Pick and Mix 29 – More stuff that caught my eye

What happens when you microwave two grapes and why

What happens if all the insects disappear?

Artists illustrating the digital collection at  The Natural History Museum London

Erica McAlister writes about the wonderful Dark-Edged Bee Fly

More from Erica on the wonders of flies

Growing carrots in bottles

Spanish salt pans, conservation and bird migrations

Interactions between fire and butterflies – how prescribed burning helps rare species

Successful eradication of an invasive species

This might upset a few people – is the term rewilding just a trendy buzzword for restoration?



Leave a comment

Filed under Pick and mix

Green islands – safe and healthy in a sea of death

Those of you whom work in forests, will, I am sure, be familiar with the term “green island”.  To a forester or forest entomologist, a green island is a clump of trees that have, for some reason or other, survived the ravages of an insect outbreak.  The earliest reference I can find to this phenomenon is in a 1927 paper by the German myrmecologist Hermann Eidmann (1897-1949), who described them as green oases, or, as the paper was written in German, more correctly, “grüne Oasen” (Eidmann, 1927).

Red wood ants helping maintain a “grüne Oasen”   green oasis” in a German pine forest (Eidman, 1927).

As well as “farming aphids” to obtain sugar from their honeydew, ants also have a similar mutualistic relationship with plants that give them a sugary reward to protect them from herbivorous insects, except those that also provide the ants with sugar (Janzen 1966; Bentley, 1977).  The mutualisms can be very sophisticated. In Michigan, the North American black cherry, Prunus serotina, times nectar production from its extra-floral nectaries to attract the ant Formica obscuripes  when the larvae of its major herbivore, the eastern tent caterpillar, Malacosoma americanum are at their most vulnerable (Tilman, 1978).  Trees that are protected have greatly reduced levels of herbivory. When more than one ant colony is involved, rather than single trees being protected, a group of trees can be saved from defoliation, and form a green island.  The areas covered by these green islands can be quite extensive, for example two ant colonies of the ant  Formica polyctena were enough to protect pine trees from the nun moth Lymantria monacha in Sweden within a 45 m diameter around the colonies (0.16 ha) (Wellenstein, 1980) and green islands of up to 3 ha have been reported (Eidmann, 1927).

Left – canopy of trees near ant nests, on the right, trees not close to ant nests Wellenstein (1980)


In Finland, one colony of the ant F. aquilonia is enough to create subarctic mountain birch (Betula pubescens), green islands of up to 0.12 ha in area (Laine & Niemelä, 1980).

Green islands attributed to the activity of the ant Formica aquilonia in subarctic Finland (Laine & Niemela, 1980).

It would seem that the case for the ants protecting the trees against defoliating herbivores and being the cause for the green islands is very convincing.  Tom White, never one to avoid a controversy, disagreed. He suggested that it was the nest building activities of the ants that were the cause for the green islands, the refuse dumps provide higher concentrations of nutrients that the roots of surrounding trees can access and additionally soil moisture conditions are improved, both these factors encouraging more vigorous growth in those trees close to ant nests, making them less palatable to herbivores (White, 1985).   The Finnish team responded to this with some additional data and arguments defending their hypothesis (Niemelä & Laine, 1986) and there the matter rested, for a while at least. Not satisfied with their post hoc response, the Finns came up with, to me at any rate, a very convincing field experiment where they showed that soil nitrogen did not vary significantly with distance from ant nests and that birch leaf nitrogen content and moth larval growth rates and survival were also not affected by distance from ant nests (Karhu, 1998; Karhu & Neuvonen, 1998), indicating that the green islands were indeed, due to predation by the ants and not improved tree nutrition.

Soil nitorgen in realtion to distance from ant colonies (Karhu & Neuvonen, 1998).

You might think that this would be the last word, but you would be wrong 🙂  The Karhu and Neuvonen paper, is, in the journal, followed by a “comment” paper by no less a person than Tom White (White 1998) in which he disputes in no uncertain terms, their interpretation of their new data.  Matthias Schaefer, the then Editor of Oecologia, felt that some sort of explanation was needed and added a final note to the saga, which in itself makes very interesting reading.  I get the feeling that there were some strong emotions involved 🙂

Pouring oil on troubled water – wise words from Editor-in-Chief Mathias Schaefer



Bentley, B.L. (1977) Extrafloral nectaries and protection by pugnacious bodyguards. Annual Review of Ecology & Systematics, 8, 407-427.

Eidmann, H. (1927) Weitre Beobachtungen über den Nutzen de roten Waldameise.  Anzeiger für Schädlingskunde, 3, 49-51.

Janzen D.H. (1966) Coevolution of mutualism between ants and Acacias in Central America. Evolution, 20, 249-275.

Kaiser, W., Huguet, E., Casas, J., Commin, C. & Giron, D. (2010)  Plant green-island phenotype induced by leaf-miners is mediated by bacterial symbionts. Proceedings of the Royal Society B, 277, 2311-2319.

Karhu, K.J. (1998) Effects of ant exclusion during outbreaks of a defoliator and a sap-sucker on birch. Ecological Entomology, 23, 185-194Kah.

