Tag Archives: ladybirds

Ten papers that shook my world – Lewis (1969) – the importance of (h)edges for natural biological control

In 1969, Trevor Lewis, of what was then the Rothamsted Research Station (now Rothamsted Research), published two landmark papers (Lewis 1969ab). These papers, in which he described the importance of hedges as habitats for insects (Lewis, 1969a) and in acting as possible sources of natural enemies able to colonise nearby fields (Lewis, 1969b) were to have a profound effect on me and generations of applied entomologists and pest mangers to the present day.

In 1976 the UK experienced what is now recognised as the warmest year of the 20th Century.  It was also the year that I started my final year as an undergraduate.  Before entering our final year we had to do a research placement or project.   I opted to do my project at home, I was making very good money as a temporary postman and as I usually finished my round by 10 am, I had plenty of time during the rest of the day to get to grips with my project.  I had come across the Lewis papers in lectures and thought that it would be interesting to do a similar study; given the weather I was also keen to spend as much time outside as possible 🙂 My Uncle James owned a local farm and was happy for me to sample some of his hawthorn hedges, so sampling hawthorn hedges was what I did during July and August of the glorious summer.

Simon summer 1976

The intrepid student entomologist; trusty bike, clipboard and a copy of Chinery*. Note the wellington boots despite the heat 🙂

The hedges

The hedges in question – three types of management

As I mentioned earlier, 1976 was the warmest year on record at the time, and I see from my report that during August I was recording temperatures in excess of 25oC, even in the hedge bottoms.

Hedges project

The report

What is interesting is that although 1976 was one of the famous ladybird outbreak years (in fact last week I was interviewed by the BBC about my memories of that very same event) I didn’t record more than a handful of ladybirds in my surveys.  Perhaps inland Yorkshire just wasn’t attractive enough 🙂

Overall my results showed that over-clipping resulted in more crop pests being present and that hedges with less clipping supported a greater diversity of insect life than the more managed ones, very similar to results being reported today (e.g Amy et al., 2015).

Sadly, although Lewis’s two 1969 papers and to a certain extent his earlier paper in a much harder to access source (Lewis, 1964), led on to the concept of conservation headlands (Sotherton et al., 1989) and ‘crop islands’ (Thomas et al., 1991), which are an integral part of European Union subsidised farm payments, it was included in an influential review article (van Emden & Williams, 1974).  As pointed out recently by Terry McGlynn over at Small Pond Science, this often rings the death knell for a paper’s citation score.  As a result,  Lewis (1969b) has only been cited 91 times since 1969 and is barely remembered at all.   I remember being invited to be a facilitator at a Populations Under Pressure conference workshop on this very subject at the NERC Centre for Population Biology at Silwood Park about fifteen years ago and being surprised that none of the participants had even heard of Trevor Lewis let alone read his papers.

Simon PUP

At the Populations Under Pressure conference brandishing my undergraduate hedgerow report!

The subject of hedgerow and crop edge management is still a highly important research area today, and you will be pleased to know that in the latest paper just submitted from my research group, we cite both of Trevor’s 1969 papers. Hopefully this will do something to redress the balance and bring Trevor some of the recognition that he deserves, however belated.

 

References

Amy, S.R., Heard, M.S., Hartley, S.E., George, C.T., Pywell, R.F. & Staley, J.T. (2015) Hedgerow rejuvenation management affects invertebrate communities through changes to habitat structure. Basic & Applied Ecology, 16: 443-451

Chinery, M. (1973) A Field Guide to the Insects of Britain and Northern Europe.  Collins, London

Lewis, T. (1964). The effects of shelter on the distribution of insect pests. Scientific Horticulture, 17: 74–84

Lewis, T. (1969a). The distribution of flying insects near a low hedgerow. Journal of Applied Ecology 6: 443-452.

Lewis, T. (1969b). The diversity of the insect fauna in a hedgerow and neighbouring fields. Journal of Applied Ecology 6: 453-458.

Sotherton, N.W., Boatman, N.D. & Rands, M.R.W. (1989) The “Conservation Headland” experiment in cereal ecosystems. The Entomologist, 108: 135-143

Thomas, M.B., Wratten, S.D., & Sotherton, N.W. (1991) Creation of ‘island’ habitats in farmland to manipulate populations of beneficial arthropods: predator densities and emigration. Journal of Applied Ecology, 28: 906-917.

