Category Archives: Entomological classics

Entomological Classics – Southwood 1961 – The number of insect species associated with various trees

 

Nineteen-Sixty-One  was a momentous  year for entomology and ecology, although at the time I suspect few realised it.  Skip forward to 2013 when The British Ecological Society published a slim volume celebrating  the 100 most influential papers published in the Society’s journals.  The papers included in the booklet were selected based on the opinions of 113 ecologists from around the world, who were then asked to write a short account of why they thought that paper influential.  I was disappointed not to be asked to write about my nomination but instead asked to write about Maurice Solomon’s 1949 paper in which he formalised the term functional response.

The paper I had wanted to write about was included, but John Lawton had the privilege of extolling its virtues, and given the word limits did a pretty good job.  I do, however, feel that given its importance to ecology and entomology it deserves a bit more exposure, so I am taking the opportunity to write about it here.  I could have included this post in a series I have planned, called Ten Papers that Shook My World, but given the impact that this paper has had on entomologists I felt it deserved an entry in my Entomological Classics series.

For those of you who haven’t come across this paper before, this was an astonishingly influential paper.  Basically, Southwood, who despite his later reputation as one of the ecological greats, was an excellent entomologist, (in fact he was a Hemipterist), wanted to explain why some tree species had more insect species associated with them than others.  He made comparisons between trees in Britain, Russia and Cyprus and demonstrated that those trees that were more common and had a wider range had more insect species associated with them (Figure 1).

Southwood 1961 Fig 1

From Southwood 1961.  I was surprised to see that he had committed the cardinal error in his Figure caption of describing it as Graph and also including the regression equation in the figure pane; two things that I constantly reprimand students about!

Importantly he also showed that introduced trees tended to have fewer insects than native species.  He thus hypothesised that the number of insects associated with a tree species was proportional to its recent history and abundance and was a result of encounter rates and evolutionary adaptation.  He then tested this hypothesis using data on the Quaternary records of plant remains from Godwin (1956) making the assumption that these were a proxy for range as well as evolutionary age.

He commented on the outliers above and below the line suggesting that those above the line were a result of having a large number of congeners and those below the line either as being taxonomically isolated and/or very well defended.

He then went on to test his ideas about the evolutionary nature of the relationship by looking at trees and insects in Hawaii, (ironically this appeared in print (Southwood, 1960), before the earlier piece of work (Journal of Animal Ecology obviously had a slower turnaround time in those days than they do now).

Hawaiin figure

Figure 2.  Relationship between tree abundance and number of insect species associated with them (drawn using data from Southwood 1960).

Considering the research that these two papers stimulated over the next couple of decades, what I find really odd, is that Southwood, despite the fact that he was dealing with data from islands and that Darlington (1943) had published a paper on carabids on islands and mountains in which he discussed species-area relationships and further elaborated on in his fantastic book (Darlington, 1957), did not seem to see the possibility of using the species-area concept to explain his results.  It was left to Dan Janzen who in 1968 wrote

It is unfortunate that the data on insect-host plant relationships have not in general been collected in a manner facilitating analysis by MacArthur and Wilson’s methods (as is the case as well with most island biogeographical data). What we seem to need are lists of the insect species on various related and unrelated host plants, similarity measures between these lists (just as in Holloway and Jardine’s 1968 numerical taxonomic study of Indo- Australian islands), knowledge of the rates of buildup of all phytophagous insect species on a host plant new to a region, where these species come from, etc. Obviously, the insect fauna must be well known for such an activity. The English countryside might be such a place; it has few “islands” (making replication difficult) but a very interesting “island” diversity, with such plants as oaks being like very large islands and beeches being like very small ones, if the equilibrium number of species on a host plant (Elton, 1966; Southwood, 1960) is any measure of island size.”

