Tag Archives: Lepidoptera

Sloth Moths – moving faster than their hosts

One of the minor downsides of our Biology and Taxonomy of Insects module on the MSc course is, that we do have to review a lot of families within some of the groups, Lepidoptera being a prime example.  Current estimates range from 250 000 to 500 000 species in 124 families (Kristensen et al., 2007). Going through the basic biology of each family can be pretty dry stuff, even if I have a personal anecdote or two to help lighten information overload.  I am, for example, able to wax lyrical for several minutes about small ermine moths and their incredible silk-production activities, but even after more than 40 years of playing around with insects I don’t have a personal story for every family of Lepidoptera 🙂 so I am always on the lookout for an extra interesting or mind-blowing fact to help leaven the student’s knowledge diet.

Imagine my delight then when I came across a clip* from a BBC One Wildlife programme, Ingenious Animals, describing an obligate association between sloths and moths and not just because of the rhyming opportunity** 🙂

Sloth with moths – BBC One Ingenious Animals

The earliest record of a moth associated with a sloth that I have been able to find is in 1877 (Westwood, 1877) which merely records that the unidentified moth was “parasitic on the three-toed sloth”. In 1908 a Mr August Busck on a visit to Panama saw a two-toed sloth, Choloepus hoffmanni fall from a tree and noticed several moths flying out of the sloth’s fur.  He caught these and on his return to the United States presented them to Dr Harrison Dyar (Dyar, 1908a).  If the name seems familiar to you that is because Harrison Dyar is better known in connection with Dyar’s Law, the observation that larval growth in arthropods is predictable and follows a geometric progression (Dyar, 1890). The moths were identified by Dyar as a new species which he named Cryptoses choloepi.  Dyar hypothesised that the moths and their larvae lived in the fur of the sloth and it was this that caused the sloth’s matted hair.

Cryptoses choloepi (Lepidoptera, Chrysauginae)


Shortly after publishing the first note Dyar came across two more moth specimens, this time collected from a sloth in Costa Rica.  He felt that these were another species, possibly Bradipodicola hahneli (Dyar, 1908b).  The next mention of a sloth moth that I could fine is in a marvellously titled paper (Tate, 1931) who refers to a moth shot in western Ecuador whose fur was “literally alive with a small species of moth, whose larvae possibly fed on the greenish algae which grew in the hair”.  The idea that sloth moths fed on the fur of living sloths was further reinforced by Brues (1936) although this was not based on any personal observations.  It was only in 1976 that it was discovered that the larvae of the sloth moth Cryptoses choloepi were actually coprophagous (Waage & Montgomery, 1976), the female moths waiting for the three-toes sloth B. infuscatus to descend from the trees to relive their bowels, which they do about once a week.  As an aside, I have known Jeff Waage for many years in his role as a biological control expert but until I discovered this paper about a month ago, had no idea that he had ever spent time inspecting sloth faeces 🙂  Jeff and his co-author Gene Montgomery, described the association between the moths and the sloths as phoretic, rather than parasitic, as they saw no harm being caused to the sloths, but a number of benefits accruing to the moths, namely oviposition-site location being simplified, the fur of the sloth acting as refuge from avian predators and diet enhancement from sloth secretions (Waage, 1980).  It turns out however, that some species of sloth moth do spend their whole life cycle on the sloth, B. hahneli lose their wings once a sloth host is found and their eggs are laid in the fur of the sloth (Greenfield, 1981).  The algae that these moths presumably feed on is considered to be in a symbiotic association with the sloths, providing camouflage and possibly nutrition in the form of trace elements (Gilmore et al., 2001).  Hereby lies a tale.  The two-toed sloths have a much wider diet and home range than three-toed sloths and also defecate from the trees, unlike the three-toed sloths which have a very narrow diet (entirely leaves) and narrow home ranges, yet descend from the relative safety of the forest canopy to defecate, albeit only once a week, but still a risky undertaking (Pauli et al., 2017).  Rather than a phoretic relationship Pauli and colleagues see the relationship between sloths, algae and moths as a three-way mutualism, beautifully summarised in their Figure 3.