Van Emden, H.F. & Williams, G.F. (1974) Insect stability and diversity in agro-ecosystems. Annual Review of Entomology, 19: 455-475

*I still own that copy of Chinery which was a present for my 20th birthday – take note of the date if anyone wants to send me a present or card 🙂

 

Chinery

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Filed under Ten Papers That Shook My World

Not all aphids taste the same

One morning sometime in the late 1970s, when I was doing my PhD at the University of East Anglia, I walked into the lab to find one of my fellow PhD students sitting in front of a row of Petri dishes filled with different species of aphids.  Curious, I asked him what he was doing.  His reply was that he was tasting the aphids to see why his ladybirds made the choices they did.  This was a guy whose hobby was collecting and identifying Chamaemymiid flies, so I was not entirely surprised, although I did point out that it was unlikely his taste receptors and those of the two-spot ladybird (Adalia bipunctata) had a lot in common.

Aphid tasting cartoon

That said, his premise that aphids don’t all taste the same was of course perfectly correct.  Aphid predators, in particular ladybirds, seem to have quite strong preferences for different aphid species and these preferences are strongly correlated with larval development and subsequent fecundity as adults (Kalushkov, 1998; Kalushkov & Hodek, 2004).  What is perhaps not as well-known is that certain aphids, like many lepidopteran larvae, are extremely good at sequestering potentially toxic chemicals from their host plants.  Over a century ago, Johnson (1907) noted that highly coloured and woolly (in this case meaning waxy) aphids were not eaten as readily as smoother, greener aphids.  Half a century later Hodek (1956, 1957), showed that larvae of the seven spot ladybird (Coccinella septempunctata) were unable to complete their development if fed a diet of the elder aphid Aphis sambuci and that young adult ladybirds died if fed on the same diet.  Note that A. sambuci although not brightly coloured has waxy plaques on its abdomen.

Aphis sambuci

Aphis sambuci  http://aramel.free.fr/INSECTES10-4′.shtml

The mealy plum aphid, Hyalopterus pruni, although bright green, is also waxy, and when attacked by larvae of the ten spot ladybird, Adalia decempunctata, is released as oon as the ladybird larva comes into contact with the aphid’s haemolymph (insect blood) (Dixon, 1958).

Hyalopterus pruni

Hyalopterus pruni, the mealy plum aphid http://influentialpoints.com/Gallery/Hyalopterus_pruni_Mealy_Plum_Aphid.htm

The vetch aphid Megoura viciae, on the other hand, is rather a handsome dark green aphid, with startlingly red eyes.  If however, a larva of the ten-spot ladybird is foolish enough to eat

Megoura viciae

Megoura viciae, the vetch aphid  http://influentialpoints.com/Gallery/Megoura_aphids.htm

one, it will, after about two minutes, be violently sick.  Those are the lucky ones; those that don’t regurgitate the aphid are very likely to die a few days later.  The two spot aphid, Adalia bipuncatata is also killed if it is unlucky enough to eat M. viciae (Blackman, 1967).  It appears that the vetch aphid is full of all sorts of interesting and potentially fatal chemicals (Dixon et al., 1965). Truly a toxic treat.  Megoura viciae is not the only toxic aphid out there.  Aphis craccivora, the cowpea aphid, is a beautiful mahogany brown aphid, but despite its attractive

Aphis craccivora

Aphis craccivora, the cowpea aphid

appearance, it is extremely toxic to the eleven spot ladybird Semiadalia undecimnotata, although the seven spot ladybird finds it perfectly acceptable (Hodek, 1970).

A similar effect is seen with the cabbage aphid, Brevicoryne brassicae, which is extremely good at sequestering glucosinolates, especially sinigrin, from its Brassica host plants.  Glucosinolates are the compounds that give cabbages and related plants, such as Brussels sprouts, their distinctive flavour.  In high dosages they can cause liver damage in young mammals, one of the reasons why children are so reluctant to eat cabbage, despite their parent’s urgings.  Brevicoryne brassicae is so good at sequestering  glucosinolates that larvae of the two spot ladybird die when fed on aphids from sinigrin rich cabbages (Kazana et al., 2007). The seven spot ladybird however, although not entirely happy when fed on a diet of sinigrin- rich cabbage aphids is able to survive, develop and reproduce successfully (Pratt et al., 2008).  It obviously has a much better detoxification system than that of the two spot ladybird which for an aphidophagous predator seems singularly specialist.

Seven spot ladybird (Corin Pratt)

Brevicoryne brassicae – the cabbage aphid; a colony being approached by a hungry seven spot ladybird (Photo Corin Pratt & Tom Pope).

