gloomy days in the depths of the forest, quite easy to confuse with pine beauty moth eggs.  Other needles had discoloured areas that looked like pine sawfly eggs or also a bit like pine beauty moth eggs, depending on how they were arranged.

Egg mimics

Possible insect egg mimics on pine needles

Long days working alone in a forest allow one the time to think and it occurred to me one day that if I was being fooled by these ‘pseudo eggs’ then perhaps egg-laying pine beauty moths and pine sawflies might also be getting confused and avoiding laying eggs on these apparently already infested needles.   I wondered if there was any evidence to support my far-fetched hypothesis and to my delight found a paper by (Williams & Gilbert, 1981) that demonstrated quite convincingly that passion-fruit vines, produce structures resembling eggs of Heliconius butterflies and that these deter them from laying eggs on them.

Egg mimics 2

Egg mimics on passion flower leaf – Photo by Lawrence Gilbert http://plantmimicrybz2820.blogspot.co.uk/2015/04/the-passiflora-genus.html

I also found papers that showed that other Lepidoptera (Rothschild & Schoonhoven, 1977; Nomakuchi et al., 2001) and beetles (Mappes & Mäkelä, 1993), are able to discriminate between leaves that already have eggs laid on them and avoid laying more eggs on those leaves, thus reducing larval completion.

Although I never formally checked it, I got the impression that needles bearing ‘egg mimics’ had fewer pine beauty moth eggs or pine sawfly eggs laid on them than those without.  Another question that could be easily looked at is whether pine trees in areas that have had outbreaks have more speckled needles than those in non-outbreak areas.  I always meant to do some formal sampling and a proper experiment to back up my feelings, but never found the time to do it.  I am pretty certain that I am unlikely to get round to doing this in the near future (if ever), but I would like to know if this is indeed another example of  a plant mimicking insect eggs.  I would be very happy indeed if any of you feel like testing my hypothesis and look forward to seeing the results in print.

 

References

MacDougal, J.M. (2003)  Passiflora boenderi (Passifloraceae): a new egg mimic passionflower from Costa Rica.  Novon, 13, 454-458

Mappes. J. & Mäkelä, I. (1993)  Egg and larval load assessment and its influence on oviposition behaviour of the leaf beetle Galerucella nymphaeae.  Oecologia, 93, 38-41

Nomakuchi, S., Masumoto, T., Sawada, K., Sunahra, T., Itakura, N. & Suzuki, N. (2001) Possible Age-Dependent Variation in Egg-Loaded Host Selectivity of the Pierid Butterfly, Anthocharis scolymus (Lepidoptera: Pieridae): A Field Observation .  Journal of Insect Behavior, 14, 451-458.

Rothschild, M. & Schoonhoven, L.M. (1977) Assessment of egg load by Pieris brassicae (Lepidoptera: Pieridae). Nature, 266, 352-355.

Williams, K.S. & Gilbert, L.E. (1981) Insects as selective agents on plant vegetative morphology: egg mimicry reduces egg laying by butterflies. Science, 212, 467-469.

 

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Ten Papers that Shook My World – Haukioja & Niemelä (1976) – the plant “immune response”

To me this is a landmark paper, both personally and for ecology in general.   I first came across it in the second year of my PhD at the University of East Anglia (1978) and given where it was published, would probably never have seen it if my supervisor, Tony Dixon, hadn’t had a collaborative link with Erkki Haukioja of Turku University (Finland).

That individual plants of the same species are more or less susceptible (constitutive or innate resistance) to pests and diseases has been known for a very long time (e.g. Painter, 1958; Beck, 1965) and has been exploited by plant breeders as part of many pest management programmes.  Despite the stunning footage of the questing bramble in David Attenborough’s classic documentary The Private Life of Plants, plants are often thought of as passive organisms.  The idea that plants might actually respond directly and quickly to insect attack was more in the realms of science fiction than science fact, but this all changed in the 1970s. In 1972 a short paper in Science (Green & Ryan, 1972) suggested that plants might not be as passive as previously thought. Green & Ryan working in the laboratory with the Colorado Potato Beetle, Leptinotarsus decemlineata, showed that when tomato leaves were damaged by beetle feeding the levels of a proteinase inhibitor were raised not just in the wounded leaves but in nearby leaves as well. As proteinase inhibitors were well-known to be part of the plant defence system, they hypothesised that this was a direct response of the plant to repel attack by pests and that it might be a useful tool in developing new pest management approaches. So what does this have to do with two Finnish entomologists?

