Tag Archives: biological control

Weevily clever – on being behaviourally resistant

I am currently sharing my office with a Tupperware container of weevils, Hylobius abietis, the Large pine weevil to be exact.  The reason, just in case you were wondering, is that I have had an undergraduate doing her final year research project with me on ways in which this highly pestiferous weevil might be prevented from feeding on newly planted conifers.  The weevils in my office are those that were left over from her project and being the old softie that I am, and having worked on Hylobius since 1987 I couldn’t bear to throw them away :.)

My office pets – easy to maintain and quite cute

Adult and larvae of Hylobius abietis

You might think that having worked on an insect with the sole aim of trying to reduce its pestiferousness, that I might have succeeded by now.  Say that to the many scientists who have addressed this problem for more than a century and you will be rewarded with the sound of hollow laughter.  The laughter is even hollower if you point them to the statement made by the first UK Forestry Commission entomologist,  J W Munro, who a mere ten years after the formation of the Forestry Commission wrote “The pine weevil (Hylobius abietis) problem still occupies the attention of the Forestry Commissioners” Munro (1929).  Ninety years on I can make exactly the same statement and judging by the global number of papers written about Hylobius, I think I can confidently state that the same can be said for the forest industry as a whole.

Not a problem that is going away! Papers published on Hylobius abietis since 1910.  Data from Google Scholar and Web of Science.

So why is the large pine weevil, or Hylobius as those of us who work on it or attempt to control it, call it so hard to manage? The simple answer is that we have helped it become a pest in the first place and in the second place it has a couple of attributes that give it a bit of an edge. You might even go so far as to say that it is a clever little beast.

First a little bit of history is in order. Up until the beginning of the 20th century references to Hylobius are few and far between, especially in the UK, although there are some German references from the latter half of the 19th Century, a reflection of the fact that the German forest industry was well in advance of that in the UK. Prior to the establishment of conifer plantations, populations of Hylobius would have been small and scattered as the larvae need conifer stumps or large pieces of fallen branch in which to develop.  The adults, which can live for up to four years (Leather et al., 1999), would normally feed on the cambium of thin barked twigs in the upper canopy of conifer trees, and the larvae, depending on how shaded the host stump was, could take from a year to two years to reach adulthood.  The adults are extremely responsive to host volatiles (Nordenhem & Eidmann, 1991) and can locate host plants and egg-laying sites remarkably quickly*.  Plantation forestry with its cycles of clear-fell and subsequent restocking with two year old conifer saplings has been akin to setting up a deliberate breeding programme for Hylobius.  In some cases 100% of all new planting can be destroyed by the adults ring-barking the saplings and on average 30% would be lost if plants were not pre-treated with insecticide.

How to turn an innocuous forest insect into a major pest. Plantation forestry and how it created a forest pest. (Figure adapted from Leather et al, 1999).

Over the years there have been a number of attempts at controlling Hylobius without using insecticides, including cultural methods, physical barriers and biological control using entomopathogenic nematodes (Williams et al., 2013), none of which have been as effective as insecticidal treatment. The latter, although reasonably effective at preventing sapling damage, may not, however, be reducing Hylobius numbers.  This is because Hylobius is, as well as being good at detecting host volatiles, also great at detecting and avoiding insecticides.  A former PhD student of mine, Dan Rose, showed this is in a series of elegant experiments where he manipulated insecticide presence and absence at different scales (Rose et al., 2005).  First he tested if adult Hylobius could detect the presence of an insecticide at a whole plant level, by giving them a choice in semi-field conditions between treated and untreated saplings.  They could, they avoided feeding on treated plants.  Then he gave them a choice of plants where he had sprayed half the canopy with an insecticide, and, yes, you guessed it, they only fed on the untreated parts.

 Given a choice, adult Hylobius abietis will not feed on insecticide treated plants or on those parts of a tree that have been treated with an insecticide

Dan wondered just how good their discriminatory powers were, so using our standard choice boxes,

Standard Hylobius abietis host choice test box

he presented his weevils with pieces of pine twig that had had insecticide painted on to them alternating with equal width untreated stripes, and yes, you guessed, they only ate the untreated parts of the twig.

  Adult Hylobius abietis only fed on the untreated stripes.

Next he sprayed twigs all over, but some with large droplets and some with fine droplets and then gave them the choice between a coarse sprayed twig and a fine sprayed one and as you may have guessed,  they were able tell the difference, and fed on the twigs with the bigger spaces between the droplets of insecticide.

Given a choice between twigs treated with a large droplet spray and a fine droplet spray, adult Hylobius abietis will feed on the twigs with the large droplet size spray application.

 

So this is an indication that adult Hylobius are behaviourally resistant to insecticides, well at least the ones he tested them against. Hylobius are not alone in possessing this trait, other weevils (Haddi et al., 2015) and at least one aphid species (Fray et al., 2014) are also able to detect and avoid insecticide treated substrates.

Hylobius adults are also quite resistant to insecticide poisoning when you force them to eat treated plant material. Some individuals take almost three weeks to die and then if they are removed from the insecticide treated food they soon return to normal.

Figure borrowed from Rose et al.,( 2005)

Remarkable rate of recovery (Figure borrowed from Rose et al., (2006)

 

Hylobius abietis adults are able to recover from pesticides if given the chance, even after a week of exposure.

Given that they are able to recognise and avoid eating treated plant material and if they do, show remarkable powers of recovery, it is very likely that in the field, the reason that the insecticidal treatment works is more to do with repellence than toxicity, so it is unlikely that weevil popualtions are reduced.

To reduce populations rather than divert them elsewhere and given the pressure to remove pesticides from the forest environment, a biological control approach is the logical best option. Entompathogenic nematodes are probably the best option and have received  a lot of attention over the last thirty years or so (Williams et al., 2013), but again Hylobius has a tactic or two up its elytra to make it more difficult to control than other insect pests.  First, like its North American cousin, Hylobius pales (Cornell & Wilson, 1984; Moore, 2001), it can play dead, a phenomenon known as thanatosis or death feigning. In human terms, when they see/feel a nematode approaching, they hold their breath and collapse in a heap. In insect terms, they close their spiracles, the point of entry for the nematodes, and hope that the nematodes give up and go away before they have to breathe again.  If they do have to breathe when the nematodes are still in contact with them then clever old Hylobius is able to brush them away (Ennis et al., 2010). Biological control of adult Hylobius is thus unlikely to be successful, and the larvae and their stump habitats are now the main target of biological control methods (Williams et al., 2013).

Clever, cute and long-lived, what more can you ask for in a pet or should that be pest? 🙂

 

References

Cornell, J.A. & Wilson, L.F.  (1984) Dispersion and seasonal activity of the pales weevil, Hylobius pales (Coleoptera: Curculionidae), in Michigan Christmas tree plantations. Canadian Entomologist, 116, 711-717.

Ennis, D.E., Dillon, A.B. & Griffin, C.T. (2010) Pine weevils modulate defensive behaviour in response to parasites of differing virulence. Animal Behaviour, 80, 283-288.

Fray, L.M., Leather, S.R., Powell, G., Slater, R., McIndoe, E. & Lind, R.J. (2014) Behavioural avoidance and enhanced dispersal in neonicotinoid-resistance Myzus persicae (Sulzer). Pest Management Science, 70, 88-96.

Haddi, K., Mendonça, L.P., Dos Santos, M.F., Guedes, R.N.C & Oliveira, E.E. (2015) Metabolic and behavioral mechanisms of Indoxacarb resistance in Sitophilus zeamais (Coleoptera: Curculionidae). Journal of Economic Entomology, 108, 362-369.

Leather, S.R., Day, K.R. & Salisbury, A.N. (1999) The biology and ecology of the large pine weevil, Hylobius abietis (Coleoptera: Curculionidae): a problem of dispersal? Bulletin of Entomological Research, 89, 3-16.

Moore, R. (2001) Emergence trap developed to capture adult large pine weevil Hylobius abietis (Coleoptera: Curculionidae) and its parasite Bracon hylobii (Hymenoptera: Braconidae). Bulletin of Entomological Research, 91, 109-115.