 

In 1973 Dan Janzen  returned to the subject of trees as islands and cited Paul Opler’s 1974 paper in relation to the fact that the number of  herbivorous insects associated with a plant increases with the size of the host plant population (Figure 3), and further reiterated

Opler Figure

Figure 3.  Opler’s 1974 graph showing relationship between range of oak trees in the USA and the number of herbivorous insect species associated with them.

 his point about being able to consider trees as ecological islands.  Opler’s 1974 paper is also interesting in that he suggested that this approach could be used for predicting pest problems in agricultural systems, something that Don Strong and colleagues did indeed do (Strong et al., 1977; Rey et al., 1981), and that the concept of habitat islands and the species-area relationship could be used when designing and evaluating nature reserves, something which indeed has come to pass.

Again in 1974 but I think that Strong has precedence because Opler cites him in his 1974 paper, Don Strong reanalysed Southwood’s 1961 data using tree range (based on the Atlas of the British Flora)  as the explanatory variable  (figure 4) to explain the patterns seen.

Strong Figure

Figure 4Strong’s reworking of Southwood’s 1961 insect data using the distribution of British trees as shown in Perring & Walters1 (1962).

The publication of this paper opened the floodgates, and papers examining the species-area relationships of different insect groups and plant communities proliferated (e.g  leafhoppers (Claridge & Wilson, 1976); bracken (Rigby & Lawton, 1981); leaf miners (Claridge & Wilson, 1982); rosebay willow herb (McGarvin, 1982), with even me making my own modest contribution in relation to Rosaceous plants   (Leather, 1985, 1986).

Although not nearly as popular a subject as it was in the 1980s, people are still extending and refining the concept  (e.g. Brändle & Brandl, 2001; Sugiura, 2010; Baje et al., 2014).

Southwood (1961) inspired at least two generations of entomologists and ecologists, including me, and is still relevant today.  It is truly an entomological (and ecological) classic.

References

Baje, L., Stewart, A.J.A. & Novotny, V. (2014)  Mesophyll cell-sucking herbivores (Cicadellidae: Typhlocybinae) on rainforest trees in Papua New Guinea: local and regional diversity of a taxonomically unexplored guild.  Ecological Entomology 39: 325-333

Brändle, M. &Brandl, R. (2001). Species richness of insects and mites on trees: expanding Southwood. Journal of Animal Ecology 70: 491-504.

Claridge, M. F. &Wilson, M. R. (1976). Diversity and distribution patterns of some mesophyll-feeding leafhoppers of temperate trees. Ecological Entomology 1: 231-250.

Claridge, M. F. &Wilson, M. R. (1982). Insect herbivore guilds and species-area relationships: leafminers on British trees. Ecological Entomology 7: 19-30.

Darlington, P. J. (1943). Carabidae of mountains and islands: data on the evolution of isolated faunas and on atrophy of wings. Ecological Monographs 13: 37-61.

Darlington, P. J. (1957). Zoogeography: The Geographical Distribution of Animals. New York: John Wiley & Sons Inc.

Elton, C. S. (1966). The Pattern of Animal Communities. Wiley, New York.

Holloway, J. D., & Jardine, N. (1968). Two approaches to zoogeography: a study based on the distributions of butterflies, birds and bats in the Indo-Australian area. Proceedings of the Linnaean Society. (London) 179:153-188.

MacArthur, R. H. & Wilson, E.O. (1967). The Theory of Island Biogeography. Princeton University Press, Princeton, N. J

Janzen, D. H. (1968). Host plants as islands in evolutionary and contemporary time. American Naturalist 102: 592-595.

Janzen, D. H. (1973). Host plants as islands II.  Competitive in evolutionary and contemporary time. American Naturalist 107: 786-790.

Kennedy, C.E.J. & Southwood, T.R.E. (1984) The number of species of insects associated with British trees: a re-analysis. Journal of Animal Ecology 53: 455-478.

Leather, S. R. (1985). Does the bird cherry have its ‘fair share’ of insect pests ? An appraisal of the species-area relationships of the phytophagous insects associated with British Prunus species. Ecological Entomology 10: 43-56.