Karhu, K.J. & Neuvonen, S. (1998) Wood ants and a geometrid defoliator of birch: predation outweighs beneficial effects through the host plant. Oecologia, 113, 509-516.

Laine, K.J. & Niemela, P. (1980) The influence of ants on the survival of mountain birches during an Oporinia autumnata (Lep., Geometridae) outbreak. Oecologia, 47, 39-42.

Niemela, P. & Laine, K.J. (1986) Green islands – predation not nutrition. Oecologia, 68, 476-478.

Tilman, D. (1978) Cherries, ants and tent caterpillars: timing of nectar production in relation in relation to susceptibility of caterpillars to ant predation. Ecology, 59, 686-692.

Wellenstein, G. (1980) Auswirkung hügelbauender Waldameisen der Formica rufa‐Gruppe auf forstschädliche Raupen und das Wachstum der Waldbäume. Zeitschrift für Angewandte Entomologie, 89, 145-157.

White, T.C.R. (1985) Green islands – nutrition not predation – an alternative hypothesis. Oecologia, 67, 455-456.

White, T.C.R. (1998) Green islands – still not explained.  Oecologia, 113, 517-518.


Leave a comment

Filed under EntoNotes

The Verrall Supper 2019 – entomological convivality

For many entomologists The Rembrandt Hotel in South Kensington and the first Wednesday of March means only one thing – the Verrall Supper. I report on the activities of the Verrall Association annually and if you click on this link you will be able to work your way back through previous reports to my very first attempt.  This will, once again, be largely a photographic record.  This year the first Wednesday of March was the 6th but despite the date of the Supper always being the first Wednesday in March it still seemed to have caught a few Verrallers by surprise.  Consequently numbers were slightly down compared with last year’s, although the number of non-attending Verrallers paying to retain their membership was at an all-time high.  One notable absence, due to a slipped disc, was Richard Lane, the newly elected Treasurer of the Entomological Club, under whose auspices, the Verrall Association is privileged to run.

More positively we were slightly up on female entomologist this year, 36 % compared with last year’s 32%.  There is still much progress to be made, but we have seen a year on year increase now for the last four years so, perhaps one day we will hit that magic 50:50 mark.

I performed a humanist blessing, which seemed to meet with satisfaction from all sides, and unbeknownst to me was caught on video by one of the Verrallers  I reproduce it here if anyone feels like using it at a similar occasion.

As we come together at this special time, let us pause a moment to appreciate the opportunity for good company and to thank all those past and present whose efforts have made this event possible. As we go through life, the most important thing that we can collect is good memories.  Thank you for all being here today to share this meal as a treasured part of this collection.

And now as the old cliché goes, let the pictures tell the story.

Clive Farrell doing his usual stint on the Registration Desk.  Something seems to be puzzling him?

Max Barclay presenting Professor Helmut van Emden with a copy of the latest Royal Entomological Society Handbook, Beetle Larvae.  Van’s father was a Coleopterist who started this book more than fifty years ago, hence the presentation.

Pre-Supper drinks – and some evidence that not all Verrallers are gray, male and balding, although many are 🙂

The Wyebugs Team – Mike Copland and Sue Stickels – Ray Cannon in the background talking with Keith Walters and Roger Booth

And here they are revealed!

People with drinks including the President of the Royal Entomological Society Chris Thomas, doing some arm-waving, and the rather too-long queue for the bar.  There was supposed to be another bar but there was an electrical fault.

The next set of photographs are what I describe as ‘Ento Bling’. When it comes to “smart casual”, which is the dress code for the Verrall Supper, I feel that in most cases, it is easier for female entomologists to show their dedication to insects than the male of the species, alternatively, perhaps males are just less imaginative and go for the easy tie option 🙂

The food, as usual, was excellent and most tables seemed to have a healthy mix of entomologists of different age classes and sex.

You try your best but bald heads keep appearing 🙂


And finally, I wonder who this was?  🙂  I’ll give you a clue – she is a Dipterist!

 Many thanks to all who attended and I hope to see you all again next year plus many new faces.



Leave a comment

Filed under Uncategorized

Pick and Mix 28 – some video treats

A very interesting, if somewhat gruesome video, of a botfly larva being removed from a human

Continuing with the fly stuff, here are some maggots having an evening meal 🙂 Seriously though, the article is all about using insects as food

And continuing with flies and food – don’t forget that bees are not the only pollinators

Now some hungry mosquitoes, which are of course. also flies

More flies – this time on how to stop them eating your wheat crop

Cockroach farming for food and medicine

Beetles like light too

Magnificent Monarchs in flight – a moving experience

A musical introduction to insect orders

A moving video from a teenage girl about insect extinction


Filed under Pick and mix

“Insectageddon” – bigger headlines, more hype, but where’s the funding?

Unless you have been hibernating in a deep, dark cave or on another planet, you can hardly have missed the ‘insectageddon’ media frenzy that hit the UK (and elsewhere) on Monday (11th February).

This time the stimulus was a review paper outlining the dramatic decline in insect numbers, from two Australian authors (Sánchez-Bayo & Wyckhus, 2019).  Their paper, based on 73 published studies on insect decline showed that globally, 41% of insect species are in decline, which is more than twice that reported for vertebrates.  They also highlighted that a third of all insect species in the countries studied are threatened with extinction.  Almost identical figures were reported some five years ago (Dirzo et al., 2014), but somehow escaped the attention of the media.