Munro, J.W. (1929) The biology and control of Hylobius abietis L. Part 2. Forestry, 3, 61-65.

Nordenhem, H. & Eidmann, H.H. (1991) Response of the pine weevil Hylobius abietis L. (Col. Curculionidae) to host volatiles in different phases of its adult life cycle. Journal of Applied Entomology, 112, 353-358.

Nördlander, G., Hellqvist, C., Johansson, K. & Nordenhem, H. (2011) Regeneration of European boreal forests: effectiveness of measures against sedling mortality caused by the pine weevil Hylobius abietis. Forest Ecology and Management, 262, 2354-2363.

Rose, D., Leather, S.R. & Matthews, G.A. (2005) Recognition and avoidance of insecticide-treated Scots pine (Pinus sylvestris) by Hylobius abietis (Coleoptera: Curculionidae): implications for pest management strategies. Agricultural and Forest Entomology, 7, 187-191.

Rose, D.R., Matthews, G.A. & Leather, S.R. (2006) Sub-lethal responses of the large pine weevil, Hylobius abietis, to the pyrethroid insecticide lambda-cyhalothrin. Physiological Entomology, 31, 316-327.

Williams, C.D., Dillon, A.B., Harvey, C.D., Hennessy, R., McNamara, L. & Griffin, C.T. (2013) Control of a major pest of forestry, Hylobius abietis, with enomopathogenic nematodes and fungi using eradicant and prophylactic strategies. Forest Ecology & Management, 305, 212-222.

 

6 Comments

Filed under EntoNotes

Meat eating moths

This post is dedicated with thanks to Entomology Uncensored which gave me the idea for this post.

Unless you believe that the Very Hungry Caterpillar’s diet is truly representative of what a lepidopteran larva eats, you will, if asked, almost certainly answer that caterpillars eat plants and that the adults, if they do feed, do so on nectar. Although this is true for the majority of Lepidoptera, there are a couple of exceptions that have opted for a very different life style. Some of you may already now be saying to yourselves, “Aha what about the clothes moth? That doesn’t eat plants, it eats clothes doesn’t it?”, and you would be right. The larvae of Tinea pellionella, the Case Bearing Clothes Moth, are not plant eaters, they make a living eating wool, fur and feathers among other keratinous* delicacies (Cheema, 1956).

Tinea pellionella – clearly demonstrating why it is called the case-bearing clothes moth

There are some moth species that have gone a step further in adopting an animal-based diet, feeding directly on living animals and not on their cast-off skins and horns. In 1879 the American entomologist John Comstock (1849-1931) while studying a colony of the cottony maple scale Pulvinaria innumerabilis, was one day surprised to find a caterpillar busily eating his study organisms.  Rather than losing his temper and killing the caterpillar, he reared it through to adulthood and realised that this was a species new to science, which he named Dakruma coccidivora (Constock, 1979), now renamed Laetilia coccidivora and recognised as a useful biological control agent (e.g. Goeden et al., 1967; Mifsud, 1997; Cruz-Rodriguez et al., 2016).  Perhaps it had evaded being spotted by less keen-eyed entomologists from its habit of living underneath the scale insects it eats (Howard, 1895).

The hidden life style of Laetilia coccidivora as described by Howard (1895)

Laetilia coccidivora busy eating prickly pear scale insects

Less deadly to its host, but no less of a carnivore, is the moth Epipomponia nawai.  This, and all the other members of its family, thirty-two in total, are all ectoparasites of Hemiptera, especially cicadas and planthoppers (Jeon et al., 2002).  The larvae attach themselves to the abdomen of their host and feed on the juicy flesh underneath the cuticle.  Once ready to pupate they spin a silk thread, drop off their host and spin a cocoon on the bark of the tree their host has fed on (Liu et al., 2018).  The adults do not fed and only live long enough to mate and lay eggs.  For those of you who love a mystery, no-one knows how the moth larvae find their cicada hosts. One possibility is that they might use the cicada song as a cue but this has, so far, not been proven (Liu et al., 2018).

Larva of Epipomponia nawai parasitizing an adult cicada (Liu et al., 2018).

An even more striking example of predatory behaviour in moth larvae is that shown by members of an otherwise herbivorous Genus of Geometrid (looper) moths, Eupithecia.  The Eupithecia have a worldwide distribution, but in Hawaii, all but two of the species are ambush predators Montgomery, 1983).  The caterpillars show typical looper behaviour, remaining motionless pretending to be a twig or leaf, depending on their colour.  When a potential prey item bumps into the back of the caterpillar it rears backwards and catches the victim between its elongated and spiny thoracic legs and then chomps happily on its juicy meal.  It is thought that the absence of praying mantises on the Hawaiian Islands allowed the ancestors of the original Eupithecia that colonised the islands to fill their empty niche (Montgomery, 1983; Mironov, 2014).  The caterpillars are not fussy about what they eat, as long as they can grab and keep hold of it and it doesn’t fight back.  They have been recorded as eating flies, braconid wasps, leafhoppers, other Lepidopteran larvae, crickets and even spiders and ants (Montgomery, 1983, Sugiura, 2010).

Eupithecia orichloris attacking and eating an ant (Sugiura 2010)

Last in my list of carnivorous Lepidoptera and perhaps the most surprising are the Vampire Moths.  The phenomenon of “puddling” by butterflies to obtain sodium is well-known (e.g. Boggs & Jackson, 1991) and can be a very attractive sight.

A sight to enjoy – mud puddling https://www.earthtouchnews.com/in-the-field/backyard-wildlife/mud-puddling-the-butterflys-dirty-little-secret/

Somewhat less attractive behaviour is seen in a number of moth species from the Noctuid, Geometrid and Pyralid families which satisfy their desire for Sodium by feeding as adults from the tears and pus of mammals, including humans (Bänziger & Büttiker, 1969).

The Noctuid moth Lobocraspis griseifusa sucking lachrymal fluid (tears) from a human’s eye.  The author, whose eye this is, rather gruesomely asks us to “note the deep penetration of the proboscis between eye and eye lid” Bänziger & Büttiker (1969).

Some Noctuid moths have taken this a step further, perhaps a step too far. Moths of the Genus Calyptra, have very strong proboscises which allow them to feed through the skin of fruit, even oranges, hence their common name, fruit-piecing moths.  A few species however, have adopted a somewhat more interesting diet and have developed a taste for fresh mammalian blood, again, including that of humans, which they suck directly from their victims (Bänziger, 1968).  They are, of course, known as the Vampire Moths!

Calyptra thalictri Vampire Moth in action – note the barbed proboscis

Happy Halloween!

References

Bänziger, H. (1968) Prelimnary observations on a skin-piercing blood-sucking moth (Calyptra eustrigata) (Hmps.) (Lep., Noctuidae)) in Malaya.  Bulletin of Entomological Research, 58, 159-165.

Bänziger, H. & Büttiker, W. (1969) Records of eye-frequenting Lepidoptera from man. Journal of Medical Entomology, 6, 53-58.

Boggs, C.L. & Jackson, L.A. (1991) Mud puddling by butterflies is not a simple matter. Ecological Entomology, 16, 123-127.

Cheema, P.S. (1956) Studies on the Bionomics of the Case-bearing Clothes Moth, Tinea pellionella(L.). Bulletin of Entomological Research, 47, 167-182.

Comstock, J.H. (1879) On a new predaceous Lepidopterous insects.  The North American Entomologist, 1, 25-30.

Cruz-Rodriguez, J.A., Gonzalez-Machoro, E., Gonzales, A.A.V., Ramirez, M.L.R. & Lara, F.M. 92016) Autonomous biological control of Dactylopius opuntia (Hemiptera: Dactlyliiopidae) in a prickly pear plantation with ecological management.  Environmental Entomology, 45, 642-648.

Goeden, R.D., Fleschner, C.A. & Ricker, D.W. (1967) Biological control of prickly pear cacti on Santa Cruz Island, California. Hilgardia, 38, 579-606.

Howard, L.O. (1895) An injurious parasite.  Insect Life, 7, 402-404.

Jeon, J.B., Kim, B.T., Tripotin, P. & Kim, J.I. (2002) Notes on a cicada parasitic moth in Korea (Lepidoptera: Epipyropidae). Korean Journal of Entomology, 32, 239-241.