Postulated linked mutualisms (þ) among sloths, moths and algae: (a) sloths descend their tree to defecate, and deliver gravid female sloth moths (þ) to oviposition sites in their dung; (b) larval moths are copraphagous and as adults seek sloths in the canopy; (c) moths represent portals for nutrients, and via decomposition and mineralization by detritivores increase inorganic nitrogen levels in sloth fur, which fuels algal (þ) growth, and (d ) sloths (þ) then consume these algae-gardens, presumably to augment their limited diet. This figure brazenly ‘borrowed’ from Pauli et al. 2014).

The sloths take the risk of increased predation by descending to ground level, because by helping the moths they improve their own nutrition and hence their fitness.  Yet another great example of the wonders of the natural world.


Post script

Although not as exotic as the sloth moth, we in the UK can also lay claim to a coprophagous moth, Aglossa pinguinalis, the Large Tabby which feeds on, among other things, sheep dung.  In Spain it is recorded as a cave dweller feeding almost entirely on animal dung, apparently not being too fussy as to the source.



Bradley, J.D. (1982) Two new species of moths (Lepidoptera, Pyralidae, Chrysauginae) associated with the three-toed sloth (Bradypus spp.) in South America.  Acta Amazonica, 12, 649-656.

Brues, C.T. (1936) Aberrant feeding behaviour among insects and its bearing on the development of specialized food habits.  Quarterly Review of Biology, 11, 305-319.

Dyar, H.G. (1890) The number of molts of lepidopterous larvae. Psyche, 5, 420–422.

Dyar, H.G. (1908a) A pyralid inhabiting the fur of the living sloth.  Proceedings of the Entomological Society of Washington, 9, 169-170.

Dyar, H.H. (1908b) A further note on the sloth moth. Proceedings of the Entomological Society of Washington, 10, 81-82.

Dyar, H.G. (1912) More about the sloth moth. Proceedings of the Entomological Society of Washington, 14, 142-144.

Gilmore, D.PP., Da Costa, C.P. & Duarte, D.P.F. (2001) Sloth biology: an update on their physiological ecology, behaviour and role as vectors of arthropods and arboviruses.  Brazilian Journal of Medical and Biological Research, 34, 9-25.

Greenfield, M.D. (1981) Moth sex pheromones: an evolutionary perspective.  The Florida Entomologist, 64, 4-17.

Kristensen, N., Scoble, M.J. & Karsholt, O. (2007)  Lepidoptera phylogeny and systematics: the state of inventorying moth and butterfly diversity.  Zootaxa, 1668, 699-747.

Pauli, J.N., Mendoza, J.E., Steffan, S.A., Carey, C.C., Weimer, P.J. & Peery, M.Z. (2014) A syndrome of mutualism reinfocrs the lifestyle of a sloth.  Proceedings of the Royal Society B, 281, 20133006. http://dx.doi.org/10.1098/rspb.2013.3006.

Pinero, F.S. & Lopez, F.J.P. (1998) Coprophagy in Lepidoptera: observational and experimental evidence in the pyralid moth Aglossa pinguinalisJournal of Zoology London, 244, 357-362.

Tate, G.H.H. (1931) Random observations on habits of South American mammals.  Journal of Mammalogy, 12, 248-256.

Waage, J.K. (1980) Sloth moths and other zoophilous Lepidoptera.  Proceedings of the British Entomological and Natural History Society, 13, 73-74.

Waage, J.K. & Montgomery, G.G. (1976) Crytopses choloepi: a coprophagous moth that lives on a sloth.  Science, 193, 157-158.

Westwood, J.O. (1877) XXVIII. Entomological Notes.  Transactions of the Entomological Society, 25, 431-439.