I’m guessing that a clever press release by either the authors’ university or from the publisher of Biological Conservation set the ball rolling and the appearance of the story in The Guardian newspaper on Monday morning got the rest of the media in on the act.

The headline that lit the fuse – The Guardian February 11th  2019

The inside pages

A flurry of urgent phone calls and emails from newspapers, radio stations and TV companies resulted as the various news outlets tried to track down and convince entomologists to put their heads above the parapet and comment on the story and its implications for mankind.  I was hunted down mid-morning by the BBC, and despite not being in London and recovering from a bad cold, was persuaded to appear live via a Skype call.  A most disconcerting experience as although I was visible to the audience and interviewer, I was facing a blank screen, so no visual cues to respond to.  According to those who saw it, it was not a disaster 🙂  Entomologists from all over the country, including at least three of my former students, were lured into TV and radio studios and put through their entomological paces.

Me, former student Tom Oliver (University of Reading), Blanca Huertas (NHM) and former student Andy Salisbury (RHS Wisley), getting our less than fifteen minutes of fame 🙂

As far as I know, we all survived relatively unscathed and the importance of insects (and entomologists) for world survival was firmly established; well for a few minutes anyway 🙂

It is the ephemeral nature of the media buzz that I want to discuss first.  Looking at the day’s events you would be forgiven that the idea of an ecological Armageddon brought about by the demise of the world’s insects was something totally new.   If only that were so.

Three years of insect decline in the media

The three years before the current outbreak of media hype have all seen similar stories provoking similar reactions, a brief flurry of media attention and expressions of concern from some members of the public and conservation bodies and then a deafening silence. Most worrying of all, there has been no apparent reaction from the funding bodies or the government, in marked contrast to the furore caused, by what was, on a global scale, a relatively minor event, Ash Die Back.  Like now, I responded to each outcry by writing a blog post, so one in 2016, one in 2017 and another last year.

So, will things be different this time, will we see governments around the world, after all this is a global problem, setting up urgent expert task forces and siphoning research funding into entomology? Will we see universities advertising lots of entomologically focused PhD positions?  I am not hopeful. Despite three years of insectageddon stories, the majority of ecology and conservation-based PhDs advertised by British universities this autumn, were concerned with vertebrates, many based in exotic locations, continuing the pattern noted many years ago. In terms of conservation and ecology it seems that funding is not needs driven but heavily influenced by glamorous fur and feathers coupled with exotic field sites (Clarke & May, 2002).

The paper that caused the current media outbreak (Sánchez-Bayo & Wyckhus, 2019) although hailed by the media as new research, was actually a review of 73 papers published over the last several years.  It is not perfect, for one thing the search terms used to find the papers used in the review included the term decline, which means that any papers that did not show evidence of a decline over the last forty years were not included e.g. Shortall et al. (2009; Ewald et al. (2015), both of  which showed that in some insects and locations, populations were not declining, especially if the habitats that they favoured were increasing, e.g. forests, a point I raised in my 2018 post.  Another point of criticism is that the geographic range of the studies was rather limited, almost entirely confined to the northern hemisphere (Figure 1). Some commentators have also criticised the analysis, pointing out that it was

Figure 1. Countries from which data were sourced (Sánchez-Bayo & Wyckhus, 2019).

not, as stated by the authors, a true meta-analysis but an Analysis of Variance.  Limitations there may be, but the take home message that should not be ignored, is that there are many insect species, especially those associated with fresh water, that are in steep decline.  The 2017 paper showing a 75% reduction in the biomass of flying insects in Germany (Hallmann et al., 2017), also attracted some criticism, mainly because although the data covered forty years, not all the same sites were sampled every year.  I reiterate, despite the shortcomings of both these papers, there are lots of studies that show large declines in insect abundance and they should not be taken lightly, or as some are doing on Twitter, dismissing them as hysterical outpourings with little basis in fact.


It is extremely difficult, especially with the lack of funding available to entomologists to get more robust data.  The Twitter thread below from Alex Wild, explains the problems facing entomologists much more clearly and lucidly than I could.  Please read it carefully.

Masterly thread by Alex Wild – millions of insects, millions of ways to make a living and far too few entomologists

I am confident that I speak for most entomologists, when I say how frustrated we feel about the way ecological funding is directed.  Entomologists do get funding, but a lot of it is directed at crop protection. Don’t get me wrong, this is a good thing, and something I have benefited from throughout my career.  Modern crop protection aims to reduce pesticide use by ecological means, but we desperately need to train more entomologist of all hues and to persuade governments and grant bodies to fund entomological research across the board, not just bees, butterflies and dragonflies, but also the small, the overlooked and the non-charismatic ones  (Leather & Quicke, 2010).  A positive response by governments across the world is urgently needed.  Unfortunately what causes a government to take action is hard to understand as shown by how swiftly the UK government responded to the globally trivial impact of Ash Die Back but continues to ignore the call for a greater understanding of the significance of and importance of insects, insectageddon notwithstanding.