Leather, S. R. (1986). Insect species richness of the British Rosaceae: the importance of hostrange, plant architecture, age of establishment, taxonomic isolation and species-area relationships. Journal of Animal Ecology 55: 841-860.

Macgarvin, M. (1982). Species-area relationships of insects on host plants: herbivores on rosebay willowherbs. Journal of Animal Ecology 51: 207-223.

Opler, P. A. (1974). Oaks as evolutionary islands for leaf-mining insects. American Scientist 62: 67-73.

Perring, F.J. & Walters, S.M. (1962) Atlas of the British Flora BSBI Nelson, London & Edinburgh.

Preston,  C.D., Pearman, D.A. & Tines, T.D. (2002) New Atlas of the British and Irish Flora: An Atlas of the Vascular Plants of Britain, Ireland, The Isle of Man and the Channel Islands. BSBI, Oxford University Press

Rigby, C. & Lawton, J. H. (1981). Species-area relationships of arthropods on host plants: herbivores on bracken. Journal of Biogeography 8: 125-133.

Solomon, M. E. (1949). The natural control of animal populations. Journal of Animal Ecology 18: 1-35

Southwood, T. R. E. (1960). The abundance of the Hawaiian trees and the number of their associated insect species. Proceedings of the Hawaiian Entomological Society 17: 299-303.

Southwood, T. R. E. (1961). The number of species of insect associated with various trees. Journal of Animal Ecology 30: 1-8.

Sugiura, S. (2010). Associations of leaf miners and leaf gallers with island plants of different residency histories.  Journal of Biogeograpgy 37: 237-244

Rey, J.R.M.E.D. & Strong, D.R. (1981) Herbivore pests, habitat islands, and the species area relation. American Naturalist 117: 611-622.

Strong, D. R. (1974). The insects of British trees: community equilibrium in ecological time. Annals of the Missouri Botanical Gardens 61: 692-701.

Strong, D.R., D., M.E., & Rey, J.R. (1977) Time and the number of herbivore species: the pests of sugarcane. Ecology 58: 167-175

 

1Postscript

The Atlas of the British Flora by Perring and Walters (1962) was an iconic piece of work, although not without its flaws.  As with many distribution atlases it is based on a pence or absence score of plant species within one kilometre squares.  So although it is a good proxy or range it does not necessarily give you an entirely reliable figure for abundance.  A dot could represent a single specimen or several thousand specimens.   Later authors attempted to correct for this by using more detailed local surveys e.g. tetrads.  It must have been particularly galling for  Southwood that the Atlas didn’t appear until after he had published his seminal papers, but he later made up for it by reanalysing and extending his data from that original 1961 paper (Kennedy et al., 1984).

Those of us working in this area using the original Atlas had to count the dots by hand, a real labour of love especially for those widely distributed species; the new edition (Preston et al., 2002) actually tells you how many dots there are so the task for the modern-day insect-plant species-area relationship worker is much easier 😉

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Entomological classics – The Malaise Trap

More years ago than I care to remember, my friends and I were playing the now, very non-PC game of Cowboys and Indians, when we saw through the trees, what we thought was a tent. On sneaking up to it we found that, if it was a tent, it wasn’t very watertight!  There were no sides, instead there was a central panel and the whole thing was made of netting.  What we had actually found, was of course a Malaise trap, although of course we did not know this at the time.  It was only later as an undergraduate that I realised what we had found all those years before.

So exactly what is a Malaise trap and how did it come into being? The Malaise Trap is a relatively new invention.  It was invented by the Swedish entomologist, Dr René Malaise in the 1930s (hence the name) and revealed to a more general entomological audience in 1937 (Malaise, 1937).  It was actually designed as a replacement for the traditional hand-held collecting net, which as Malaise states in the introduction to his paper ‘”Since the time of Linneaus, the technique of catching insects has not improved very much, and we are to-day using the same kind of net as then for our main instrument”.