Liu, Y., Yang, Z., Zhang, G., Yi, Q. & Wei, C. (2018) Cicada parasitic moths from China (Lepidoptera: Epipyropidae): morphology, identity, biology, and biogeography.  Systematics & Biodiversity, 16, 417-427.

Mifsud, D. (1997) Biological control in the Maltese Island – past initaitives and future programmes.  Bulletin OEPP/EPPO Bulletin, 27, 77-84.

Mironov, V.G. (2014) Geometrid moths of the Genus Eupithecia Curtis, 1825 (Lepidoptera, geometridae): prerequisites and characteristic features of high species diversity. Entomological Review, 94, 105-127.

Montgomery, S.L. (1983) Carnivorous caterpillars: the behaviour, biogeography and conservation of Eupithecia (Lepidoptera: Geometridae) in the Hawaiian Islands. GeoJournal, 7, 549-556.

Sugiura, S. (2010) Can Hawaiian carnivorous caterpillars attack invasive ants or vice versa? Nature Precedings

Leave a comment

Filed under EntoNotes

Inspiring and being inspired by the next generation – Crop Protection Summer School – CROPSS 2018

Last year I wrote about my BBSRC funded Crop Protection Summer School, CROPSS and how pleased I was with the positive response of the students to working in, what to them, was a totally novel subject area.

Like last year, the Summer School started on Sunday afternoon, with an introduction from me about why crop protection was important and how Integrated Pest Management is all about ecology, NOT spraying and eradication, something I have been banging on about for many years and which needs to be reiterated again and again, so here I am reiterating it yet again 😊.

We then had an excellent dinner at our local pub, The Lamb Inn, and continued with an outdoor Pub Quiz.

Food, drink and a quiz – perfect for a sunny Sunday evening

To make things easier for the Quiz Master, me, the quiz was all picture rounds.  The first round was all about charismatic megafauna (almost all answered correctly), then common British wild flowers (about 60% correct), common British trees (50% correct), common British insects (30% correct), I think you can see where I am going with this😊 Catering for the rest of the week was in our excellent campus refectory and as last year, the students were all very complimentary about the quality and quantity of the food and the choices available.

As with last year we had specific days allocated to the main crop protection areas; agronomy, entomology, nematology, plant pathology, weed science and spray technology.  In the evenings we had a speaker from ‘industry’; Dr Lucy Broom, a former student of mine who works at OxitecRob Farrow from Syngenta, David George from Stockbridge Technology Centre, Nicola Spence the Chief Plant Health Officer and Neal Ward from BioBest.  They were all very well received and had to answer a lot of interesting and very well formulated questions, both in the classroom and in the Student Union Bar afterwards.

I am certain that I speak for us all, when I say the students and staff involved found it a very rewarding week.  The weather was glorious as you can see from the photographs, which I will, in time honoured tradition, let tell the story.

Heigh ho, heigh ho it’s off to sample we go

Entomology in action – sweep nets and Pooters

Glorious weather,  just right for looking at light trap catches with Heather Campbell and suction sampling with Andy Cherrill

 

Looking for weeds in the cereal variety trials with John Reade

Labs and classroom

Darts in the bar and chasing fluorescent beetles in the dark

 

The students loved the course and we loved their enthusiasm and commitment.

I should have taken this picture when we are all there 🙂

And, finally, Just to remind you why we need a well-trained and youthful cadre of crop protection scientists.

 

 

3 Comments

Filed under Teaching matters

Not all aphids grow up to be aphids – the enemy within

It has been said that if aphids had their own way and unlimited resources the world as we know it would be 149 km deep in the cute little beasts (Harrington, 1994 ). Last year I wrote about how predators that feed on aphids, although useful, don’t really cut the mustard when it comes to keeping them in check and suggested that their host plants played a major role in keeping aphids from taking over the World.  While they do play an important part in keeping aphid populations under control, and are aided and abetted by aphid specific predators, there are, however, some much more efficient aphid-specific natural enemies out there.  They may be less conspicuous than the brightly coloured ladybirds that we often see munching their way through aphid colonies; public perception of their name may make people wince, but these beautiful and graceful creatures make sure that our appetite for salads and exotic vegetables out of season is satisfied safely and efficiently.  Their life cycles rival that of their prey, or should that be hosts, and entomologists fondly imagine that the film Alien was inspired by them 😊

I am, of course, talking about parasitic wasps, or parasitoids as they are more commonly known.  They are called parasitoids because unlike true parasites which generally speaking keep their hosts alive, insect victims of these wasps will, if successfully parasitized, die well before their non-parasitized relatives. In case you were wondering, the term parasitoid was coined by the Finnish Hemipterist, Odo Reuter (1913).  Aphids are not the only insects that are attacked by parasitoid wasps. The action of insect parasites has been known about for over two hundred years.  Erasmus Darwin, grandfather of the more famous Charles, noted that Ichneumonid wasps parasitised cabbage white butterfly caterpillars and so should be encouraged by gardeners (Darwin, 1800).  This is not the only early mention of parasitic insects in this context; Wheeler (1928), points out that back in the 1850s, two Italian entomologists, Camillo Rondani and Vittore Ghiliana also suggested the use of parasitic insects as biological control agents.  Aphid pests of glasshouse crops originally controlled mainly by predators (van Lenteren & Woets, 1988) are now routinely controlled by the application of commercially produced Braconid and Chalcid wasps (Boivin et al., 2012; van Lenteren, 2012).

Three commonly used aphid parasitoid biological control agents in action. Images from http://biologicalservices.com.au/products/aphelinus-2.html and https://www6.inra.fr/encyclopedie-pucerons/Especes/Parasitoides/Braconidae-Aphidiinae/Praon-volucre

When people think of Hymenoptera, they tend to think of bees, Vespid wasps and ants as being the most important and abundant.  They are very much mistaken.  The Parastica, or parasitoid wasps, are, by a huge margin, the most speciose and abundant section of

Parasitoids clearly dominate the Hymenopteran fauna of the British Isles (Many thanks to Natalie Dale-Skey of the NHM for permission to use this).

the Hymenoptera both in the UK and elsewhere

In the tropics the parasitoids are even more dominant. Data from Gaston et al., (1996).

Once parasitized, the egg(s), unless they are encapsulated by the aphid ‘immune’ system, hatch and begin to feed on the internal tissues of their, presumably, unsuspecting aphid host.  The parasitoid larvae avoid feeding on vital parts of the aphid, so that it can continue to grow and develop and provide food for the parasitoid, until the parasitoid is ready to pupate. Once the parasitoid is ready to pupate it delivers the coup de grace putting the aphid out of its misery and allowing the formation of the ‘mummy’ in

The three most common types of aphid mummies.  Images from http://resources.rothamsted.ac.uk/science-stories/aphids-mummies-and-cadavershttp://biologicalservices.com.au/products/aphelinus-2.html and https://farm1.static.flickr.com/327/18532751584_becc0e56e9_b.jpg respectively.

which the parasitoid completes its development before sawing its way out to emerge as a winged adult ready to seek out new hosts, leaving a characteristic neat circular hole in mummy case. In case you were wondering why the mummy of Praon volucre looks like it is sitting on a plate, this because, unlike the other aphid parasitoids, the final instar cuts its way out of the bottom of the aphid and spins its cocoon externally underneath the remnants of the aphid, hence the ‘plate’ (Beirne, 1942).

And out she comes; emerging parasitoid – http://resources.rothamsted.ac.uk/science-stories/aphids-mummies-and-cadavers

 

Lysiphelbus testaceipes  Photo by J.K.Clark, University of California Statewide IPM Project

Once an aphid, now a hollow mummy; note the neat emergence holes.  Aphid parasitoids are very much tidier than the parasitic lifeform in the classic film Alien 🙂

Another aspect of their life style that makes parasitoids a breed apart from true parasites, is that as well as using aphids as egg laying sites for their larvae, the adults like to snack on them every now and then to help mature more eggs and to keep up their energy levels; sometimes quaintly described as predatism (Flanders, 1953).  Although the parasitoids can make feeding attacks at any time, they appear to feed first and then start laying their eggs (e.g. Collins et al., 1981).