Erkki Haukioja and his long-term collaborator, Pekka Niemelä were working on an important lepidopteran defoliator of birch, in the far north of Finland, at the Kevo Subarctic Research Station.Kevo

http://www.eu-interact.org/field-sites/finland-4/kevo/

The defoliator that they were working on was the autumnal moth, now Epirrita autumnata, but then Oporinia autumnata.

Epirrita

http://ukmoths.org.uk/show.php?bf=1797

The autumnal moth, as with many tree-feeding Lepidoptera, has a 7-10 year population cycle (Ruohmäki et al., 2000).

Population cycles

Natural enemies are often cited as the causes of these cycles (Turchin et al., 1999) although other factors such as weather (Myers, 1998) or even sunspot activity (Ruohmäki et al., 2000)

Sunspot

have also been suggested. It had also been suggested that the marked population cycles of the larch bud moth, Zeiraphere diniana were caused by changes in the susceptibility of their host trees after defoliation (Benz, 1974). In 1975, Haukioja and his colleague Hakala, attempting to explain the cyclical nature of the E. autumnata population cycles wondered if they were being driven by the insects themselves causing changes in the levels of chemical defence in the trees. To test this Erkki and Pekka did two neat field experiments, remember Green & Ryan’s work was laboratory based and did not test the effects seen on the insects. They first fed Epirrita larvae on foliage from previously defoliated and undefoliated birch trees and found that the pupae that developed from those larvae fed on previously defoliated trees were lighter than those that had fed on previously undefoliated trees (Hauikioja & Niemelä, 1976). At the same time they also did an experiment where they damaged leaves but then rather than feeding the larvae on those leaves, fed them on nearby adjacent undamaged leaves and compared them with larvae feeding on leaves from trees where no damage had occurred. Those larvae feeding on undamaged leaves adjacent to damaged leaves grew significantly more slowly than those feeding on leaves that came from totally undamaged trees (Haukioja & Niemelä, 1977). So pretty convincing evidence that the trees were responding directly to insect damage and altering their chemistry to become more resistant, i.e. an induced defence and not a constitutive one.

Their results had a major impact on the field. The great and the good from around the world found it a fascinating subject area and a plethora of papers investigating the effects of insect feeding on induced defences in birch and willow trees soon followed (e.g. Fowler & Lawton, 1984a; Rhoades, 1985; Hartley & Lawton, 1987) and not forgetting the original researchers (e.g. Haukioja & Hahnimäki, 1984). I, with the aid of colleagues, also added my ‘two pennorth’ (I did say the idea shook my world) by extending the concept to conifers (Leather et al., 1987; Trewhella et al., 1997). The terms rapid induced resistance and delayed induced resistance soon entered the language, the first to describe those changes that occurred within minutes of feeding damage and the second, those that did not take effect until the following year (Haukioja & Hahnmäki, 1984; Ruohmäki et al., 1992) Such was the interest generated by the topic that by 1989 there were enough studies for a major review to be published (Karban & Myers, 1989).

Controversy reared its ugly head early on when Doug Rhoades suggested that not only did plants resist insect attack actively but that they could talk to each other and warn their neighbours that the ‘bad guys’ were in the neighbourhood (Rhoades, 1983, 1985). This sparked a brief but lively debate (e.g. Fowler & Lawton, 1984b, 1985). Ironically it is now taken as axiomatic that plants talk to each other using a range of chemical signals (van Hulten et al., 2006; Heil & Ton, 2008) as well as informing the natural enemies of the pests that a suitable food source is available (e.g. Edwards & Wratten, 1983; Amo et al., 2013; Michereff et al., 2013).