I was amused, when reading on further, to find that my childhood gaffe of confusing a Malaise Trap with a net was fully justified. Malaise, later in the same paper writes, ”During my extensive travels I have repeatedly found that insects happened to enter my tent, and that they always accumulated at the ceiling-corners in vain efforts to escape at that place without paying any attention to the open tent door”. He then goes on to describe how he conjectured that “a trap made as invisible as possible and put up at a place where insect are wont to patrol back and forth, might catch them much better than any tent, and perhaps better than a man with a net, as a trap could catch them all the time, by night as by day, and never be forced to quit catching when it was best because dinner-time was at hand”.

He thus set about constructing a trap based on the idea of an open tent with a collecting device attached to the central end pole to take advantage of the fact that most insects when encountering an obstacle tend to fly upwards. On reaching the apex of the tent, the only way out is into the collecting device which is filled with a killing agent.  It is in effect, a flight intercept trap, but unlike window traps (subject of a later post), the insects instead of falling into a collecting device, head upwards and collect themselves. Malaise tested his first version of the trap on an expedition to Burma and found them to be a great success “every day’s catch from the traps grew larger and larger, and sorting it required more and more time”. He found the traps particularly good for Diptera and Hymenoptera but also very good for Coleoptera and Noctuid and Sphingid moths.  He also mentions catching Hemiptera.

In outward form, the Malaise Trap has remained fairly unchanged since its invention. The first versions were apparently fairly heavy, having a brass insect collecting cylinder and also only had one opening.  Malaise recognised the disadvantages of the single entrance version and suggested in the 1937 paper that a bilateral model would be more effective.  These followed in due course. Modified versions using plastic cylinders and different netting material were  invented in the 1960s (Gressit & Gressit, 1962; Townes, 1962; Butler, 1965).  Townes’s paper gives a very detailed description of the construction and use of modified Malaise traps (90 pages) in contrast to Butler’s three page description of a cheap and cheerful version made from a modified bed-net.

Nowadays, entomologists world-wide, particularly Dipterists and Hymenopterists, use Malaise traps of various designs and colours, and cost.  In the UK they are available from commercial outlets at prices ranging from £60 to £165. They are extremely effective and we use them to collect insects for our practical classes in the Entomology MSc based at Harper Adams University.

    Malaise traps

Malaise trap in operation, Harper Adams University, Shropshire, UK.

 

References

Butler, G.D. 91965) A modified Malaise insect trap. The Pan-Pacific Entomologist, 41, 51-53

Gressitt, J.L. & Gressitt, M.K. (1962) An improved Malaise Trap. Pacific Insects, 4, 87-90

Malaise, R. (1937) A new insect-trap.  Entomologisk Tidskrift, Stockholm, 58, 148-160

Townes, H. (1962) Design for a Malaise trap. Proceedings of the Entomological Society of  Washington, 64, 162-253

 

Post script

Malaise was not just an entomologist; he was an explorer and a passionate believer in the existence of Atlantis. A detailed biography of this extraordinary character can be found here, including a photograph of the original Malaise trap.

 

Post post script

I was amused to find in the 1949 edition of Instructions for Collectors No. 4a, Insects (Smart, 1949), this somewhat dismissive comment about the Malaise Trap “It is a very novel idea and captures large numbers of insects, but as at present designed is rather cumbersome, and since its design will probably be modified with experience it is not described here

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Entomological Classics – The Pooter or Insect Aspirator

I’m sure that we can all remember our first encounter with that wonderful entomological device, The Pooter and were probably all told to remember to  “suck don’t blow” and also to remember to suck from the right tube.  Despite this sage advice I am also sure that most, if not all of us, have somehow managed to end up with a mouthful of small insects 😉

pooter classic

 

The Pooter as I came across it first as a student – inherently simple but incredibly breakable http://svalbardinsects.net/index.php?id=33