Parasitoids are widely used as biological control agents in glasshouses and other protected environments as they are generally regarded as being more effective than predators (Debach & Rosen, 1991), although there is some support that generalist predators can play a significant part in biological control in the wider environment (Symondson et al., 2002; Gontijo et al., 2015).  That said, aphid parasitoids seem to be fairly host specific in that commercial companies offer specific parasitoid mixtures to control different aphid pest species e.g.  https://www.koppert.com/pests/aphids/product-against/aphipar/ [Note this is NOT an endorsement]. In fact it has been suggested that the relationship between aphids and their parasitoids can be used to clarify aphid taxonomic relationships (Mackauer, 1965). On the other hand, there are very few examples of monophagous aphid parasitoids, most being described as oligophagous (Stary & Rejmanek, 1981).   So given that there is a fair bit of evidence that the parasitoids attacking aphids do show some discrimination in their choice of hosts, how do they find them?

Parasitoids in general were originally thought to be “possessed of an unerring instinct that guided them in their search for hosts” but Cushman (1926) rebutted this idea pointing out that actually the parasitoids first home in on the habitat or food plant that their host lives in and then search for their host (Laing, 1937).   The parasitoids referred to by Cushman and Laing, are however, not parasitoids of aphids, attacking lepidopteran leaf miners and carrion feeding flies respectively, so you might perhaps think that aphid parasitoids could have a different strategy. Although habitat selection by parasitoids of lepidopteran larvae (Thorpe & Caudle, 1938) and sawfly larvae (Monteith, 1955), using olfactory cues of their host’s food plant was confirmed readily easily and early on, the situation with aphids was less clear cut. Manfred Mackauer for example, suggested that aphid parasitoids might be using visual cues, such as leaf deformities or damage to find their aphids hosts (Mackauer, 1965).  The breakthrough came when three cabbage loving entomologists from the USA used an olfactometer to first show that the Braconid parasitoid Diaeretiella rapae, responded positively to the odour of collards (what we in the UK call spring greens) and second to show a very strong preference for them to lay their eggs in the aphid Myzus persicae when it was feeding on crucifers rather than other host plants.  They attributed this to the presence of mustard oil, the chemical that gives cabbages their distinctive taste and suggested that once the aphid host plant was found then the parasitoids used visual cues to find their aphid victims (Read et al., 1970).  Six years later it was firmly established that parasitoids in general used olfactory cues both to locate the habitat of their host (long-range) and then a short-range to find and confirm the identity (contact chemicals) their insect hosts (Vinson, 1976).

It was thought that the aphid parasitoids were chemically ‘conditioned’ during their larval life within the aphid feeding on a host plant and that this influenced their adult host preferences (e.g. Sheehan & Shelton, 1989; Wickremasinghe & Van Emden, 1992).  These, and other similar results, seemed to support the Hopkins host selection principle (Hopkins, 1917) which states that adult preferences are learnt as larvae.  A very neat experiment by van Emden et al., (1996) proved this hypothesis wrong. They transferred aphid mummies from the plant on which they had been parasitized on to another host plant and this changed the preference of the emerging adult, seeming to suggest that this was how aphid parasitoids developed their host preferences.  Now comes the neat, and very tricky part; if however, the parasitoid pupae were removed (very carefully) from the mummy case and reared to adulthood in the absence of a host plant or mummy and kept in a glass tube, the emerging adults showed no preference for particular host plants, clearly showing that adult preferences were  not determined during larval development but ‘conditioned’ by exposure to the external skin of the aphid mummy on emergence (van Emden et al., 1996).  Using aphids reared on an artificial diet (Douloumpaka & van Emden, 2003) showed that the it was very likely that the mother parasitoid leaves a chemical cue in or around the egg(s) she lays and that this is later incorporated into the silk of the parasitoid pupa, thus inducing the host preference seen as an adult.

An additional twist to the story is that male and female parasitoids differ in their responses to odours.  Both sexes of Aphidius uzbekistanicus and A. ervi, parasitoids of cereal aphids in the UK, respond to plant odours, but only females respond to aphids (Powell & Zhi-Li, 1983).  Males of both species are, however, attracted to the odours of their respective females, suggesting the existence of a sex pheromone. The existence of a sex pheromone in aphid parasitoids had been suggested a few years earlier when it was shown that male D. rapae attempted to copulate with filter paper that had had female abdomens crushed on them (Askari & Alisha, 1979).  The existence of sex pheromones in aphid parasitoids has now been shown in several species (e.g. Decker et al., 1993; McNeil & Broduer, 1995).  Strangely, female parasitoids also respond to sex pheromones, but in their case, the sex pheromones of aphids.  It turns out that they ‘parasitise’ aphids in more than one way, they home in on their prey using the aphid sex pheromone and this enables them to find a suitable overwintering host (Hardie et al., 1991).  At other times of the year they also use other aphid indicators; several studies have shown that parasitoids use the presence of aphid honeydew to help them find their hosts (Budenberg, 1990; Bouchard & Cloutier, 1984; Gardner & Dixon, 1985).

Predators of aphids such as ladybirds use chemical markers to warn other ladybirds that they have laid eggs near aphid colonies, thus reducing the chances of cannibalism and competition (e.g. Oliver et al., 2006). Given that the eggs of aphid parasitoids are laid internally, they are in effect invisible, it would make sense if the parasitoids ‘marked’ their hosts in some way to avoid other parasitoids laying their eggs in an already parasitized aphid, superparasitism.  Sure enough, there is some evidence that some adult parasitoids can recognise aphids that already have larval parasitoids developing inside them although they don’t seem to be able to consistently recognise already parasitized aphids until some hours afterward (e.g. Cloutier et al., 1984).  In some cases, it seems that it is the aphid herself that prevents superparasitism by reacting more aggressively towards parasitoids after being attacked once (Gardner & Dixon, 1984) and also by the presence of dried siphuncular secretions on the aphid’s skin (Outreman et al., 2001).  The waxy secretion had an effect for up to a day or so after which the internal changes caused by the developing parasitoid larvae were enough to deter further oviposition attempts.

It is a good thing for the poor aphids that they have such a high reproductive rate, or they would truly be in dire straits.  On the other hand, as exemplified by the words of Jonathan Swift (1733),

“So naturalists observe, a flea
Has smaller fleas that on him prey;
And these have smaller still to bite ’em,
And so proceed ad infinitum

there are parasites of parasitoids, the hyperparasites, that help keep the numbers of parasitoids under control, and thus, indirectly, help aphids remain relatively abundant.

 

References

Askari, A. & Alisha, A. (1979) Courtship behavior and evidence for a sex pheromone in Diaeretiella rapae (Hymenoptera: Braconidae), the cabbage aphid primary parasitoid. Annals of the Entomological Society of America, 72, 79-750.

Beirne, B.P. (1942) Observations on the life-history of Praon volucre Haliday (Hym.: Braconidae), a parasite of the mealy plum aphis (Hyalopterus arundinis Fab.). Proceedings of the Royal Entomological Society of London, Series A, General Entomology, 17, 42-47.

Boivin, G., Hance, T. & Brodeur, J. (2012) Aphid parasitoids in biological control.  Canadian Journal of Plant Science, 92, 1-12.

Bouchard, Y. & Cloutier, C. (1984) Honeydew as a source of host-searching kairomones for the aphid parasitoid, Aphidius nigripes (Hymenoptera: Aphidiidae).  Canadian Journal of Zoology, 62, 1513-1520.

Budenberg, W.J. (1990) Honeydew as a contact kairomone for aphid parasitoidsEntomologia experimentalis et applicata, 55, 139-148.

Cloutier, C., Dohse, L.A. & Bauduin, F. (1984) Host discrimination in the aphid parasitoid Aphidius nigripes. Canadian Journal of Zoology, 62, 1367-1372.

Collins, M.D., Ward, S.A., & Dixon, A.F.G. (1981) Handling time and the functional response of Aphelinus thomsoni, a predator and parasite of the. Journal of Animal Ecology, 50, 479-487.

Cushman, R.A. (1926) Location of individual hosts versus systematic relation of hots species as a determining factor in parasitic attack. Proceedings of the Entomological Society of Washington, 28, 5-6.