Ton cartoon

A great cartoon from Jurriaan Ton at Sheffield University. https://www.shef.ac.uk/aps/staff-and-students/acadstaff/ton-jurriaan

We now have a greatly increased understanding of the various metabolic pathways that induce these defences against different insect pests (e.g. Smith & Boyko, 2007) and can, by genetically manipulating levels of compounds such as jasmonic and salicyclic acids or even applying them directly to plants affect herbivorous insect communities and their natural enemies thus improving crop protection (e.g. Thaler, 1999; Cao et al., 2014; Mäntyllä, 2014). No wonder this was an idea that shook my world, and yours.

 

Post script

The study of induced plant defences or resistance is now dominated by molecular biologists and current practice is to use the term priming and not induced defence. The increased understanding that this new generation has brought to the field is undeniable but I always feel it is a great shame that they seem to have forgotten those early pioneers in the field.

 

References

Amo, L., Jansen, J.J., Van Dam, N.M., Dicke, M., & Visser, M.E. (2013) Birds exploit herbivore-induced plant volatiles to locate herbivorous prey. Ecology Letters, 16: 1348-1355.

Baldwin, I.T. & Schultz, J.C. (1983) Rapid changes in tree leaf chemistry, induced by damage: evidence for communication between plants. Science, 221, 277-279.

Beck, S.D. (1965) Resistance of plants to insects. Annual Review of Entomology, 10, 207-232.

Benz, G. (1974). Negative Ruckkoppelung durch Raum-und Nahrungskonkurrenz sowie zyklische Veranderung. Zeitschrift für Angewandte Enomologie, 76: 196-228.

Cao, H.H., Wang, S.H., & Liu, T.X. (2014) Jasomante- and salicylate-induced defenses in wheat affect host preference and probing behavior but not performance of the grain aphid, Sitobion avenae. Insect Science, 21, 47-55.

Edwards, P.J. & Wratten, S.D. (1983) Wound induced defences in plants and their consequences for patterns of insect grazing. Oecologia, 59: 88-93.

Fowler, S.V. & Lawton, J.H. (1984a) Foliage preferences of birch herbivores: a field manipulation experiment. Oikos, 42: 239-248.

Fowler, S.V. & Lawton, J.H. (1984b) Trees don’t talk : do they even murmur? Antenna, 8: 69-71.

Fowler, S.V. & Lawton, J.H. (1985) Rapidly induced defences and talking trees: the devils’ advocate position. American Naturalist, 126: 181-195.

Green, T.R. & Ryan, C.A. (1972) Wound induced proteinase inhibitor in plant leaves: a possible defense mechanism against insects. Science: 175: 776-777.

Hartley, S.E. & Lawton, J.H. (1987) Effects of different types of damage on the chemistry of birch foliage and the responses of birch feeding insects. Oecologia, 74: 432-437.

Haukioja, E. & Hakala, T. (1975) Herbivore cycles and periodic outbreaks. Report of the Kevo Subarctic Research Station, 12: 1-9

Haukioja, E. & Hanhimäki, S. (1984) Rapid wound induced resistance in white birch (Betula pubescens) foliage to the geometrid Epirrita autumnata: a comparison of trees and moths within and outside the outbreak range of the moth. Oecologia, 65, 223-228.

Haukioja, E. & Niemelä, P. (1976). Does birch defend itself actively against herbivores? Report of the Kevo Subarctic Research Station 13: 44-47.

Haukioja, E. & Niemelä, P. (1977). Retarded growth of a geometrid larva after mechanical damage to leaves of its host tree. Annales Zoologici Fennici 14: 48-52.

Heil, M. & Ton, J. (2008) Long-distance signalling in plant defence. Trends in Plant Science, 13: 264-272.

Karban, R. & Myers, J.H. (1989) Induced plant responses to herbivory. Annual Review of Ecology & Systematics, 20: 331-348.

Leather, S.R., D., W.A., & Forrest, G.I. (1987) Insect-induced chemical changes in young lodgepole pine (Pinus contorta): the effect of previous defoliation on oviposition, growth and survival of the pine beauty moth, Panolis flammea. Ecological Entomology, 12: 275-281.

Mäntyllä, E., Blande, J.D., & Klemola, T. (2014) Does application of methyl jasmonate to birch mimic herbivory and attract insectivorous birds in nature? Arthropod-Plant Interactions, 8, 143-153.