Another aphid that sequesters plant derived toxins is the Stinkvine aphid, Acyrthosiphon nipponicus, which accumulates an iridoid glycoside, paederoside from it’s host plant the stinkvine Paederia foetidae (syn = scandens) (Nishida & Fukami, 1989). This brightly coloured aphid does not have to merge into the background; its chemical defence is so strong that

Acyrthosiphon nipponicus

Acythrosiphon nipponicus – Stinkvine or Skunk-vine aphid http://homepage3.nifty.com/MICHI_A/akigase/AKIGASEKOUEN_hannsimoku2-1.htm

even that voracious predator the Harlequin ladybird, Harmonia axyridis, turns tail when dabbed with the aphid’s siphuncular fluid, or if it is unlucky enough to bite into the aphid, drops the aphid, regurgitates and rapidly leaves the leaf on which the aphid colony is feeding.

And finally, this striking, although rather noxious yellow aphid, the oleander aphid, Aphis nerii, which very honestly advertises that it is indeed a mouthful to be avoided.

Aphis nerii

Aphis neri – the oleander aphid http://www.zenthroughalens.com/2012/01/aphis-nerii-and-i.html

Aphis nerii is packed full ofcardiac glycosides which it sequesters from its host plant(Rothschild et al., 1970) and provides a powerful defence against potential predators, not just ladybirds.

So bear in mind, that although aphids may seem to be soft-bodied, small and defenceless, many of them are extremely well defended chemically as well as behaviourally.  This suite of complex defence mechanisms may go some way to  explain the ability of aphids to keep at least one step ahead of their natural enemies.

References

Blackman, R.L. (1967) The effects of different aphid foods on Adalia bipunctata L. and Coccinella septempunctataAnnals of Applied Biology, 59: 207-219  http://onlinelibrary.wiley.com/doi/10.1111/j.1744-7348.1967.tb04429.x/abstract

Dixon, A.F.G. (1958) The escape responses shown by certain aphid to the presence of the coccinellid Adalia decmpunctata.  Transactions of the Royal Entomological Society London, 110: 319-334  http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2311.1958.tb00786.x/abstract

Dixon, A.F.G., Martin-Smith, M. & Subramanian, G. (1965) Constituents of Megoura viciae Buckton. Journal of the Chemical Society, 296: 1562-1564.

Hodek, I. (1956) The influence of Aphis sambuci L. as prey of the ladybird beetle Coccinella septempunctata L. Acta Societatis Zoologicae Bohemoslovacae, 20: 62-74 (in Czech)

Hodek, I. (1957) The influence of Aphis sambuci L. as prey of the ladybird beetle Coccinella septempunctata L. II. Acta Societatis Entomoligicae Cechosloveniae, 54: 10-17 (in Czech)

Hodek, I. (1970)  Coccinellids and the modern pest management. BioScience, 20:543-552

Johnson, R.H. (1907) Economic notes on aphids and coccinellids.  Southwestern Entomologist: 12: 107-118

Kalushkov, P. (1998). Ten aphid species (Sternorrhyncha: Aphididae) as prey for Adalia bipunctata (Coleoptera: Coccinellidae). European Journal of Entomology 95: 343-349. http://www.eje.cz/scripts/viewabstract.php?abstract=412

Kalushkov, P. &Hodek, I. (2004). The effects of thirteen species of aphids on some life history parameters of the ladybird Coccinella septempunctata. Biocontrol 49: 21-32. http://link.springer.com/article/10.1023%2FB%3ABICO.0000009385.90333.b4

Kazana, E., Pope, T.W., Tibbles, L., Bridges, M., Picket, J.A., Bones, A.M. & Rossiter, J.T. (2007) The cabbage aphid: a walking mustard oil bomb. Proceedings of the Royal Society B., 274: 2271-2277. http://rspb.royalsocietypublishing.org/content/274/1623/2271.full

Nishida, R. & Fukami, H. (1989) Host plant iridoid-based chemical defense of an aphid, Acyrthosiphon nipponicus, against ladybird beetles.  Journal of Chemical Ecology, 15: 1837-1845  http://link.springer.com/article/10.1007/BF01012270

Pratt, C., Pope, T.W., Powell, G. & Rossiter, J.T. (2008)  Accumulation of glucosinolates by the cabbage aphid Brevicoryne brassciae as a defence against two Coccinellid species.  Journal of Chemical Ecology, 34: 323-329 http://link.springer.com/article/10.1007/s10886-007-9421-z

Rothschild, M., von Euw, J. & Reichstein, T. (1970)  Cardiac glycosides in the oleander aphid, Aphis neriiJournal of Insect Physiology, 16: 1141-1145

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Filed under Aphidology, Aphids