Darwin, E. (1800) Phytologia: or The Philosophy of Agriculture and Gardening. P. Byrne, Grafton Street, London.

Debach, P. & Rosen, D. (1991) Biological Control by Natural Enemies, Cambridge University Press, New York.

Decker, U.M., Powell, W. & Clark, S.J. (1993) Sex pheromone in the cereal aphid parasitoids Praon volucre and Aphidius rhopalosiphiEntomologia experimentalis et applicata, 69, 33-39.

Douloumpaka, S. & van Emden, H.F. (2003) A maternal influence on the conditioning to plant cues of Aphidius colemani Viereck, parasitizing the aphid Mysuze persicae SulzerPhysiological Entomology, 28, 108-113.

Flanders, S.E. (1953) Predation by the adult Hymenopteran parasite and its role in biological control. Journal of Economic Entomology, 46, 541-544.

Gardner, S.M. & Dixon, A.F.G. (1984) Limitation of superparasitism by Aphidius rhopalosiphi: a consequence of aphid defensive behaviour. Ecological Entomology, 9, 149-155.

Gardner, S.M & Dixon, A.F.G. (1985) Plant structure and foraging success of Aphidius rhopalosiphi (Hymenoptera: Aphidiidae).  Ecological Entomology, 10, 171-179.

Gaston, K.J., Gauld, I.D. & Hanson, P. (1996) The size and composition of the hymenopteran fauna of Costa Rica.  Journal of Biogeography, 23, 105-113.

Griffiths, D.C. (1960) The behaviour and specificity of Monoctonus paldum Marshall (Hym., Braconidae), a parasite of Nasonovia ribis-nigbi (Mosley) on lettuce. Bulletin of Entomological Research, 51, 303-319.

Hardie, J., Nottingham, S.F., Powell, W. & Wadhams, L.J. (1991) Synthetic aphid sex pheromone lures female parasitoids.  Entomologia experimentalis et applciata, 61, 97-99.

Harrington, R. (1994) Aphid layer. Antenna18, 50-51.

Hopkins, A.D. (1917) Contribution to discussion.  Journal of Economic Entomology, 10, 92-93.

Holler, C. (1991) Evidence for the existence of a species closely related to the cereal aphid parasitoid Aphidius rhopalosiphi De Stefani-Perez based on host ranges, morphological characters, isoelectric focusing banding patterns, cross-breeding experiments and sex pheromone specificities (Hymenoptera, Braconidae, Aphidiinae. Systematic Entomology, 16, 15-28.

http://www.biologicalcontrol.info/aphid-primary-and-hyperparasitoids.html

Laing, J. (1937) Host-finding byinsect parasites 1. Observations on the finding of hosts by Alysia manducator, Mormoniella vitripennis and Trichogramma evanescensJournal of Animal Ecology, 6, 298-317.

Mackauer, M. (1965) Parasitological data as an aid in aphid classification. Canadian Entomologist, 97, 1016-1024.

McNeil, J.N. & Brodeur, J. (1995) Pheromone-mediated mating in the aphid parasitoid, Aphidius nigripesJournal of Chemical Ecology, 21, 959-972.

Monteith, L.G. (1955) Host preferences of Drino bohemica Mesn. (Diptera; Tachnidae) with particular reference to olfactory responses.  Canadian Entomologist, 87, 509-530.

Oliver, T.H., Timms, J.E.L., Taylor, A. & Leather, S.R. (2006) Oviposition responses to patch quality in the larch ladybird Aphidecta obliterata (Coleoptera: Coccinellidae): effects of aphid density, and con- and heterospecific tracks. Bulletin of Entomological Research, 96, 25-34.

Outreman, Y., Le Ralec, A., Plantegenest, M., Chaubet, B, & Pierre, J.S. (2001) Superparasitism limitation in an aphid parasitoid: cornicle secretion avoidance and host discrimination ability. Journal of Insect Physiology, 47, 339-348.

Powell, W. & Zhi-Li, Z. (1983) The reactions of two cereal aphid parasitoids, Aphidius uzbekistanicus and A. ervi to host aphids and their food-plants.  Physiological Entomology, 8, 439-443.

Reuter, O.M. (1913). Lebensgewohnheiten und Instinkte der Insekten (Berlin: Friendlander).

Stary, P. & Rejmanek, M. (1981) Number of parasitoids per host in different systematic groups of aphids: The implications for introduction strategy in biological control (Homoptera: Aphidoidea; Hymenoptera: Aphidiidae). Entomologica Scandinavica, Suppl. 15, 341-351.

Riley, W.A. (1931) Erasmus Darwin and the biologic* control of insects. Science, 73, 475-476.

Sheehan, W. & Shelton, A.M. (1989) The role of experience in plant foraging by the aphid parasitoid Diaeretiella rapae (Hymenoptera: Aphidiidae).  Journal of Insect Behavior, 2, 743-759.

Symondson, W.O.C., Sunderland, K.D., & Greenstone, M.H. (2002) Can generalist predators be effective bicontrol agents? Annual Review of Entomology, 47, 561-594.

Thompson, W.R. (1930) The principles of biological control. Annals of Applied Biology, 17, 306-338.

Thorpe, W.H. & Caudle, H.B. (1938) A study of the olfactory responses of insect parasites to the food plant of their host.  Parasitology, 30, 523-528.

Van Emden, H.F., Spongal, B., Wagner, E., Baker, T., Ganguly, S. & Douloumpaka, S. (1996) Hopkins’ ‘host selection principle’, another nail in its coffin.  Physiological Entomology, 21, 325-328.

Van Lenteren, J.C. (2012) The state of commercial augmentative biological control: plenty of natural enemies, but a frustrating lack of uptake. BioControl, 57, 1-20.

Van Lenteren, J.C. & Woets, J. (1988) Biological and integrated control in greenhouses.  Annual Review of Entomology, 33, 239-269.

Vinson, S.B. (1976) Host selection by insect parasitoids.  Annual Review of Entomology, 21, 109-133.

Wheeler, W.M. (1922). Social life among the insects: Lecture II. Wasps solitary and social. Scientific Monthly, 15, 68-88.

Wheeler, W.M. (1928) Foibles of Insects and Men.  Alfred Knopf, New York

Wickremasinghe, M.G.V. & Van Emden, H.F. (1992) Reactions of adult female parasitoids, particularly Aphidius rhopalosiphi, to volatile chemical cues from the host plants of their aphid prey. Physiological Entomology, 17, 207-304.

*This is how he spelt it; not a mistake on my part J

2 Comments

Filed under Aphidology, Aphids

Pick and mix 5 – more links to ponder

Another set of links that interested me enough to read (and this week, watch) them all the way through.

 

Interesting (tongue-in-cheek) post about using Ribwort plantain as a garden flower

Jo Cartmell (@watervole) on how to turn your boring lawn into a beautiful wildflower meadow

Gretchen Vögel asks – Where have all the insects gone?

How ploughing and deep tillage methods are harming earthworms worldwide

We have been telling our students for years that one of the advantages of biological control compared with conventional use of pesticides is that prey are unlikely to evolve resistance to natural enemies.  Well, we were wrong – here is a story about a pest weevil that has done just that  – unfortunately behind a pay wall

Insects and ethics – Some very interesting points, but as much as I love insects which I do passionately, I am very happy, that ethically speaking, they are not classified as animals. Research would be impossible. That said, all insects in my garden live a free and happy life and are never knowingly killed, not even if they are on my bean plants 🙂

A nice article about photographing spiders and also mentions ethics

Here Markus Eichhorn writes about the questionable ethical standpoints of some otherwise reputable scientists from the last century

An interactive blog post about global crop diversity and eating habits – quite revealing, try it and see

An interesting and well produced short video that could be useful if you want to explain how sustainable management of tropical forests helps the planet and why you should only buy FSC certified products

 

Leave a comment

Filed under Pick and mix

Ten papers that shook my world – Solomon (1949) – quantifying predator efficiency

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

 

According to Google Scholar there are 1149 (only 773 in 2013)citations to this paper, an average of 17.1 citations per year, compared with the 12.5 I reported back in 2013.  Although influential, it had a slow start, only 383 citations being recorded for it between 1949 and 1993. Since 2000 it has averaged about 48 citations a year (760 in total), 225 of those since 2013.** To the modern reader this paper comes across as wordy and discursive, more like a popular article than a scientific paper. This does not, however, mean that the science and the man behind the article were not first class. Journals had less pressure on their space in those days and scientists had more time to think and read. If only it were so now. Despite the relatively low number of citations, this paper has had an immense influence on the study of population dynamics, although I will have to confess, that for my generation who were undergraduates in the 1970s, Solomon’s little Study in Biology*** book, Population Dynamics, published in 1969, was our main, if not only, encounter with his work.