Michereff, M.F.F., Borges, M., Laumann, R.A., Dinitz, I.R., & Blassioli-Moraes, M.C. (2013) Influence of volatile compounds from herbivore-damaged soybean plants on searching behavior of the egg parasitoid Telonomus podisi. Entomologia experimentalis et applicata, 147: 9-17.

Trewhella, K.E., Leather, S.R., & Day, K.R. (1997) Insect induced resistance in lodgepole pine: effects on two pine feeding insects. Journal of Applied Entomology, 121: 129-136.

Myers, J. H. (1998). Synchrony in outbreaks of forest lepidoptera: a possible example of the Moran effect. Ecology 79: 1111-1117.

Painter, R.H. (1958) Resistance of plants to insects. Annual Review of Entomology, 3: 267-290.

Rhoades, D.F. (1983) Responses of alder and willow to attack by tent caterpillar and webworms: evidence for pheromonal sensitivity of willows. American Chemical Society Symposium Series, 208: 55-68.

Rhoades, D.F. (1985) Offensive-defensive interactions between herbivores and plants: their relevance in herbivore population dynamics and ecological theory. American Naturalist, 125: 205-238.

Ruohomäki, K., Hanhimäki, S., Haukioja, E., Iso-iivari, L., & Neuvonen, S. (1992) Variability in the efficiency of delayed inducible resistanec in mountain birch. Entomologia experimentalis et applicata, 62: 107-116.

Ruohmäki, K., Tanhuanpää, M., Ayres, M.P., Kaitaniemi, P., Tammaru, T. & Haukioja, E. (2000) Causes of cyclicity of Epirrita autumnata (Lepidoptera, Geometridae): grandiose theory and tedious practice. Population Ecology, 42: 211-223

Smith, C.M. & Boyko, E.V. (2007) The molecular basis of plant resistance and defence responses to aphid feeding: current status. Entomologia experimentalis et applicata, 122: 1-16.

Thaler, J. (1999) Induced resistance in agricultural crops: effects of Jasmonic acid on herbivory and yield in tomato plants. Environmental Entomology, 28, 30-37.

Turchin, P., Taylor, A. D. &Reeve, J. D. (1999). Dynamical role of predators in population cycles of a forest insect: an experimental test. Science 285: 1068-1071.

Van Hulten, M., Pelser, M., van Loon, L.C., Pieterse, C.M.J. & Ton, J. (2006) Costs and benefits of priming for defense in Arabidopsis. Proceedings of the National Academy of Sciences USA, 103: 5602-5607.

 

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Entomological classics – The insect olfactometer

In 1924, Norman McIndoo (1881-1956) an entomologist at the Fruit Insect Investigation Department in the USDA Bureau of Entomology based in Washington DC was instructed by his boss Dr. A.L. Quaintance, to make a study of insect repellents and attractants.   After two years of frustrated experimentation McIndoo invented a piece of apparatus that would revolutionise the study of insect behaviour, the Y-tube olfactometer (McIndoo, 1926) . He freely admitted in his paper that he had borrowed the name from the Zwaademaker olfactometer (Zwaademaker, 1889) a device used to test the sense of smell in humans.  As you can see however, his apparatus bore no resemblance to that of Zwaademaker.

Zwaardemaker olfactometer    McIndoo olfactometer

McIndoo ‘s apparatus was first used to find out whether Colorado potato beetles (Leptinotarsa decemlineata) responded to the odour of the potato plants. The beetles were placed in a dark bottle in a light-tight box, the bottle being attached to the stem of the Y-tube by a tube through which the beetles were able to move, at first being attracted to the light. Once they reached the junction of the Y they then had to make a choice between the two forks this time using their sense of smell. A pump was used to draw air from the two forks, one of which was connected to a jar containing a potato plant, the other which held the control substance. In theory, once at the fork the beetles were confronted with two streams of air, one smelling of potato, the other being odourless. McIndoo was indeed able to show that about 70% of the beetles responded positively to the odour produced by the potatoes. He also showed that the beetles responded to extracts made from the foliage of a number of different host plants.  He briefly mentions in the paper that the beetles were able to tell the opposite sex by smell and that the males would follow sexually mature females. He had accidentally discovered insect sex pheromones but did not realise it at the time. In the last part of his paper he provides data showing that other insect species, including Lepidoptera, were also able to respond to host plant odours.  The Y-tube olfactometer and the closely related T-tube olfactometers soon became the accepted way to test insect response to odours and are widely used in laboratories around the world to this day, for example http://weslaco.tamu.edu/research-programs/entomology/subtropical/behavior/ and http://sciencebykathy.wordpress.com/