I put the blame for lack of entomological funding in the UK on the way that universities have been assessed in the UK over the last twenty years or so (Leather, 2013). The Research Excellence Framework and the way university senior management responded to it has had a significant negative effect on the recruitment of entomologists to academic posts and this has of course meant that entomological teaching and awareness of the importance of  insects to global health has decreased correspondingly.

I very much hope that this current outbreak of media hype will go some way to curing the acute case of entomyopia that most non-entomologists suffer from. I  fear however, that unless the way we teach biology in primary and secondary schools changes, people will continue to focus on the largely irrelevant charismatic mega-fauna and not the “little things that run the world”

Perhaps if publicly supported conservation organisations such as the World Wide Fund for Nature concentrated on invertebrates a bit more that would help.  A good start would be to remove the panda, an animal that many of us consider ecologically irrelevant from their logo, and replace it with an insect. Unlikely I know, but if they must have a mammal as their flagship species, how about sloths, at least they have some ‘endemic’ insect species associated with them 🙂


Ceballos, G., Ehrlich, P.R. & Dirzo, R. (2017) Biological annihilation via the ongoing sixth mass extinction signalled by vertebrate population losses and declines. Proceedings of the Natural Academy of Sciences, 114, E6089-E6096.

Clark, J.A. & May, R.M. (2002) Taxonomic bias in conservation research. Science, 297, 191-192.

Dirzo, R., Young, H.S., Galetti, M., Ceballos, G., Isaac, N.J.B., & Collen, B. (2014) Defaunation in the anthropocene. Science, 345, 401-406.

Ewald, J., Wheatley, C.J., Aebsicher, N.J., Moreby, S.J., Duffield, S.J., Crick, H.Q.P., & Morecroft, M.B. (2015) Influences of extreme weather, climate and pesticide use on invertebrates in cereal fields over 42 years. Global Change Biology, 21, 3931-3950.

Hallmann, C.A., Sorg, M., Jongejans, E., Siepel, H., Hofland, N., Schwan, H., Stenmans, W., Müller, A., Sumser, H., Hörren, T., Goulson, D. & de Kroon, H. (2017) More than 75% decline over 27 years in total flying insect biomass in protected areas. PLoS ONE. 12 (10):eo185809.

Leather, S.R. (2013) Institutional vertebratism hampers insect conservation generally; not just saproxylic beetle conservation. Animal Conservation, 16, 379-380.

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

Sánchez-Bayo, F. & Wyckhus, K.A.G. (2019) Worldwide decline of the entomofauna: A review of its drivers. Biological Conservation, 232, 8-27.

Shortall, C.R., Moore, A., Smith, E., Hall, M.J., Woiwod, I.P., & Harrington, R. (2009) Long-term changes in the abundance of flying insects. Insect Conservation & Diversity, 2, 251-260.


Filed under EntoNotes

Pick and Mix 27 – some things I found of interest; perhaps you will too?

Not a painting, but a photograph I took through the train window – in between Sete and Montpellier


Even hares eat meat sometimes

Continuing the carnivorous theme, an Interesting article about pitcher plants

The iconic palm trees of the south of France are under threat

Hope for the future?  Blog post by Joern Fischer about sustainability

And here Jeff Ollerton reflects on the above

Another name for biodiversity offsetting, but it still doesn’t add up

A call for more common names for moths

How insect art can become entomological outreach

Ted MacRae on his latest insect collecting trip – some fantastic photographs

How to thread a needle easily – fantastic but does it actually work?



Filed under Pick and mix

Skype a Scientist – a great way to invest in the future

I do a lot of outreach or “reach out” as my contract endearingly terms it 🙂 In terms of talks, my outreach spans a great range of ages and experiences; from the University of the 3rd Age (U3A), Women’s Institutes, the Rotary Club and similar organisations, local Natural History Societies, Garden Clubs, and less often, schools and youth groups.  As you can see from the preceding list, most of my ‘formal’ standing in front of an audience and lecturing outreach, although not primarily aimed at the older generation, does most often find them.  Face to face interactions with the younger generation is mainly via University Open Days and events like the Big Bang Fair which are great fun but are annual one-offs. I was thus very pleased when I discovered Skype A Scientist last year and had the chance to extend my ‘face to face’ interactions with the younger generation, not just in the UK but around the world.  My two favourite classroom session were with 9-10 year olds, one class in a primary school in Northern Ireland and the other in an elementary school in Cincinnati.

The questions they asked are wonderful, heartening and stimulating. Some, especially the ‘why’ ones, are pretty hard to answer, remember the ‘language’ we speak as scientists has a vocabulary that is not necessarily the same as that of a 9-year old.  Although I have listed all the questions they asked, I’m not going to post all my attempts at answering them, just some of the ones that weren’t as easy as you might think.  Thankfully, the teachers were kind enough to send me a list of the questions a few days before the session, otherwise I would have been in trouble 🙂  Try answering them yourself and as a side exercise, which questions came from which school?  If you haven’t done Skye A Scientist, I can thoroughly recommend it and hopefully, as a community we can sow enough idea seeds in this age group for a large number to germinate and grow into a high yielding crop of future scientists.