Solomon 1

Making sure that nobody could claim my copy of Population Dynamics

Solomon terms

Here Solomon introduces the term functional as in a density related response

Nowadays we remember the paper as the first one to formalise the term ‘functional response’ although the early citations to this paper are in reference to density dependence, competition, population regulation and population variability e.g. (Elton 1949; Glen 1954; Southwick 1955; Bakker 1963). Interestingly, one of the earlier papers to cite Solomon, (Burnett 1951) presented functional response curves but did not mention the term (Watt (1959)). To add further insult to injury, Holling (1959) in the same year, in his classic paper in which he described and numbered the types of functional responses did not even refer to Solomon, rather deferring to Watt’s paper (loc. cit.). Since then, with the likes of Varley, Gradwell and Hassell (1973) and luminaries such as Bob May (May 1978), this paper has been cited often, and justifiably, and continues to influence us to this day, including the author of this eulogy (Aqueel & Leather 2012). This paper as well as being  the first one to formalise the term ‘functional response’ was the first attempt to draw together the disparate conceptual strands of the first half of the twentieth century work on population dynamics in one coherent whole. Truly, a remarkable and very influential paper.

References

 

Aqueel, M. A., & Leather, S. R. (2012) Nitrogen fertiliser affects the functional response and prey consumption of Harmonia axyridis (Coleoptera: Coccinellidae) feeding on cereal aphids. Annals of Applied Biology, 160, 6-15.

Bakker, K. (1963) Backgrounds of controversies about population theories and their terminologies. Zeitschrift fur Angewandte Entomologie, 53, 187-208.

Burnett, T. (1951) Effects of temperature and host density on the rate of increase of an insect parasite. American Naturalist, 85, 337-352.

Elton, C. (1949) Population interspersion: an essay on animal community patterns. Journal of Ecology, 37, 1-25.

Glen, R. (1954) Factors that affect insect abundance. Journal of Economic Entomology, 47, 398-405.

Holling, C. S. (1959) Some characteristics of simple types of predation and parasitism. Canadian Entomologist, 91,385-398.

May, R. M. (1978) Host-parasitoid systems in patchy environments: A phenomenological model. Journal of Animal Ecology, 47, 833-844.

Solomon, M. E. (1969) Population Dynamics. Edward Arnold, London.

Southwick, C. H. (1955) The population dynamics of confined house mice supplied with unlimited food. Ecology, 36, 212-225.

Varley, G. C., Gradwell, G. R. & Hassell, M.P. (1973) Insect Population Ecology: An Analytical Approach. Blackwell Scientific Publications, Oxford.

Watt, K. E. F. (1959). A mathematical model for the effect of densities of attacked and attacking species on the numbers attacked. Canadian Entomologist, 91, 129-144.

 

Post script

A few months ago I was privileged to be given Robert Tillyard’s excellent The Insects of Australia and New Zealand (first published in 1926), by a former colleague of mine.

Tillyard

What made this even more special was that it had originally belonged to the great Maurice Solomon when he was a student, and contained some of his original annotations and revision notes.

Solomon combo

 

Footnotes

*This is an expanded and updated version of the article I wrote as part of the British Ecological Society’s Centenary celebrations in 2013

**It is probably wishful thinking, but I might be tempted to think that by writing about this influential but somewhat overlooked paper, I increased the number of citations, so had a positive influence 🙂

***The Studies in Biology series, published by the then Institute of Biology (Now Royal Society of Biology), were excellent little books and the series on plant physiology were the main reason that I passed my first year plant physiology module as an undergraduate at Leeds University. I am reliably informed that there are plans to revive the series next year.

 

3 Comments

Filed under Entomological classics, Ten Papers That Shook My World

Serious Fun with Google Trends

No doubt I am behind the curve, but I have only recently discovered Google Trends; a result of attending a Departmental seminar given by a colleague talking about Biochar!

To quote WikipediaGoogle Trends is a public web facility of Google Inc., based on Google Search, that shows how often a particular search-term is entered relative to the total search-volume across various regions of the world, and in various languages. The horizontal axis of the main graph represents time (starting from 2004), and the vertical is how often a term is searched for relative to the total number of searches, globally.”  I was greatly taken by my colleague’s slide showing the birth and development of a new concept

Trends1

and wondered if this would be a useful tool to look at some entomological topics.  Immediately after the seminar I rushed back to my office, and as you may have guessed, entered the word “aphid” into the search bar and was, after a bit of computer chuntering, rewarded with my first Google Trend output  🙂

Trends2

Trends3

I was immediately struck by how closely this resembled real aphid population

Trends4

data, albeit a more regular and smoother than these examples of real  data.  I found that if you ran the cursor along the data lines the month was displayed, and as I expected, the peak in aphid interest was generally June and May, reflecting their peak abundance in the field.   I next entered

Trends5

“Ladybird” to see if it coincided with aphid peaks and interestingly found that it had two peaks within each year, May, when they start to become active and October when they start to look for hibernation sites, so as with aphids, the frequency of the search term usage reflects biological activity.  “Butterfly” and “Ant” as search terms revealed that interest in ants and butterflies has remained

Trends6

fairly constant over the last decade or so, although somewhat to my surprise, ants have had proportionately more searches than butterflies.  Given my worries about the declining interest in plant sciences and the funding problems facing

Trends7

entomology, I thought it might be educational to compare botany and entomology.

Not an encouraging picture, although at least the decline has plateaued out.  Then, just in case, as in many universities, Botany departments have been replaced with Plant Science departments, and is now taught under that title,

Trends8

I substituted “Plant Science” for “Botany” and was surprised to see that “Entomology” was searched for about twice as many times as “Plant Science”.

Comparing “Botany” with “Plant Science” reveals that “Botany” was searched for considerably far more than “Plant Science”, despite most universities no longer having Botany Departments. Perhaps they should reconsider their decision to do away with the title?

Trends9

Keeping with the subject theme and having written in the past about how molecular biology has gained funding and kudos at the expense of whole organism biology (Leather & Quicke, 2010) I compared “Entomology” with

Trends10

“Botany” and “Molecular Biology” to find, that although overall “Molecular Biology” beats both subjects, interest in the subject has also declined over the last decade. One of my bugbears is the amount of interest and funding that the so called “charismatic mega-fauna” gain at the expense of, in my opinion, the much more deserving invertebrates.

Trends11

I therefore compared “Giant Panda”, with “Insect” and “Entomology” and was pleasantly surprised to see that “Insect” wasn’t quite overshadowed by “Giant Panda” although somewhat saddened to see that the whole discipline of “Entomology” was not overly popular.

I confess that felt a little frisson of delight when I found that in recent years “Asian giant hornet” has been giving the “Giant panda” a bit of competition 🙂

 

Trends12

Recently there has been huge debate over the use of neonicotinoids and their possible/probably part they may have in the decline of bees of all sorts (Jeff Ollerton’s blog is a good place to follow the latest news about the debate), so I used “Bee” “Bumblebee” and “Neonicitinoid” as search terms and was

Trends13

surprised to find that “Neonicitinoid” in this context has not really had an impact, although if you search for “Neonicitinoid” by itself you

Trends14

 

can see that there is an increasing interest in the topic.  A corollary to the banning of pesticides or a call for a reduction in their usage as outlined by the EU Sustainable Use Directive, should be an increased interest in the use of alternative pest control methods, such as

Trends15

This does not, however, appear to be the case, with interest in biological control and IPM being at their highest in 2004-2006 and despite the ‘neonictinoid debate’ no signs of interest increasing, which is something to puzzle about.