Two way olfactometer

http://openi.nlm.nih.gov/detailedresult.php?img=3422343_pone.0043607.g005&req=4

They do however have some limitations; there is a tendency for turbulence to occur at the junction of the Y- and T-tubes which means that there is some mixing of the test odours and this means that there is not a clearly delineated odour field into which the insects can enter, leave and re-enter if they so wish. In 1970, Jan Pettersson from the Swedish University of Agricultural Sciences at Uppsala, invented the four-way olfactometer with which to test the existence of a sex pheromone in the aphid Schizaphis borealis (Pettersson, 1970).

Pettersson 4 way   Pettersson 4 way 1

The four-way olfactometer provides a neutral central zone which is surrounded by four very distinct odour boundaries which the test insects can enter, sample the odour and then either stay or leave and move into another area of the apparatus. Louise Vet and colleagues (Vet et al., 1983) from the University of Leiden added some modifications to the original Pettersson version, with which to study the behaviour of aphids and their parasitoids.

Vet 4 way

 The four-way olfactometer, whether a Pettersson or Vet version, or a modification of the two, is now regarded as the ‘gold’ standard and is used very widely around the world.

Four way - Indian

http://www.nrcb.res.in/gallery8.html

It is certainly our research group’s favoured version and we use it for testing the responses of aphids, hymenopteran parasitoids, lepidoptera and beetles to a range of odours (Trewhella et al., 1997; Leahy et al., 2007; Pope et al., 2012). We are currently using mini-versions to test the olfactory responses of predatory mites. Watch this space.

References

Leahy, M.J.A., Oliver, T.H., & Leather, S.R. (2007) Feeding behaviour of the black pine beetle, Hylastes ater (Coleoptera: Scolytidae). Agricultural and Forest Entomology, 9, 115-124. http://onlinelibrary.wiley.com/doi/10.1111/j.1461-9563.2007.00328.x/full

McIndoo, N.E. (1926) An insect olfactometer. Journal of Economic Entomology, 19, 545-571

Pope, T.W., Girling, R.D., Staley, J.T., Trigodet, B., Wright, D.J., Leather, S.R., Van Emden, H.F., & Poppy, G.M. (2012) Effects of organic and conventional fertilizer treatments on host selection by the aphid parasitoid Diaeretiella rapae. Journal of Applied Entomology, 136, 445-455. http://onlinelibrary.wiley.com/doi/10.1111/j.1439-0418.2011.01667.x/full

Pettersson, J. (1970). An aphid sex attractant I Biological studies. Entomologia Scandinavica 1: 63-73.

Sanford, E.C. (1891) Laboratory course in physiological psychology. American Journal of Psychology, 4, 141-155, http://psychclassics.yorku.ca/Sanford/course2.htm

Trewhella, K.E., Leather, S.R., & Day, K.R. (1997) The effect of constitutive resistance in lodgepole pine (Pinus contorta) and Scots pine (P. sylvestris) on oviposition by three pine feeding herbivores. Bulletin of Entomological Research, 87, 81-88. http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=2497592

Vet, L.E.M., Van Lenteren, J.C., Heymans, M., & Meelis, E. (1983) An airflow olfactometer for measuring olfactory responses of hymenopterous parasitoids and other small insects. Physiological Entomology, 8, 97-106. http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3032.1983.tb00338.x/abstract

Zwaademaker, H. (1889) On measurement of the sense of smell in clinical examination. The Lancet, 133, 1300-1302

 

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Silk- not just a spider thing

Mention silk and most people will, I guess, immediately think of spiders and cobwebs.

Pressed a bit further, some may mention silkworms, and some might even know the word sericulture and that the common silkworm feeds on mulberry bushes.   What they may not know, is that the silk worm is the larvae of the moth Bombyx mori and that there are actually four species of lepidopteran larvae commonly used in silk production.  These are pictured below in the lovely illustration from Meyers Konversations-Lexikon; next to the picture are some B. mori larvae.