School 1

Do all animals drink water?

Do you mostly work indoors or outdoors?

How did you get interested in your job?

How did you get into your job? Hard work and luck

How long have you been in the insect profession? A long time 🙂

How can you tell poisonous bugs apart from not poisonous bugs? An excellent question as gave me the opportunity to talk about warning colouration and the difference between poisonous and venomous

How does a caterpillar turn into a butterfly? Harder than it seems

How do you get rid of the pests without killing the crops? Gave me the chance to talk about phytotoxicity

How do you remove pesticides without hurting and ruining the food and water? This was actually about organic farming

If you could save any insect from extinction which insect would it be? Really difficult to answer this

Is pesticide the only chemical hurting the plants/insects or is there more? Chance to talk about pollution issues

What is your favourite part in an ecosystem and why?    The insects – because they are cool

What is your favourite consumer?

What is your favourite insect? Had to be an aphid, but then I had to explain what an aphid was 🙂

What is your favourite animal that you have worked with? Large willow aphid of course

What is your favourite animal(s) in the ecosystems you observe? Obviously aphids 🙂

What is the most dangerous insect? Hard to answer, but did give me an opportunity to talk about allergic reactions

What are the most common pests that harm crops? An easy one

What is the coolest animal/insect you have ever seen?   Again, really hard, because there is so much variety, I went for Snow flea, Boreus hiemalis 🙂

What did you want to be when you were a kid? Gerald Durrell 🙂

When did you become a scientist? A long time ago 🙂

Why do insects that have stingers have stingers? One of those why questions!

What’s your favourite animal/insect that you had ever helped? I went for spider just to be controversial

Why did you choose the career of being a college professor in science?

What is your favourite part of your job?  Talking to people about insects

What chemicals have you worked with, and which ones are the most harmful?

What is your favourite insect to learn and inspect? Always aphids 🙂

What kind of animals do you mostly research? Guess what?

What are some tools you use? Told them about pooters

What insect has been infected the most from the chemicals?

Where do you work?

What do you wear for work? What I’m wearing now – jeans and shirt with sleeves rolled up 🙂

What do you think of pesticides?  Gave me a chance to talk about pros and cons and specificity

Why did you chose to be an ecologist? Gerald Durrell

Why do butterflies drink tears from turtle’s eyes? Great chance to talk about puddling and peeing in tropical forests to attract butterflies

You know how there are certain bugs that look the same as other bugs that are poisonous, how does that species that looks the same as the poisonous ones stay not over-populated? Very interesting question and lots to talk about concerning mimicry and aposematism


School 2

Are spiders insects?

Can you heal an ant if it gets sick? Interesting question and gave me a chance to talk about ants helping each other

Do insects sleep at night? Depends on how you define sleep

Do insects hibernate? Some do

Do insects see in black and white or colour? Colour, but generally not red and chance to talk about UV vision

Do slugs have sharp teeth? Depends on what you mean by teeth and sharp

Can leaf cutter ants eat through human skin? Ouch, yes

Can ants swim? Chance to talk about surface tension

How are ants so strong even though they are so small?

How do crickets make the clicking sound?

How many types of insects are there in the world? Lots and a great opportunity to have a rant about vertebrates 🙂

How do butterflies get coloured? Difficult as had to talk about scales, refraction, wavelengths etc

What is a beehive made of?

What is a beetle’s body made of? Easy on the surface but then you have to work out how to describe chitin

What do woodlice eat?

Why are bees so important?  Gave me a chance to talk about how important other pollinators are and how chocolate lovers should love flies 🙂

Why do spiders have so many eyes? Yep!

Why do bees make honey?

Why do dung beetles roll dung? Nice question

Why are bugs so small?  Good opportunity to debunk giant insects in horror films and talk about insect respiratory systems

Why do insects have 6 legs? I went for the descended from organisms with lots of legs and because of size and balance problems, six was the most stable reduction (tripod theory).  Mercifully nobody picked me up about mantids or Nymphalids 🙂

What is the biggest insect? Luckily had a photo to hand


As you can see a bit of a challenge even with advance warning, but definitely worth doing.  School 1 was in the USA and School 2 the UK.  Did you guess correctly?

This year I am looking forward to talking to schools in Moscow and Switzerland; truly global reach.  How cool is that?

1 Comment

Filed under Roundabouts and more, Teaching matters

Ten more papers that shook my world – It pays to move away from home – Janzen (1970) & Connell (1971)

I have long held Dan Janzen in high regard, and not just because he wrote a paper with the memorable title “What are dandelions and aphids?”  (Janzen, 1977).  I have always found his writing enjoyable, and was, and still am, in awe of his ability to straddle whole swathes of ecology, both practically and conceptually. The paper that has, however, had the most impact on me, and perhaps the concept that Janzen is most renowned for, is the one that gave rise to the Janzen-Connell hypothesis/effect (Janzen, 1970).  Janzen was addressing the question of why tropical forests, while generally species rich, have a low density of adult trees of each species when compared with temperate forests (Black et al., 1950).  Janzen states “I believe that a third generalization is possible about tropical tree species as contrasted with temperate ones: for most species of lowland tropical trees, adults do not produce new adults in their immediate vicinity (where most seeds fall).”  He based this statement on his own personal observations, discussions with tropical foresters and on discussions with Joseph Connell.  He then works through several models testing different scenarios, from allelopathy*, different modes of seed dispersal and seed predation. Although allelopathy has been shown to affect seedling recruitment in several tree species (e.g. Webb et al., 1967), his conclusion was that the efficiency of seed/seedling specific predators was the main factor causing the patterns seen in tropical forest structure.  The simple take-home message, and one that I often say to the three of my grown-up sons who still live with us, is that it pays to move away from home; if your parents don’t kill you, then something else will 😊 Easy to remember and understand.