*For the clip about the sloth moth see here http://www.bbc.co.uk/programmes/p04840xn

**Now, when I see a sloth,

My first thought is for the moth,

That has to make that desperate jump

When the sloth decides to take a dump!




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An inordinate fondness for biodiversity – a visit behind the scenes at the Natural History Museum

Last week  (13th February) I traveled with the MSc Entomology students to the Natural History Museum, London.  As part of their course they are taken behind the scenes and meet some of the curators and their favourite beasts.  This one of my favourite course trips and although I have made the pilgrimage for many years I always find something new to marvel at as well as reacquainting myself with some of my old favourites.  After an early start (0645) we arrived exactly on time (for a change), 10.30, at the Museum site in South Kensington.  I always have mixed feelings about South Kensington, having spent twenty years of my life commuting to Imperial College, just up the road from the museum.  I loved teaching on the Applied Ecology course I ran, but over the years the working atmosphere in the Department became really toxic* and I was extremely glad to move to my present location, Harper Adams University.  After signing in, which with twenty students took some time, Erica McAlister (@flygirl) led us through the thronged galleries (it was half term) to the staff


Nostalgia time, my first biological memory, aged 3.

areas, where the research, identification and curating takes place.  Our first port of call was the Diptera where Erica regaled us with lurid tales of flies, big and small, beneficial and pestiferous.


Erica McAlister extolling the virtues of bot flies


Any one fancy cake for tea?  Kungu cake, made from African gnats


Early advisory poster

As we left to move on to the Hymenopteran, hosted by David Notton, I noticed this classic poster warning against mosquitoes.  David chose bees as the main focus of his part of the tour, which as four of the students will be doing bee-based research projects was very apt.


Admiring the bees

Whilst the students were engrossed with the bees I did a bit of fossicking and was amused to find that tobacco boxes were obviously a preferred choice by Scandinavian Hymenopterists in which to send their specimens to the museum.


Finnish and Swedish tobacco boxes being put to good use

Next was that most eminent of Coleopterists, Max @Coleopterist Barclay who as usual enthralled the students and me, with stories of


Max Barclay demonstrating a Lindgren funnel and talking about ‘fossilised’ dung balls

beetles large and small, anecdotes of Darwin and Wallace and the amusing story of how ancient clay-encased dung balls were for many years thought by anthropologists and archaeologists to be remnants of early humankind’s bolas hunting equipment.  It was only when someone accidentally broke one and found a long-dead dung beetle inside that the truth was revealed 🙂


Often overlooked, the Natural History Museum is an exhibit in itself

 As we were leaving to move on to the Lepidoptera section, I felt obliged to point out to the students that not only is the outside of the museum stunningly beautiful but that the interior is also a work of art in itself, something that a lot of visitors tend to overlook. Once in the Lepidoptera section  Geoff Martin proudly displayed his magnificent collection of Lepidoptera, gaudy and otherwise, including the type specimen of the Queen Alexandra’s Birdwing which was captured with the aid of a shotgun!


Lepidopterist, Geoff Martin, vying with his subjects in colourful appearance 🙂

Lunch and a chance to enjoy the galleries was next on the agenda.  Unfortunately, as it was half term this was easier said than done, although I did find a sunny spot to eat my packed lunch, as a Yorkshireman I always find the prices charged for refreshments by museums somewhat a painful.  In an almost deserted gallery I came across this rather nice picture.


A lovely piece of historical entomological art.

Then it was on to the Spirit Collection.  Erica had laid on a special treat, Oliver Crimmen, fish man extraordinaire.  I may be an entomologist but I can sympathise with this branch of vertebrate zoology.  Fish, like insects are undeservedly ranked below the furries, despite being the most speciose vertebrate group.  I have been in the Spirit Room many times but have never seen inside the giant metal tanks.  Some of these, as Ollie demonstrated with a refreshing disregard for health and safety, are filled with giant fish floating in 70% alcohol.


Fish man, Oliver Crimmen, literally getting to grips with his subjects.