So exactly what is a Pooter and when was it invented?  I of course knew the answer to the first bit but had forgotten the answer to second (if I ever knew it).  I decided to see what Google would reveal.  A quick Google search led me to this simple definition from http://brainsofsteel.co.uk/post.php?id=Looking-for-Life-in-Your-own-Back-Yard

  “The pooter (sic – pedantically as it is named after a person so should be capitalised) is said to get it’s wonderful name from William Poos an American entomologist active in the 1930s, it consists of a small transparent airtight vial with two tubes protruding.  One tube is put in your mouth and the other acts as a vacuum that will suck up bugs safely without damaging them.  There is an inherent risk of sucking a bug into your mouth but that is half the fun.”

and this one here from http://www.oxforddictionaries.com/definition/english/pooter

Pooter definition

and from A Dictionary of Entomology,  Gordon Gordh & David Headrick  CABI 2011 Second Edition.

Pooter noun

So it definitely seemed to appear that the Pooter was a relatively recent invention.  Was this true or was it the entomological equivalent of an urban myth? I started with finding out a bit more about the putative inventor of the Pooter, F.W.  Poos and found this also in the same source

Poos obit short

 

and after tracking down the obituary by T E Wallenmaier was rewarded with a photograph of the great man.

Poss Picture

Next I got hold of Poos’s 1929 paper in which he described the insect aspirator and sure enough there was a diagram of a Pooter pretty much as we know it today but with a cigarette holder as the mouthpiece.

Poo's Pooter

In his paper Poos notes that his design is a modified version of the aspirators used by Kunkel (1926) and Severin & Swezy (1928). So how modified was his design and should the Pooter really be called the Pooter?  In the Severin and Swezy paper we are lucky enough to have a photograph of the insect aspirator in action and it is very obviously a straight line system as opposed to the two tubes going in at the top and the text explains that  once caught the catch is tapped into another tube or vial.

Severin Swezy picture

So what about the earlier Kunkel paper?  In this case the photograph clearly shows a sucking tube and another tube in which the

Kunkel Pooter

catch is placed by blowing it out of the collecting tube; the Poos version is clearly a more efficient device as you suck and catch and can store your catches until a convenient moment arises for transfer to either your killing jar or observation  chamber.  As an undergraduate I briefly trialed a Pooter containing cherry laurel  (Prunus laurocerasus) to make a combined catching and killing device; needless to say I very quickly decided that it was not a good idea.

So the Pooter is distinct from the other devices in that the catch does not have to be transferred immediately to another container and that it has the sucking and catching ends coming out of the same aperture.  Interestingly enough I did find an earlier description of an insect aspirator that had the same properties as the Pooter but was a straight line system (Buxton, 1928).  So is the criterion

 

Buxton Pooter

 

for a Pooter the two tubes emanating from the same source?  Apparently not as I have found these all described as pooters (sic).

 

Pooters

Despite all my searching and a resort to Twitter, the earliest reference to an insect aspirator that I could find (many thanks to Richard Jones also known as @Bugmanjones) was 1868 and is basically the same device as that described by Severin and Swezy in 1929.

Precursor Pooter

So if we accept that the Pooter is the classic two tube sucker-storage version then yes, Poos invented the Pooter.  If we contend that the Pooter is any old insect aspirator then it seems that Ormerod got there first and we should perhaps only be calling it a pooter  because of the noise we make when aspirating an insect 😉

References

Gibb, T.J. & Oseto, C.Y. (2006) Arthropod Collection and Identification: Laboratory and Field Techniques.  Academic Press , New York

Kunkel, L.O. (1926) Studies on Aster Yellows.  American Journal of Botany, 13, 646-705

Poos, F.W. (1929) Leaf hopper injury to legumes.  Journal of Economic Entomology, 22, 146-153

Severin, H.P. & Swezy, O. 91928) Filtration experiments on curly top of sugar beets.  Phytopathology, 18, 681-691

Wallenmaier, T.E. (1989) Poos, Frederick, William-1891-1987-Obiturary. Proceedings of the Entomological Society of Washington , 91, 298-301

 

Post script

I knew I would regret throwing out my old copies of Antenna when I moved to Harper Adams.  During my research I came across a reference to some correspondence in Antenna in 1982.