The Janzen model – the further away you are from your parent, the greater the probability that you will survive (Janzen, 1970).

The user-friendly version I use in lectures https://agoutienterprise.files.wordpress.com/2012/09/j-c-diagram1.jpg

So, given that the first mention in print is the Janzen 1970 paper, why is it the Janzen-Connell model/hypothesis/effect and why was a marine biologist,  Joseph Connell, writing about tropical forest diversity (Connell, 1971)?  It could so easily have been a repeat of the Wallace and Darwin contretemps. If you read both papers, it is obvious to see that both men had discusd the subject with each other, and saw their hypothesis as an extension of an earlier paper by the great ecologist, Robert Paine (Paine, 1966).  Connell refers to the Janzen paper as in press, but his ideas saw the light of day in 1970, albeit not analysed fully and referred to as in preparation, at a conference, the proceedings of which did not appear until the following year (Connell, 1971).  The actual data he referred to in his paper, did not appear in journal format until 1984, perhaps one of the longest in preps** ever (Connell et al., 1984).

Although Connell and Janzen continued to address the subject e.g. (Janzen, 1971; Connell, 1978), their names were not linked until Steve Hubbell did so in 1979 (Hubbell, 1979).  This linking of the two names seems to have been the fuse that set off the citation rocket.  As of now, it has been cited over 15 000 times and shows no signs of slowing down.

The Janzen-Connell citation rocket; 15 286 citations to date

So, apart from using it in teaching, how has the Janzen-Connell hypothesis shaken my world? Although I had used the concept in my teaching since the mid-1990s, it was my weekly walk round my 52 sycamore tree transect that got me thinking about it as research topic.  Field work is a great way to keep in touch with your study organism, things go one outside that don’t happen in the lab.  My sycamore transect was set up to monitor the insect herbivores and their natural enemies, but after a few years something else struck me, particularly, during high seed production years (another twenty-year data set for my never going to publish series).  I noticed that although lots of sycamore seedlings emerged underneath my study trees in the spring, by mid-summer hardly any were left; underneath other tree species, they were however, much more common, especially under oak trees.  My first thought was allelopathy, but a quick test using potted sycamore seedling in soil from underneath oak and sycamore trees with standard compost as a control, quickly showed this not to be the case.

Effects of soil type on growth of sycamore seedlings (F = 1.68 2/33 df P =NS).

I then used an undergraduate student assistant (paid I hasten to add) to do a couple of surveys, counting the incidence of sycamore seedlings and saplings underneath different tree species.  This convinced me that there was something going on and I set up twenty permanent plots in 2005, which I monitored until I left Silwood in 2012 (another set of data unlikely to be published), ten under mature sycamore and ten underneath mature oak trees, counting the number of sycamore seedlings that merged every spring and survived or not. After a couple of years I was convinced that there was every possibility of a Janzen-Connell effect going on and persuaded Alex Pigot, then a MSc student that it would be a great project.  To cut a long story short, Alex demonstrated that sycamore seedling survival, was as with tropical tree seedlings, dependent on predation pressure and that this was mainly due to invertebrate herbivores and was greatest underneath their parent trees.

Sycamore seedling mortality highest under sycamore and oak when exposed to invertebrates, vertebrates or both (Pigot & Leather, 2008).

Before anyone accuses me of taking credit for being the first person to demonstrate that the Janzen-Connell effect was also applicable to temperate forests, let me point you at a paper by Douglas Gill (Gill, 1975) who suggested that the spatial patterns of pines and oaks in the New Jersey Pine Barrens might be a result of differential seed predation as suggested by Janzen and Connell.

Despite the undoubted popularity of the Janzen-Connell Hypothesis in ecology, it is still not entirely clear cut; as my colleagues and I pointed out recently “What is clear, is that more studies targeting closed tall forests, and trees from other plant families and their seedlings are urgently needed before we can make sweeping conclusions about the generality of Janzen–Connell effects induced specifically by insects”  (Basett et al., 2019), but nevertheless this is a paper that shook my world and one that is definitely worth reading if you haven’t come across it before or just taken the concept it as gospel.


Basset, Y., Miller, S.E., Gripenberg, S., Ctvrtecka, R., Dahl, C., Leather, S.R. & Didham, R.K. (2019) An entomocentric view of the Janzen–Connell hypothesis. Insect Conservation and Diversity, 12, 1-8.

Black, G.A., Dobzhansky, T. & Pavan, C. (1950) Some attempts to estimate species diversity and population density of trees in Amazonian forests. Botanical Gazette, 111, 413-425.