It appears that there is definitely something to be learnt from using Google Trends, although it would be more useful if some indication of the actual number of searches could be made available.  A word of caution, make sure that your search term is well defined, for

Trends16

example a general search using “butterfly” will give you results for the swimming stroke as well as for the insects.

Although you can compare different geographical regions, and also see the figures for related searches,  what does seem to be lacking,

Trends17

or perhaps I have been unable to find it, is a way to compare different locations at the same time on the same graph.

I would be very interested to hear from any of you who have used this already and also from any of you who are inspired to use this by my post.  Please do feel free to comment.  Have fun!

References

Estay, S.A., Lima, M., Labra, F.A., & Harrington, R. (2012) Increased outbreak frequency associated with changes in the dynamic behavour of populations of two aphid species. Oikos, 121, 614-622.

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

7 Comments

Filed under EntoNotes, Uncategorized

The Dead Entomologists Society

The late and the great: who are the most influential dead entomologists?

In the run-up to the Christmas holidays an ex-student of mine, Andy Salisbury, now at RHS Wisley, and I were discussing who were the most influential dead entomologists ever.  We had begun our discussion discussing Harold Maxwell-LeFroy, http://en.wikipedia.org/wiki/Harold_Maxwell-Lefroy, who among other claims to fame, was the first editor of Annals of Applied Biology http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1744-7348 , the founder of Rentokil and former Professor of Entomology at Imperial College.  He was also famous for having killed himself accidentally whilst trying out a pesticide.

Lefroy conversation

Dead entomologists

Up until the early part of this century he was commemorated in the Biology Department at Imperial College’s Silwood Park Campus with a laboratory named after him; sadly with the move into the new Hamilton Building this no longer exists.

We agreed that the great Alfred Russel Wallace was the most influential entomologist of all time; we felt that claiming Darwin as an entomologist, although famous for his beetle collecting, and despite being a Fellow of the Royal Entomological Society, might be a step too far.  So after Wallace, who was the most influential dead entomologist?

I think that this depends on how you define influential – for entomologists of my generation and the one before us, i.e. those born between 1930 and 1960; Imms and Wigglesworth are probably the two who most influenced us mainly because they were our recommended undergraduate texts  (those were the days when you could do entomology  in the UK as an undergraduate);

Wigglesowrth & Imms compresed

today I guess these have been replaced by Chapman’s The Insects: Structure and Function and Gullan & Cranston’s Outline of Entomology.  But of course outside the field of entomology who remembers Imms and Wigglesworth?  So we should, I think, be looking for entomologists whose influence has extended more widely;  a slightly tongue in cheek contender would be Thomas Moufet,  http://en.wikipedia.org/wiki/Thomas_Muffet who is possibly apocryphally, remembered for the nursery rhyme about his daughter Little Miss Muffett and more substantiated, for his compilation of the Theatre of Insects, but he was mainly a man of

Moufet book

medicine and more interested in spiders than insects in general.  A contender widely known outside the entomological world would be H W Bates, http://en.wikipedia.org/wiki/Henry_Walter_Bates#Taxonomy who is today remembered in the term Batesian

Henry Walter Bates

mimicry  http://en.wikipedia.org/wiki/Mimicry#Batesian ; as a former President of the Royal Entomological Society (1868-1869) I think that we can safely claim him as an entomologist.

Other entomologists that have had an influence  on the rest of the non-entomological world, albeit not widely known outside the biological or medical sciences are Fabre and his Lives of  various insects http://en.wikipedia.org/wiki/Jean-Henri_Fabre , Karl von Frisch http://en.wikipedia.org/wiki/Karl_von_Frisch for his work on honeybees, especially in deciphering the waggle-dance,  E B Ford for his work on ecological genetics and for inspiring Kettlewell’s work on Biston betularia,  http://en.wikipedia.org/wiki/E._B._Ford  and more recently Richard Southwood  http://en.wikipedia.org/wiki/Richard_Southwood   (Methods in Ecology) but initially a Hemipteran specialist and Miriam Rothschild  http://en.wikipedia.org/wiki/Miriam_Rothschild for her work on a range of entomological subjects but very famously for her work on fleas.

The acid test of course, is how many living entomologists the man or woman in the pub can bring to mind when asked, let alone those that have joined the Dead Entomologist’s Society. Perhaps it is the fate of entomologists to be largely overlooked, much like the small but highly important organisms we work on 😉

I would dearly love to hear your thoughts on which the most influential dead entomologists are.  I am well aware, that my list is very Euro- and UK-centric.  So let’s see some nominations from the rest of the world, suitably justified of course!

Post script

Getting my vote as a contender for an American entomologist of great influence, albeit British-born, would be Charles Riley, sometimes known as the Father of Biological Control http://en.wikipedia.org/wiki/Charles_Valentine_Riley , but then again, who outside the world of entomology has heard of him?

14 Comments

Filed under EntoNotes

Pest Managers are ecologists too

Over the course of the last decade I have come to the conclusion that British undergraduates have no idea of what pest management actually is.  For the last twenty years or so, I have run a suite of MSc courses, initially at the Silwood Park campus of Imperial College and since 2012, at Harper Adams University, the leading land-based university in the UK.  The four MSc courses I run are Conservation and Forest Protection, Ecological Applications, Entomology and Integrated Pest and Disease Management.  These are, as you can see, pretty much specialist vocational courses.  The students who do these courses are highly motivated and come from a range of backgrounds.  Many had established careers in other areas and found those careers lacking.  Others have had a burning desire to embark on advanced training in entomology since they were at school and been deeply frustrated that no undergraduate degrees exist in the UK in that subject. [The last BSc in Entomology in the UK was awarded in 1993 by Imperial College to Andy Salisbury (now Dr Andrew Salisbury and Senior Entomologist at the Royal Horticulture Society’s research offices at Wisley].  Yet others have developed an interest in one of the areas covered by my MSc courses as undergraduates and decided to make a career in those areas, but found that their BSc degrees had not prepared them to the required level in their chosen subject and that they needed the extra training provided by a postgraduate course.  The interesting thing to me is how the absolute interest in integrated pest management has remained at pretty much the same level year on year, at just under 5 with a high of 9 students in 1989 and in 1998 no students at all.  Over the same period the average number of entomologists on the course was twelve. As a proportion of the student body the pest management contingent has ranged from a very disappointing zero to the memorable year, 2004, when there were twice as many pest managers as entomologists, albeit out of total student body of only nine.

MSc Entomology and IPM students

MSc Entomology and IPM students

Pest managers are in great demand from industry –biological control and agrochemical companies have more positions than there are suitably qualified graduates; yet undergraduates seem reluctant to train in this area.  I think that there are two root causes for this problem; a lack of exposure to the subject as undergraduates and a misunderstanding of exactly what pest managers are and what they actually do.  Mention pest management to most people, not just students, and their first reaction is rats, cockroaches and Rentokil operatives spraying.

Cockroaches

Cockroaches

The mythical spray man

The mythical spray man

A pest!

A pest!

Yes pest control does involve poisoning vermin and spray operations against domestic insect pests, but that is only one very minor, albeit important, aspect of pest management.  Pest management, or as it is more formally known, Integrated Pest Management, is the intelligent selection and use of pest control measures to ensure  favourable economic, ecological  and sociological consequences.  Yes this does include the use of pesticides but only as part of an integrated programme that could include biological control, the use of resistant plant varieties, and the diversification of the farm landscape through conservation headlands, and cultural methods such as crop rotation or inter-cropping.   Even scare-crows, traditional or modern, can be part of an IPM programme. The list goes on and all this is backed up by a detailed knowledge and understanding of the biology and ecology of the pest species, their natural enemies and the habitats that they live in.

Conservation headland

Conservation headland

Traditional scarecrow

Traditional scarecrow

Intercropping

Intercropping

Biological control

Biological control

The idea of pest management is not an entirely modern one ; Benjamin Walsh a British born pioneer applied entomologist  working in the USA, said in 1866, and I quote,  “Let a man profess to have discovered some new patent powder pimperlimplimp, a single pinch of which being thrown into each corner of a field will kill every bug throughout its whole extent, and people will listen to him with attention and respect.  But tell them of any simple common-sense plan, based upon correct scientific principles, to check and keep within reasonable bounds the insect foes of the farmer, and they will laugh you to scorn”.  I consider this to be the first modern reference to integrated pest management.