Obit excerpt

 

Luckily, Val McAtear, the Librarian at the Royal Entomological Society, very kindly scanned in the relevant pages for me.  To my chagrin, I found that I would have saved myself a lot of time if I had remembered this article (Fergusson, N.D.M. (1982)  Pooter Post. Antenna,  282-284).  On the plus side, I had, however, found several references to insect aspirators that he had not.  His additional references are shown below in case anyone wants to track them down.

Baden, E.B. (1951)  Collecting beetles associated with stored food products.  Amateur Entomologist Leaflet 6, 1-9

Cogan, B.H. & Smith, K.G.V. (1974) Instructions for Collectors.  British Museum (Natural History).

Colyer, C.N. & HJammond, C.O. (1951) Flies of the British Isles, Frederick Warne & Co. Ltd.

Hurd, P.D. (1954) ‘Myiases’ resulting from the use of the Aspirator method in the collection of insects.  Science, 119, 814-815

Lewis, D.J.  (1933)  Observations on Aedes aegypti L. (Dipt., Culic.) under controlled atmospheric conditions.  Bulletin of Entomological Research, 24, 363-372

Myers, E.H. (1933) A mouth pipette and containers for smaller organisms.  Science, 77, 609-610

Oldroyd, H. (1958) Collecting, Preserving and Studying Insects.  Hutchinson, London.

O’Rourke, F.J. (1939) Ant collecting.  Amateur Entomologist, 4, 33-34

Perkins, J.F. (1943) The collecting trip, in the Hymenopterist’s Handbook.  Amateur Entomologist, 7, 140-147

Philip, C.B. (1931) Two new species of Uranotaenia (Culicidae) from Nigeria, with notes ion the genus in the  Ethiopian region.  Bulletin of Entomological Research, 22, 183-193

Psota, F.J. (1916) A suction-pump collector.  Entomological News, 27, 22-23

Wishart, G. (1930) Some devices for handling insects.  Journal of Economic Entomology, 23, 234-237

 

Post  post script

Two curiosities that I came across in my foray into the depths of insect aspirator history was a patent filed in 1938 by a Clyde Barnhart for an aspirator designed to reduce wear and tear on the operator

Pooter patent

And a mechanical aspirator powered by a car engine (Moore, H,.W. (1943)  A mechanical aspirator of sorting and collecting insects in the field.  Canadian Entomologist, 75, 162).

And finally

It appears that in the USA poot is analogous to fart!

Pooter tooter

And now sadly, available in the UK for a mere £12.99 – http://www.thepooter.co.uk/

Pooter tooter UK

But the good news is that you can get a real Pooter (albeit plastic) for much less , £1.79 to be precise 😉

Pooter Invicta

http://www.rapidonline.com/science/invicta-insect-pooter-517018

 

 

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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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Entomological classics – The clip cage

Mention clip cage to an aphidologist and the chances are that they will smile and begin reminiscing about the days when they had to sit down and spend hours refurbishing and making new ones; if they were lucky enough to be in a big research group as I was, they will have had the fun of the communal clip cage renovation day, otherwise they will have laboured doggedly away on their own.  Mention clip cage to an entomologist and they may have heard of them, but probably not used them; to a non-entomologist you will be talking gibberish.  In fact, this week at the beginning of a lecture to the MSc Entomology course here at Harper Adams, I held a clip cage in the air and asked those who knew what it was to put their hands in the air, less than a third were willing to hazard a guess.  For those of you who don’t know the answer, clip cages were invented, or at least revealed in the scientific literature by two Canadian entomologists MacGillivray & Anderson in 1957.  Their purpose, to keep aphids confined individually to leaves of a plant in a simple and effective way.