Silkworm larvae Silkworms

Meyers Konversations-Lexikon, 4th Auflage, Band 14, Seite 826a (4th ed., Vol. 14, p.826a)

Four of the most important domesticated silk moths. Top to bottom: Bombyx mori, Hyalophora cecropia, Antheraea pernyi, Samia cynthia. From Meyers Konversations-Lexikon (1885-1892

Silk production is of course not just a feature of spiders and lepidoptera.  It is a widespread feature of insect life, being used for pupal cases, as a mode of transport (ballooning) as shown by larvae of the gypsy moth and other species of Lepidoptera,

ballooning gypsy moth            ballooning gypsy moth drawing

protective cases as in larval caddis flies or also, by some caddis fly larvae, as fishing equipment.

 caddisfly_larva  Caddis fly net

But in my opinion, the most dramatic use of silk is that seen in a genus of micro-moths, belonging to the Yponomeutidae, the small ermine moths, Yponomeuta.  They and their relatives, are silk-producers extraordinaire.  Collectively, they are known as small ermine moths; so called because of their adult colouration which resembles the ermine worn by nobility and small, because of the existence of several larger moths with ermine in their names.

Yponomeuta_evonymellus

http://commons.wikimedia.org/wiki/File:Yponomeuta_evonymella-02_(xndr).jpg#file

The larvae are less attractive and are the web/silk producers.

Yponomeuta_evonymella_caterpillars

http://commons.wikimedia.org/wiki/File:Yponomeuta.evonymella.caterpillars.jpg

My particular favourite is the bird cherry ermine moth, and not just because the bird cherry is my favourite tree.  (My eldest son’s middle name is bird cherry, albeit in Finnish). The adult moths lay their eggs in August, in clusters of up to 100 or so on young twigs of the bird cherry Prunus padus, cover them with an egg shield and then die (Leather, 1986).  The eggs hatch shortly afterwards and the larvae spend the winter under the egg shield until the following spring.  When the buds begin to burst in spring, the larvae emerge from beneath the shield and begin to feed gregariously on the newly emerging leaves, spinning a web that protects them from natural enemies  and may also help in thermoregulation and as a trail indicator (Kalkowski, 1958)  http://edepot.wur.nl/201846 .  It is possible to have great fun by selecting a lead larvae to act as a trail blazer and watch the rest of the colony follow them to a destination you have chosen.

Every three to four years or so, populations of the moths get so high that they exhaust their food supplies, defoliating entire trees and covering  them with a tough coating of silky white webbing (Leather, 1986; Leather & Mackenzie, 1994).  In fact, in Finland, I once saw three neighbouring trees totally enveloped in a silken tent caused by the bird cherry ermine moth, Yponomeuta evonymellus, that you could enter and shelter inside from the rain.  Once they really get going as spring progresses, the landscape, particularly if in an area where bird cherry is common, begins to take on a somewhat wintry look, which for May is a little odd.  Those of who you, who have travelled north of Perth in Scotland, on the A9, will be familiar with this phenomenon.  It frequently makes the Scottish newspapers and generates headlines such as “winter wonderland” or “ghostly landscape”. As they run out of trees, the larvae begin to migrate in a desperate search for trees with leaves still on them, and by now, have become less fussy about what they eat.  It is at this wandering stage of their life that the true extent

Yponomeuta webbing  bird cherry emrine moth webbing

of their singlemindedness (I have seen a trail of thousands of larvae marching along a railway line; they didn’t survive the passing of the 0850 from Helsinki) and their ability to produce silk becomes startlingly apparent.

Ermine moths on car    Ermine_moth_larva_on_a_Swedish_army_bike

http://commons.wikimedia.org/wiki/File:Ermine_moth_larva_on_a_Swedish_army_bike.jpg

Truly, silk is not just a spider thing.

Kalkowski, W. (1958). Investigations on territorial orientation during ontogenic development in Hyponomeuta. Folia Biol Krakow 6: 79-102.

Leather, S. R. & Mackenzie, G. A. (1994). Factors affecting the population development of the bird cherry ermine moth, Yponomeuta evonymella L. The Entomologist 113: 86-105.