Connell, J. H. (1971) On the role of natural enemies in preventing competitive exclusion in some marine animals and forest trees.  In: den Boer, P. J. and Gradwell, G. R. (eds), Dynamics of Populations. Centre for Agricultural Publications and Documentation, Wageningen, the Netherlands, pp. 298-312.

Connell, J.H. (1978) Diversity in tropical rain forests and coral reefs.  Science, 199, 1302-1310.

Connell, J.H., Tracey, J.G. & Webb, L.J. (1984) Compensatory recruitment, growth, and mortality as factors maintaining rain forest tree diversity. Ecological Monographs, 54, 141-164.

Gill, D.E.  (1975) Spatial patterning of pines and oaks in the New Jersey Pine Barrens. Journal of Ecology, 63, 291-298.

Hille Ris Lambers, J., Clark, J.S. & Beckage, B. (2002) Density-dependent mortality and the latitudinal gradient in species diversity. Nature, 417, 232-235.

Hubbell, S.P. (1979) Tree dispersion, abundance, and diversity in a tropical dry forest. Science, 203, 1299-1309.

Janzen, D.H. (1970) Herbivores and the numbers of tree species in tropical forests. American Naturalist, 104, 501-528.

Janzen, D.H. (1971) Escape of juvenile Dioclea megacarpa (Leguminosae) vines from predators in a deciduous tropical forest. American Naturalist, 105, 97-112.

Janzen, D.H. (1977) What are dandelions and aphids? American Naturalist, 111, 586-589.

Paine, R.T. (1966) Food web complexity and species diversity.  American Naturalist, 100, 65-75.

Pigot, A.L. & Leather, S.R. (2008) Invertebrate predators drive distance‐dependent patterns of seedling mortality in a temperate tree Acer pseudoplatanus. Oikos, 117, 521-530.

Webb, L.J., Tracey, J.G. & Haydock, K.P. (1967) A factor toxic to seedlings of the same species associated with living roots of the non-gregarious subtropical rain forest tree Grevillea robusta. Journal of Applied Ecology, 4, 13-25.

* the chemical inhibition of one plant (or other organism) by another, due to the release into the environment of substances acting as germination or growth inhibitors

**Let me know if you know of a longer one.  I don’t count Darwin, as he didn’t, as far as I know, actually refer to his theory in print before publication was forced upon him by Wallace.

1 Comment

Filed under Ten Papers That Shook My World

Pick and Mix 26 – more gleanings from around the world

How dinosaurs got their name

It seems that most scientists only have temporary careers 😦

Yes, as we suspected, competitive grant writing is inefficient and wastes scientist’s time

Stephen Heard explains how William Caxton inlfuenced how we report statistics

You don’t need fossil fuels to keep the economy running

Drawing specimens (rather than taking a photograph) is the best way to learn about morphology and taxonomy

Continuing with the botanical theme, plant blindness, yes it is a thing, probably worse than insect blindness which I have written about in the past

Incredible blueness – Ray Cannon on butterfly wings

Electrifying  – flying spiders

Earwig wings – real life origami



Filed under Pick and mix

British Ecological Society Annual Meeting 2018 – representing ecologists but not ecology?

I managed to get to the BES annual meeting this year.  I hadn’t been since 2014 as I boycotted the 2015 meeting*  and the timing of the 2016 and 2017 meetings meant I couldn’t attend those due to teaching commitments.  This time the meeting was in Birmingham and term had ended so there was nothing to get in the way of reconnecting with the annual meetings, the first of which I attended in 1977.  I arrived, soaked to the skin, at the International Conference Centre on a very rainy Sunday afternoon.  Despite the inauspicious start, I was heartened to have a reminder of the BES Undergraduate Summer School; one of my fluorescent beetles from the evening “track a beetle” exercise was on display 😊

Fluorescent carabid beetle, the star of the evening at the Malham BES Summer School 2018

In general, despite the sad memories the pre-Christmas period carries with it, It was good to catch up with old friends and former students.  As a bonus there were some fantastic plenaries; I particularly enjoyed Sam M Gon III’s talk on The Hawaiian Islands as a Model for Biocultural Conservation, which opened with a traditional Hawaiian chant.

A most unusual and very enjoyable plenary

Great to see lots of very special insects

Another great plenary was Danielle Lee’s on science communication and the importance of getting local non-scientists involved in one’s research programmes.

Danielle Lee – On the importance of science communication, a subject close to my heart

There were a lot of great talks, but as is often the case with large meetings, a lot of clashes and hard decisions to make about which talks to miss.  As a member of the Twitterati I was made very aware of this by seeing the Tweets about talks I was missing 😊

Alistair Seddon – a Doctor Who fan

One thing that struck me very forcibly, was that entomology seemed to be very under-represented compared with when I first started attending BES meetings.  There were no specific sessions dedicated to invertebrates; in earlier years it was relatively easy to find insect-themed sessions and talks.  This year, and perhaps this is a modern trend in ecology, even the titles of many of the talks didn’t mention the study organism, the abstract being the only clue about what was being discussed.  I have noticed this trend in paper titles recently too, and will, I am sure, address this in a future blog post 😊 It worries me somewhat that conservation biologists and ecologists have, despite the warnings that a number of eminent ecologists have made in the past, former BES President, Bob May, for example (Clarke & May, 2002) that funding and practical conservation is heavily biased in favour of vertebrate (Seddon et al., 2005), which are hardly representative of global macro-biodiversity. As far as the British Ecological Society goes, one would expect that a Society that has, over the last decade or so, become increasingly politicised, and on the face of it, publicly engaged with climate change and other ecological issues, to actively implement a change in direction of the research supported and showcased.