Clip cages in action

Before this aphidologists generally used to confine them in large cages covering whole plants, (Davidson, 1925; Kennedy & Booth, 1950).  This allowed the aphids to select their own feeding sites but which of course made knowing what an individual aphid was doing in terms of longevity and fecundity quite difficult.  Kennedy & Booth (1950) were very much aware of this and attempted to solve the problem by using this using this rather over-engineered reproduction cage

Kennedy reproduction cage

This cage, although doing the job was difficult to make and also required a somewhat complicated method of attachment to the plant so as not to pull the leaves off, hence the birth of the

Kennedy leaf cages

MacGillivray  and Anderson clip cage.  In 1958 another Canadian entomologist Noble described a variant on the MacGillivray & Anderson version where instead of a muslin lid, a cork was used , the theory being that you didn’t need to open the clip to check what the aphid was doing and risk it falling off the leaf, something aphids seem to delight in doing , especially when you are six

 Noble Clip cage

 days into obtaining seven-day fecundity readings!  Incidentally, this version of the clip cage has resulted in one of my favourite bug-bears, as many people tend to cite Noble (1958) when referring to clip cages, that is if they actually remember to cite anyone at all, and of course they are using the MacGillivray & Anderson version.

Since then the humble clip cage has become the standard way for aphidologists to keep aphids on single leaves of their hosts plants.  They have also been used to confine young Lepidopteran larvae to leaves (Moore et al, 2003) but due to the frass production of lepidopteran larvae are better suited to aphids whose honeydew causes less of a problem for cage cleanliness.  They are very versatile and can be made in different sizes to suit the host plant.   All you need are hair clips,  Perspex tubing and the wherewithal to cut it to the right size, some foam or sponge, fine muslin or  similar textile and a waterproof adhesive.

Clip cages      Big clip cages

Clip cages are not perfect. There are some drawbacks;  for example, if you don’t move them slightly every day the leaves can develop chlorosis which of course will change the performance of the  aphids  and there is some evidence that the leaf can suffer some physical damage (Moore et al,  2003) and that even if you do move the cages the aphids can behave slightly differently than those in  whole plant cages (Awmack & Leather (2007), but as long you are aware of the possible drawbacks  clip cages remain an indispensable tool for those wishing to study single aphids on whole plants.

And of course, there is the immense satisfaction and sense of achievement of being able to make your own equipment relatively simply and inexpensively.  That said, I certainly received some strange looks when I was working in  Finland and found that there were no clip cages in the lab and had to attempt to buy hair clips in  down-town Helsinki.

Awmack, C. S. & Leather, S. R. (2007).Growth and development. In Aphids as Crop Pests, 135-151 (Eds H. F. Van Emden and R. Harrington). Wallingford: CABI.

Davidson, J. (1925) Biological studies of Aphis ruimicis Linn. factors affecting the infestation of Vicia faba with Aphis rumicis.  Annals of Applied Biology, 12, 472-507

Evans, A.C. (1938) Physiological relationships between insects and their host plants I. The effect of the chemical composition of the plant on reproduction and production of winged forms in Brevicoryne brassicae L. (Aphididae).  Annals of Applied Biology, 25, 558-572

Kennedy, J.S. & Booth, C.O. (1950) Methods for mass rearing and investigating the host relations of Aphis fabae Scop.  Annals of Applied Biology, 37, 451-470

MacGillivray, M. E. &Anderson, G. B. (1957). Three useful insect cages. Canadian Entomologist 89: 43-46.

Noble, M. D. (1958). A simplified clip cage for aphid investigations. Canadian Entomologist 90, 60.

Moore, J.P., a, J.E., Paul, N.D. & Whittaker, J.B. ( 2003)  The use of clip cages to restrain insects    reduces leaf expansion systemically in Rumex obtusifolius Ecological Entomology, 28, 239-242

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