Leather, S. R. (1986). Insects on bird cherry I The bird cherry ermine moth, Yponomeuta evonymellus(L.). Entomologist’s Gazette 37: 209-213.

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Where have all the woolly bears gone? Woolly bears what are they?

Just a brief thought this week, mainly about shifting baselines and changing perceptions.  I attended the launch of the State of Britain’s Larger Moth’s Report   http://www.mothscount.org/uploads/State%20of%20Britain’s%20Larger%20Moths%202013%20report.pdf last week (February 1st) which as well as giving me the chance to catch up with a number of old friends, also enabled me to hear Chris Packham http://www.chrispackham.co.uk/  giving a lively and very entertaining talk about why moths are important and how he got hooked by ‘natural history’.  He cited as one of the main factors,  his childhood experiences of rearing (or attempting to rear) woolly bear caterpillars, the larvae of the Garden Tiger moth Arctia caja,  a widespread and common species when I was a child and teenager in the 1960s and early 1970s.

Woolly bear larva

http://www.wildlifeinsight.com/Insight/?p=3468

GardenTiger2SF

When I was earning extra money working as a postman in the Vale of York during my student years, it was one of the insects that I could guarantee I would encounter on my round.   Despite its wide range and great abundance, this moth has suffered a huge decline in numbers and I have hardly seen one since I was a long-haired, flares wearing student.  Like Chris Packham, it was the opportunity to interact with such a striking insect, which kept me interested in the natural world despite the competing interests of girls and beer.  As I write, I am teaching on a module (Ecological Entomology) of our MSc Entomology course http://www.harper-adams.ac.uk/postgraduate/201004/entomology (incidentally the only one in the UK).  Having been reminded of the Garden Tiger by Chris Packham, I quickly substituted my population simulation modelling exercise on the Speckled Wood Butterfly, with one on the Garden Tiger.  After I had finished introducing the subject to the students, Kevin, a mature student said that it was collecting and rearing woolly bear caterpillars as a child that had led to him to be sitting in front of me now.  One of the other students, a recent graduate, piped up and asked “what is a woolly bear?  I have never heard of them”.   He was there because he had been inspired by his project supervisor.

I guess the point that I am trying to make, is that whilst Kevin and I were inspired to become entomologists by our childhood experiences, Craig had to wait until he was exposed to the wonder and awe of working with insects as an undergraduate.  So what’s the problem you may ask?  Both students have ended up in my class. There is a problem however; the last BSc in Entomology in the UK stopped running in 1995, there are no Entomology Departments in UK universities , there are as far as I can ascertain, very few academic entomologists who describe themselves as entomologists in their job title e.g. as Professor of Entomology.  As far as I know, there is only me, http://www.harper-adams.ac.uk/staff/profile.cfm?id=201220 and then there is Francis Ratnieks at Sussex who proudly describes himself as the UK’s only Professor of Apiculture http://www.sussex.ac.uk/profiles/128567.  Others who I regard as mainstream entomologists are not described as such as in their job titles, e.g. Richard Wall at Bristol, Professor of Zoology; Jane Memmott also at Bristol,  Professor of Ecology; Bill Hughes at Sussex , Professor of Evolutionary Biology; Charles Godfray at Oxford (Hope Professor of Zoology) and the list goes on.  Even Mike Siva-Jothy who describes himself as an angry old entomologist on Twitter is just listed as Professor. Unlike arachnologists in Canada who are extremely rare organisms as outlined in Chris Buddles’ great blog article http://arthropodecology.com/2013/02/06/where-are-all-the-arachnologists-and-why-you-should-care/  we are still around in fairly respectable numbers.  We do, however, seem to be making it difficult for potential students to find and identify us.  The reasons for why I think this has happened will be the subject of another blog.  The point is, that if we are hard to find and identify, then the pool of potential future entomologists is going to become smaller as fewer and fewer undergraduates are exposed to basic entomological teaching and thus fewer and fewer entomologists will make it through to academia and our profile will become even lower and therefore even fewer students will be able to be inspired and so on and so on.  As a result, we too are likely to become as endangered as Canadian arachnologists.

So, if you are an academic who works mainly with insects and you are able to identify more species than just those you work on, then why not identify yourself in your job title as an entomologist and stand tall and proud and countable.

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