               

Pest managers do not just work in domestic and urban situations.  Most pest managers, as opposed to pest control operatives work in agriculture, forestry and horticulture, safeguarding our crops and ensuring global food security.  Pest managers, because of the complexity of the problems facing sustainable crop production in the modern world, have to have a much greater depth and breadth of knowledge than pure ecologists.   Although many pest managers have entomological backgrounds, they also have a more than nodding acquaintance with plant pathology, nematology and pesticide application and chemistry.  They also need to have a good grasp of the economics of both pest control and the farming/cropping system that they are working in.  They must fully appreciate what is feasible and appropriate in the context of the farmer’s/forester’s year, budgets and targets in terms of yields and profits.  There is no point in coming up with the ideal ecological or conservation solution that cannot be implemented because of the constraints of the real world.  Pest managers, even those working in academia, interact closely with their end-users, to ensure a reduction in pest numbers and abundance, not necessarily eradication, which is acceptable to growers, society and the natural world.   As Lorna Cole said on Twitter on September 8th 2013….

Lorna Cole

So when you hear the word pest management in future, don’t just think spray, think conservation headlands, beetle banks, biological control, crop rotation, resistant varieties, chemical ecology, forecasting, monitoring , cultural control, holistic farming, multi-purpose forestry, sociology, economics and sustainability.  These are the elements of the armoury most commonly used by pest managers, not pesticides as so many people mistakenly think.

So for prospective students, don’t be put off by the word pest, if you want an exciting, satisfying and possibly international career, embrace the application of ecology and make a difference to the world.   Become a pest manager.  Without integrated pest managers food production will never be sustainable or as ecologically friendly as it now is.

Post Script

Sadly, even to this day (it was much worse when I started my career), there is a perception among some academics that being applied is second best; on one memorable occasion I was introduced to some visitors by one of my colleagues as, “this is Simon Leather, he’s an ecologist, ALBEIT, an applied one”

 

Post post script

 

For those interested in joining the MSc course in Integrated Pest Management based at Harper Adams University here is the appropriate link.  I should also add that unfortunately we are NOT able to offer three annual Scholarships funded by the Horticultural Development Council, HDC, of £5000 each to particularly deserving students as despite ALL our graduates finding employment in the industry they felt that the scheme was not working!

10 Comments

Filed under Bugbears, EntoNotes

Desperately seeking sources: the quest for the original citation

From 1993 until 2012 I taught a final year course at Imperial College called Applied Ecology.  The relevant part of the course blurb used to say:

Course Outline:  Applied ecology, philosophy and concepts.   Nature Conservation, Nature Reserves (history and philosophy), SSSIs, legal aspects, SLOSS, butterfly case studies.  Mammal conservation, issues and dilemmas.   Forestry and woodland management, effects of afforestation, effects on pest and disease incidence, conservation. Habitat creation and management.  Waterways and fisheries. Agroecosystems, agricultural practice and objectives, crop history and evolution, pest incidence. Organic farming, effects on pest incidence, weeds, workshops.  Pest management and the environment, residues, niche replacement, biocontrol, resistance, social and economic effects, IPM in harmony with conservationists. Sampling, forecasting and monitoring. Workshops and mini-conference. Visit to London Zoo (Captive breeding programme).

Those of you with eagle eye vision may have noticed that one of the topics covered was biocontrol; for those of you with vision more like mine, I have highlighted the word biocontrol in bold. As most of this course was material that I had lived and breathed either since I was an undergraduate, or as part of my professional research career (except for the rivers and lakes), I was in the enviable position of not having to do a lot of background research to prepare lectures and source material.  It was quite literally, sitting there in my head.  This did of course lead to some sloppy habits.  For example, as an undergraduate my crop protection lecturer at Leeds (the late Dr Noel Gibson) when telling us about biological control and its history, mentioned that the Chinese had, long ago, introduced ant nests to citrus orchards and to enhance their activities, stretched bamboo poles between trees.  So to my lazy self, this was a fact and thus when preparing my slide on the history of biological control I put it down as a fact without acknowledging any source [something I happily tell students and others off for not doing!].

bological control slide

I sort of felt guilty about this but always said in the lecture that this is what my lecturer had told me when I was an undergraduate and as none of the students ever asked me for the actual reference I let it slide.  Then one year (2006), I was reading a science fiction novel by a Scottish novelist, Kenneth McLeod, who just so happens to have a degree in zoology.  The book, as far as I remember, described the attempts of earth colonists attempting to establish crops on an alien planet.  Their crops were being devastated by pests and the xeno-biologist said, and I quote very loosely, as this was back in 2006, said (and I am sure you have guessed it already) “I remember my lecturer telling me when I was an undergraduate about how the Chinese used to facilitate biological control by running bamboo poles between orange trees so that the ants could be more effective”.  “Wow”  I said, and “Wow” again, because Ken McLeod had put a reference in a footnote, to Wheeler (1910).  So there was my source.  I now had a mission. Despite the fact that I had accepted the story as fact since 1976, I felt an urgent need to see the reference for myself.  Using the internet I tracked down a copy of Wheeler in an antiquarian book shop in Amsterdam and ignoring the sarcastic comments of my wife, purchased it on-line and waited impatiently for it to arrive.  As we were now in the Christmas vacation it didn’t arrive until the New Year.  I ripped open the parcel and was the proud owner of a copy of Wheeler’s Ants ; interestingly, the copy I now owned had once been in the library stock of Cornell University, so had made rather a long journey to end up in Bracknell almost a hundred years later.

Wheeler

I started to read it; luckily I didn’t have to go very far as there on page 9 was the story of the Chinese ants in black and white; unfortunately, it appeared that Wheeler was not the primary source, he was indulging in yet another bug-bear of mine, quoting someone,

Wheeler page 9

McCook (1882), who had quoted someone else (Magowan), without giving the original source.  So now I had to track down McCook!

McCook refs

Luckily, since Wheeler had actually cited McCook, I was able to do this successfully using the inter-library loan service.

McCook 1882

So now I had the citation for Magowan.  Unluckily it was in rather an obscure newspaper, The North China Herald.  This posed a bit of a problem and slowed my search down.  Luckily in recent years, there has been a huge international effort made into digitising newspapers and I was finally able to track down an electronic archive holding the relevant issue and

North China Herald front page

eventually find the relevant page.  Success, after almost seven years I had finally tracked down the original source of the ‘fact’ that I had been retelling for all those years. I felt quite

North China Herald page zoom 363

proud of myself , although my wife, who is not a scientist, says that this is yet another example of how weird we scientists are.  On the other hand, I was somewhat disappointed that I had only tracked it down to 1882 as I am sure that this must be an ancient agricultural practice with its roots, many hundreds, if not thousands of years in the past.  Perhaps my next self-imposed mission impossible, will be to find the oldest mention of the practice.

 Post script

Today, I just happened to be looking for a book in my office, when I noticed one of my old course texts, Van den Bosch & Messenger (1973),

Van Den Bosch    Inside van den Bosch

which I notice cost me £2 in 1976, actually quite a lot of money as my student grant was just over £600 in total.

Flicking the book open I soon found the page with the Chinese ant story on it and a citation to the 1882 McCook paper.  So, if I had thought to look at my old text-book I could have saved myself the expense of buying Wheeler’s book, which was not cheap.  But then if I had, I would never have discovered Wheeler and I would have missed all the fun of chasing the references down, so I think it was worth it overall.

References

McCook, H.C. (1882) Ants as beneficial insecticides. Proceedings of the Academy of Natural Sciences Philadelphia, 34, 263-271.

 van den Bosch, R. & Messenger, P.S. (1973) Biological Control, Intertext Books, New York & Leighton Buzzard.

Wheeler, W.M. (1910) Ants: Their Structure, Development and Behavior, Columbia University Press, New York & London.

2 Comments

Filed under Bugbears, EntoNotes, Teaching matters