I have previously taken the Journal of Animal Ecology to task for ignoring most of the world’s animal life, yes you guessed it, invertebrates 😊 Their cover images are similarly biased.  Sadly, I am now going to have to take the British Ecological Society to task. I mentioned earlier that I felt the general content of the talks and posters was not representative of the world we live in and on leaving the conference decided to see if my gut feeling was a true reflection of the event.  Amy Everard of the British Ecological Society, kindly supplied me with the abstracts of the talks and posters which I then categorised according to the study organism(s) covered.  Some were a bit difficult, as even with the abstract it was difficult to decide where the focus was, so fungi and microbes may be a little more under-represented than they were in reality, particularly where the talk was on the interactions between fungi, microbes, insects and plants and in some cases, vertebrates.  I lumped all invertebrates together, although as you might expect, most invertebrates were arthropods and those were mainly insects. Plants included trees and forests where the focus was on the role the plant component played and general includes models and multi-organismal studies.  Vertebrates, which were largely birds and mammals, also includes fish, and the very few studies on amphibians and reptiles. Crude, but I feel it gives the overall picture.

First, just to remind you how life on the planet is divided up between the various taxa based on species described to date (Figure 1).

Figure 1. Relative proportions of plant, animal, fungi and microbial species described to date.

So how does this compare with what attendees at BES2018 saw and heard about? As you can see, my gut was right, the little things that run the world were under-represented in both the talks (Figure 2) and posters (Figure 3).

Figure 2. Taxa represented in talks at BES2018 (plants 32%, vertebrates 25%, invertebrates 20%, general 19%, fungi and microbes 4%)


Figure 3. Taxa represented in posters at BES2018 (plants 34%, vertebrates 31%, invertebrates 15%, general 13%, fungi and microbes 7%).

Of some comfort to plant scientists is that despite the often cited unpopularity of plants among students, about a third of all the talks and posters were plant-based.   If one goes purely by biomass, then this is an under-representation of the importance of plants.  A recent paper (Bar-On et al., 2018), estimates that plants make up almost 90% of the planet’s biomass, with the animal kingdom making up perhaps as little as 5% (Figure 4). Given that insects and other invertebrates account for perhaps 97% of all animal life, this further emphasises that the time and funding given to vertebrate ecology is totally unjustified.

Figure 4. Biomass of organisms on Earth from Bar-On et al (2018)

Unfortunately, the British Ecological Society is not alone in overemphasising the importance of the tiny number of vertebrates.  Perhaps more disturbingly is the fact that references to insects in introductory biology textbooks have declined hugely over the last century (Figure 5) while those to vertebrates have increased (Gangwani & Landin, 2018).

 Disappearing insect references (Gangwani & Landin, 2018).

This is a serious problem and one that the British Ecological Society for one, should be doing something about.  Yes, the BES might represent ecologists in general, but they certainly don’t represent ecology.  The Trustees of the BES should take note of the following statement from a group of ecological entomologists “the neglect of insects as study organisms has led to serious bias in our understanding of the functional ecology of ecosystems” (Basset et al., 2019) and the concerns echoed by conservation practitioners (Figure 6) and if that isn’t enough, then perhaps this will “a broader taxonomic base for threatened species assessments, adequately representing invertebrates, will facilitate more profound conservation and policy decisions” (Eisenhauer et al., 2019).

Figure 6. What people on the ground say; a haphazard selection from Twitter

I’ll just leave you with this thought, there are as many aphid species in the world as there are mammal species, just over 5000, but you wouldn’t know it from the number of PhD and post-doctoral positions that are advertised annually, and as for Tipulids (craneflies), a similar sized family….



Bar-On, Y.M., Philips, R. & Milo, R.  (2018) The biomass distribution on Earth. Proceedings of the National Academy of Sciences, 115, 6506-6511.

Basset, Y., Miller, S.E., Gripenberg, S., Ctvrtecka, R., Dahl, C., Leather, S.R. & Didham, R.K. (2019) An entomocentric view of the Janzen-Connell Hypothesis.  Insect Conservation & Diversity, 12, 1-8.

Clarke, J.A. & May, R.M. (2002) Taxonomic bias in conservation research. Science, 297, 191-192.

Eisenehauer, N, Bonn, A. & Guerra, C.A. (2019) Recognizing the quiet extinction of invertebrates. Nature Communications, 10, 50

Gangwani, K. & Landin, J. (2018) The decline of insect representation in biology textbooks over time. American Entomologist, 64, 252-257.

Seddon, P.J., Soorae, P.S. & Launay, F. (2005) Taxonomic bias in reintroduction projects. Animal Conservation, 8, 51-58.


Filed under Bugbears