A fantastic end to the day culminated with a group photo with a spectacular set of choppers 🙂

Many thanks to Erica McAlister for hosting and organising our visit and to the NHM staff who passionately attempted to convert the students to their respective ‘pets’.

*one day I will write about it.

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Insects in flight – whatever happened to the splatometer?

I have been musing about extinctions and shifting baselines for a while now; BREXIT and an article by Simon Barnes in the Sunday Times magazine (3rd September 2016) finally prompted me to actually put fingers to keyboard.  I fear that BREXIT will result in even more environmental damage than our successive governments have caused already.  They have done a pretty good job of ignoring environmental issues and scientific advice (badgers) even when ‘hindered’ by what they have considered restrictive European legislation and now that we head into BREXIT with a government not renowned for its care for the environment I become increasing fearful for the environment. Remember who it was who restructured English Nature into the now fairly toothless Natural England, because they didn’t like the advice they were being given and whose government was it who, rather than keep beaches up to Blue Flag standard decided to reclassify long-established resort beaches as not officially designated swimming beaches?  And, just to add this list of atrocities against the environment, we now see our precious ‘green belt’ being attacked.

My generation is liable to wax lyrical about the clouds of butterflies that surrounded us as we played very non PC cowboys and Indians outside with our friends in the glorious sunshine.  We can also fondly reminisce about the hordes of moths that used to commit suicide in the lamp fittings or beat fruitlessly against the sitting room windows at night.  The emptying of the lamp bowl was a weekly ceremony in our house.  We also remember, less fondly, having to earn our pocket-money by cleaning our father’s cars, laboriously scraping the smeared bodies of small flies from windscreens, headlamps and radiator grilles on a Saturday morning.  A few years later as students, those of us lucky enough to own a car, remember the hard to wash away red smears left by the eyes of countless Bibionid (St Mark’s) flies, as they crashed into our windscreens.


Typical Bibionid – note the red eyes; designed specially to make a mess on your windscreen 🙂 https://picasaweb.google.com/lh/photo/GBgoGHhRbj-eUUF9SxZ4s9MTjNZETYmyPJy0liipFm0?feat=embedwebsite

Are these memories real or are we looking back at the past through those rose-tinted glasses that only show the sunny days when we lounged on grassy banks listening to In the Summertime and blank out the days we were confined to the sitting room table playing board games?

We have reliable and robust long-term data sets showing the declines of butterflies and moths over the last half-century or so (Thomas, 2005; Fox, 2013) and stories about this worrying trend attract a lot of media attention. On a less scientific note, I certainly do not find myself sweeping up piles of dead moths from around bedside lamps or extricating them from the many spider webs that decorate our house.  Other charismatic groups, such as the dragonflies and damselflies are also in decline (Clausnitzer et al., 2009) as are the ubiquitous, and equally charismatic ground beetles (carabids) (Brooks et al., 2012).  But what about other insects, are they too on the way out?  A remarkable 42-year data set looking at the invertebrates found in cereal fields in southern England (Ewald et al., 2015) found that of the 26 invertebrate taxa studied less than half showed a decrease in abundance; e.g. spiders, Braconid parasitic wasps, carabid beetles, Tachyporus beetles, Enicmus (scavenger beetles), Cryptophagid fungus beetles, leaf mining flies (Agromyzids), Drosophila, Lonchopteridae (pointed wing flies), and surprisingly, or perhaps not, aphids.  The others showed no consistent patterns although bugs, excluding aphids, increased over the study period.  Cereal fields are of course not a natural habitat and are intensely managed, with various pesticides being applied, so are perhaps not likely to be the most biodiverse or representative habitats to be found in the UK.

But what about the car-smearing insects, the flies, aphids and other flying insects?  Have they declined as dramatically?  My first thought was that I certainly don’t ‘collect’ as many insects on my car as I used to, but is there any concrete evidence to support the idea of a decline in their abundance.  After all, there has been a big change in the shape of cars since the 1970s.


Top row – cars from 1970, including the classic Morris 1000 Traveller that my Dad owned and I had to wash on Saturdays.

Bottom row the cars of today, sleek rounded and all looking the same.


Cars were  much more angular then, than they are now, so perhaps the aerodynamics of today’s cars filter the insects away from the windscreen to safety? But how do you test that?  Then I remembered that the RSPB had once run a survey to address this very point.  Sure enough I found it on the internet, the Big Bug Count 2004, organised by the RSPB.  I was very surprised to find that it happened more than a decade ago, I hadn’t thought it was that long ago, but that is what age does to you 🙂


The “Splatometer” as designed by the RSPB

The idea, which was quite cool, was to get standardised counts of insect impacts on car number platesThe results were thought to be very low as the quote below shows, but on what evidence was this based?

“Using a cardboard counting-grid dubbed the “splatometer”, they recorded 324,814 “splats”, an average of only one squashed insect every five miles. In the summers of 30-odd years ago, car bonnets and windscreens would quickly become encrusted with tiny bodies.”  “Many people were astonished by how few insects they splatted,” the survey’s co-ordinator Richard Bashford, said.

Unfortunately despite the wide reporting in the press at the time, the RSPB did not repeat the exercise.  A great shame, as their Big Garden Birdwatch is very successful and gathers useful data.   So what scientific evidence do we have for a decline in these less charismatic insects?  Almost a hundred years ago, Bibionid flies were regarded as a major pest (Morris, 1921) and forty years ago it was possible to catch almost 70 000 adults in a four week period from one field in southern England (Darcy-Burt & Blackshaw, 1987).   Both these observations suggest that in the past Bibionids were very common.  It is still possible to pluck adult Bibionids out of the air (they are very slow, clumsy fliers) in Spring, but if asked I would definitely say that they are not as common as they were when I was a student.  But as Deming once said, “Without data, you’re just another person with an opinion.”  In the UK we are fortunate that a long-term source of insect data exists, courtesy of Rothamsted Research, the longest running agricultural research station in the world.  Data have been collected from a nationwide network of suction and light traps for more than 50 years (Storkey et al., 2016).   Most of the publications arising from the survey have tended to focus on aphids (Bell et al., 2015) and moths (Conrad et al., 2004), although the traps, do of course, catch many other types of insect (Knowler et al., 2016).  Fortuitously, since I was interested in the Bibionids I came across a paper that dealt with them, and other insects likely to make an impact on cars and splatometers (Shortall et al., 2009).  The only downside of their paper was that they only looked at data from four of the Rothamsted Suction Traps, all from the southern part of the UK, which was a little disappointing.


Location and results of the suction traps analysed by Shortall et al. (2009).

Only three of the trap showed downward trends in insect biomass over the 30 years (1973-2002) analysed of which only the Hereford trap showed a significant decline.  So we are really none the wiser; the two studies that focus on a wider range of insect groups (Shortall et al., 2009; Ewald et al., 2015) do not give us a clear indication of insect decline.   On the other hand, both studies are limited in their geographic coverage; we do not know how representative the results are of the whole country.

What a shame the RSPB stopped collecting ‘splatometer’ data, we would now have a half-decent time series on which to back-up or contradict our memories of those buzzing summers of the past.

Post script

After posting this I came across this paper based on Canadian research which shows that many pollinators, possibly billions are killed by vehicles every year.


Bell, J.R., Alderson, L., Izera, D., Kruger, T., Parker, S., Pickup, J., Shortall, C.R., Taylor, M.S., Verrier, P. & Harrington, R. (2015) Long-term phenological trends, species accumulation rates, aphid traits and climate: five decades of change in migrating aphids.  Journal of Animal Ecology, 84, 21-34.

Brooks, D.R., Bater, J.E., Clark, S.J., Montoth, D.J., Andrews, C., Corbett, S.J., Beaumont, D.A., & Chapman, J.W. (2012) Large carabid beetle declines in a United Kingdom monitoring network increases evidence for a widespread loss of insect biodiversity. Journal of Applied Ecology, 49, 1009-1019.

Clausnitzer, V., Kalkman, V.J., Ram, M., Collen, B., Baillie, J.E.M., Bedjanic, M., Darwall, W.R.T., Dijkstra, K.D.B., Dow, R., Hawking, J., Karube, H., Malikova, E., Paulson, D., Schutte, K., Suhling, F., Villaneuva, R.J., von Ellenrieder, N. & Wilson, K. (2009)  Odonata enter the biodiversity crisis debate: the first global assessment of an insect group.  Biological Conservation, 142, 1864-1869.

Conrad, K.F., Woiwod, I.P., Parsons, M., Fox, R. & Warren, M.S. (2004) Long-term population trends in widespread British moths.  Journal of Insect Conservation, 8, 119-136.

Darcy-Burt, S. & Blackshaw, R.P. (1987) Effects of trap design on catches of grassland Bibionidae (Diptera: Nematocera).  Bulletin of Entomological Research, 77, 309-315.

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.

Fox, R. (2013) The decline of moths in Great Britain: a review of possible causes. Insect Conservation & Diversity, 6, 5-19.

Knowler, J.T., Flint, P.W.H., & Flint, S. (2016) Trichoptera (Caddisflies) caught by the Rothamsted Light Trap at Rowardennan, Loch Lomondside throughout 2009. The Glasgow Naturalist, 26, 35-42.

Morris, H.M. (1921)  The larval and pupal stages of the Bibionidae.  Bulletin of Entomological Research, 12, 221-232.

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.

Storkey, J., MacDonald, A.J., Bell, J.R., Clark, I.M., Gregory, A.S., Hawkins, N. J., Hirsch, P.R., Todman, L.C. & Whitmore, A.P. (2016)  Chapter One – the unique contribution of Rothamsted to ecological research at large temporal scales Advances in Ecological Research, 55, 3-42.

Thomas, J.A. (2005) Monitoring change in the abundance and distribution of insects using butterflies and other indicator groups.  Philosophical Transactions of the Royal Society B, 360, 339-357


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Ideas I had and never followed up

“When I was younger, so much younger than before” I never needed any help to come up with ideas for research topics or papers.   When I was doing my PhD and later as a post-doc, I used to keep a note pad next to my bed so that when I woke up in the middle of night with an idea (which I often did) I could scribble it down and go back to sleep.  (These days sadly, it is my bladder and not ideas that wake me up in the wee small hours 🙂*)

On waking up properly, these ideas, if they still seemed sensible, would  move onto Stage 2, the literature search.  In those days, this was much more difficult than it is now, no Google Scholar or Web of Science then, instead you had to wade though the many hard-copy Abstract series and then get hard copies of the papers of interest.  Once in my hands, either via Inter-library loans or direct from the author, or even photocopied from the journal issue (we did have photocopiers in those days), the papers would be shoved into a handy see-through plastic folder (Stage 3).  Depending on how enthusiastic I was about the idea, I would then either mock-up a paper title page or put the folder in the ‘to deal with later’ pile (Stage 4).   Many of these eventually led on to Stage 5, experiments and published papers.  Others have languished in their folders for twenty or thirty years.

As part of my phased run up to retirement (2021), I have started farming out my long-term publishable (hopefully) data-sets to younger, more statistically astute colleagues and ‘publishing’ less robust, but possibly useful data on my blog site.  I have also, somewhat halfheartedly since the task is monumental, started to go through my old field and lab books that


A monumental collection of data.  The top right picture is my 20-year sycamore data set.  I estimate that there are about 7 million data points in it; of which to date only 1.6 million, give or take a million, are computerised.  I also have a ten-year bird cherry aphid data set from Scotland, waiting to go on the computer, any volunteers?

are not yet computerised.  Whilst doing this I came across some Stage 3 folders, which as you can see from the colour of the paper have languished for some time.


The Forgotten Nine


There were nine forgotten/dismissed proto-papers, the oldest of which, judging by the browning of the paper and my corresponding address, dates from the early 1980s, and is simply titled “What are the costs of reproduction?”.  This appears to have been inspired by a talk given by Graham Bell at a British Ecological Society, Mathematical Ecology Group meeting in 1983.  In case you are wondering, this was one of those meetings supposed to bring theorists and empiricists together.   It didn’t work, neither group felt able to talk to each other 🙂  The idea, inevitably based on aphid data, didn’t bear any fruit, although I do have this graph as a souvenir.  If anyone wants


In those days we used graph paper 🙂

 the data, do let me know.

Slightly later, we find the grandly titled, “Size and phylogeny – factors affecting covariation in the life history traits of aphids”.  This had apparently been worked up from an earlier version of a paper, less grandly, but no less ponderously, titled, “Size and weight: factors affecting the level of reproductive investment in aphids”.  This is based on some basic dissection data from eight aphid species and presents the relationships, or lack of, between adult weight (or surrogate measure), ovariole number, potential fecundity and the number of pigmented embryos.  As far as I can remember these are data that Paul Wellings** and I collected as a follow-up to work we had published from a side project when we were doing our PhDs at the University of East Anglia (Wellings et al., 1980).  The second title was inspired by a paper by Stephen Stearns (Stearns, 1984), who was something of a hero of mine at the time, and was, I guess, an attempt to publish pretty simple data somewhere classier than it deserved 🙂  So this one seems to be a Stage 4, almost Stage 5 idea, and may, if I have time or someone volunteers, actually get published, although I suspect it may only make it to a very minor journal under its original title.

Then we have a real oddity, “Aphids, elephants and oaks: life history strategies re-examined”.  This one as far as I remember, is based on an idea that I had about r- and k-selection being looked at from a human point of view and not the organism’s point of view.  My thesis was that an oak tree was actually r-selected as over its life-time it was more fecund than an aphid 🙂  I suspect this was going to be aimed at the Forum section of Oikos.

The next one, dates from the late-1980s, “Protandry versus protogyny: patterns of occurrence within the Lepidoptera”, and reflects the fact that females of the pine beauty moth, Panolis flammea, on which I was then working, emerge before the males (Leather & Barbour, 1983; Leather, 1984), something not often reported in Lepidoptera.  I wondered what advantage (if any) this gave P. flammea.  I planned this one as a review or forum type paper but never got beyond the title and collecting two references (Robertson, 1987; Zonneveld & Metz, 1991).  I still think this is an interesting idea, but do feel free to have a go yourselves, as again, I suspect that I won’t actually get round to it.

Finishing off my time in Scotland, is a paper simply entitled, “Egg hatch in the bird cherry aphid, Rhopalosiphum padi.” I have ten years of egg hatch data from eight trees waiting to be analysed.  This is almost certainly not worth more than a short note unless I (or a willing volunteer) tie it in with the ten years data on spring and autumn populations on the same trees 🙂 Aphid egg data although not very abundant, is probably not in great demand.  My first published paper (Leather, 1980) was about egg mortality in the bird cherry aphid and 36 years later has only managed to accrue 32 citations, so I guess not an area where one is likely to become famous 🙂

I then have four papers dating from my time as an Associate Member of the NERC Centre for Population Biology at Silwood Park.   The first is titled, “The suitability of British Prunus species as insect host plants” and was definitely inspired by my foray into counting host plant dots as exemplified by the late great Richard Southwood (Leather, 1985, 1986).  I think I was going to look at palatability measures of some sort.

The next is called ‘Realising their full potential: is it important and how many insects achieve it?”  I’m guessing that this was a sort of follow-up to my second most-cited paper ever (Leather, 1988), the story of which you can read here, if at all interested.  Most insects, even those that are pests, die before achieving anywhere near their full reproductive potential, but then so do we humans, and our population continues to grow.  So in answer to the question, I guess not and no it doesn’t matter 🙂

Also linked to insect reproduction is the next paper, which I have followed up with the help of a PhD student, and do hope to submit in the near future, “Queue positions, do they matter”.  As this one may actually see the light of day, I won’t say anything further about it.

And finally, another one about aphid eggs, “Bud burst and egg hatch synchrony in aphids”.  This one was going to be based on my then ten-year sycamore aphid data but is now based on my twenty-year data set and is now in the very capable hands of a PhD student and hopefully will see the light of day next year.

There are also a number of other folders with no titles that are just full of collections of reprints.  I can only guess at what these ideas were so won’t burden you with them.

I mentioned at the beginning of this piece that I don’t wake up in the middle of the night with ideas any more.  As we get older I think there is a tendency to worry that we might run out of ideas, especially when, as we do in the UK, suffer from ludicrously underfunded research councils with very high rejection rates that don’t allow you to resubmit failed grant applications.  It was thus reassuring to see this recent paper that suggests that all is not lost after you hit the grand old age of 30.  That said, I do believe that as you move away from the bench or field, the opportunity to be struck by what you see, does inevitably reduce.  As a PhD student and post-doc you are busy doing whatever it is you do, in my case as an ecological entomologist, counting things, and inevitably you see other things going on within and around your study system, that spark off other ideas.  It was the fear of losing these opportunities as I moved up the academic ladder, which inevitably means, less field and bench time and more time writing grant applications and sitting on committees, that I specifically set aside Monday mornings (very early mornings) to my bird cherry plots and even earlier Thursday mornings to survey my sycamore trees.   Without those sacrosanct mornings I am pretty certain I would have totally lost sight of what is humanly possible to do as a PhD student or post-doc.  This, thankfully for my research group, means that I had, and have, realistic expectations of what their output should be, thus reducing stress levels all round.   As a side benefit I got to go out in the fresh air at least twice a week and do some exercise and at the same time see the wonderful things that were going on around and about my study areas and as a bonus had the chance to get some new ideas.



Leather, S.R. (1984) Factors affecting pupal survival and eclosion in the pine beauty moth, Panolis flammea (D&S). Oecologia, 63, 75-79.

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 host range, plant architecture, age of establishment, taxonomic isolation and species-area relationships. Journal of Animal Ecology, 55, 841-860.

Leather, S.R. (1988) Size, reproductive potential and fecundity in insects: Things aren’t as simple as they seem. Oikos, 51, 386-389.

Leather, S.R. & Barbour, D.A. (1983) The effect of temperature on the emergence of pine beauty moth, Panolis flammea Schiff. Zeitschrift fur Angewandte Entomologie, 96, 445-448.

Robertson, H.G. (1987) Oviposition and site selection in Cactoblastis cactorum (Lepidoptera): constraints and compromises. Oecologia, 73, 601-608.

Stearns, S.C. (1984) The effects of size and phylogeny on patterns of covariation inthe life history traits of lizards and snakes. American Naturalist, 123, 56-72.

Wellings, P.W., Leather , S.R., & Dixon, A.F.G. (1980) Seasonal variation in reproductive potential: a programmed feature of aphid life cycles. Journal of Animal Ecology, 49, 975-985.

Zonneveld, C. & Metz, J.A.J. (1991) Models on butterfly protandry – virgin females are at risk to die. Theoretical  Population Biology, 40, 308-321.


*I hasten to add that I do still have new ideas, they just don’t seem to wake me up any more 🙂

**Now Vice-Chancellor of the University of Wollongong



Filed under Science writing, Uncategorized

Butterflies Galore – visual treats from two very different books


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 🙂


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.).


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!


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.



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



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/


Filed under Book Reviews, EntoNotes

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.



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


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



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)


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.



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.



Filed under Entomological classics, EntoNotes, Ten Papers That Shook My World, Uncategorized

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


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


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.


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.



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



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 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


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.


Filed under EntoNotes

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



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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