Tag Archives: winter

The Natural World in Haiku form

Traditionally in the world of journalism, August is regarded as lacking any news of note, and is, in the UK at any rate, dubbed the “Silly Season”.  In homage to that view-point, and instead of doing one of of my usual blog posts, I searched for all the haikus I have tweeted over the last three years and present them here for light relief.

 

Thirsty snails

Short of water, snails

Circle and swirl on the rocks,

Waiting for a storm.

All the stones of any consequence were encrusted with snails.  Then the rain came and they were gone.

Italy 25 July 2014

 

Evening lift-off

Italian evening;

Bats swoop as stag beetles lift

Into lurching flight

Note the hole in the left elytrum, the resident kitten at our Italian holiday villa really enjoyed herslf snatching the poor lumbering beasties (in this case a Rhinoceros beetle) out of the air ☹

Italy 27 July 2014

 

Breakfast?

Italian morning;

Lizards scurry on the stairs

as cicadas sing

Admittedly not on the stairs, but close enough 😊

28 July 2014

 

Seasons

 

Spring has sprung

 White, pink fluttering,

the gentle breeze scattering;

cherry blossom falls

Outside my office – 24 May 2016

 

Summer?

Blue sky, sun shining

Ducklings following mother

Winged aphids – summer?

4 May 2016

 

Summer?

Dull, damp, cold drizzle.

Clouds glowering down on me.

Flaming June my foot 😦

29 June 2017

 

St Martin

September sunshine;

Eating lunch sitting outside.

What could be better?

10 September 2014

 

On the way

 September morning,

Sunlit, moist mist-laden trees;

Autumn is coming

8 September 2014

Autumn

Crickle, crackle; leaves,

underneath my slipping feet.

Autumn is with us.

20 October 2015

 

I used to camp here as a lad!

Sodden tent, wet feet.

Rolling hills and drystone walls.

English Lake District

8 October 2014

 

Damp

How I hate mizzle;

as wet as real rain, but no

comforting refrain

26 November 2015

 

Satisfaction

Shuffling through brown leaves

On a sunny autumn day;

So satisfying.

2 November 2016

 

Wet Pavements in Lille

Desert boots are great

except when soles are holey.

Then rain means wet feet

10 December 2014

 

Transience

Icing sugar snow,

Gently being washed away;

Grey drizzle falling

29 January 2015

Miscellanea

 

Job downside

Academics hate

marking student assignments

on a sunny day

7 December 2016

 

Sunday lunch

 Butterflied mint lamb

roast potatoes and carrots;

apple and pear tart.

11 December 2016

 

Dedicated to @IMcMillan who spends a lot of time at stations

Cardboard coffee cups

tentatively raised to lips;

Morning commuters

7 July 2016

 

Definition

Searching for the why

and how things are like they are;

Entomology

20 December 2015

 

Blood Moon

Lustrous, silver orb

Bloody, awe-inspiring moon

Night-time amazement

28 September 2015

 

Evening entertainment

Bats, swiftly looping

Snatching insects from the sky

Feeding on the wing

26 July 2017

 

Regular readers, rest assured, normal service will be returned in the next post 🙂

Leave a comment

Filed under The Bloggy Blog, Uncategorized

A Christmas Aphid

A few weeks ago I was contacted by a researcher from the One Show.  They were interested in the possibility of doing a festive piece about what people bring into the house with them on Christmas trees with the idea that George McGavin would shake a Christmas tree over a piece of white paper and tell the audience all about the insects that fell out;  a typical media “how gross nature” is piece.

The researcher was somewhat disappointed when I told her that being winter  that there would be relatively little hiding in the tree, especially if it was a commercially reared cut tree bought from a garden centre or other retail outlet.  Cut Christmas trees in the UK tend to be harvested from October onwards so the chances are that your tree has lain about for at least a month before you bring it into your house and by that time, any sensible winter active herbivore has long departed for fresher trees.  Although conifer trees have a large number of insect species associated with them, most of them spend the winter either off the tree or as inactive eggs hidden under the bark or as eggs actually laid inside the needles e.g. the pine sawfly Neodiprion sertifer.  You would probably find a few opportunistic spiders and possibly some mites and bark lice, but not much else unless you had a potted tree or one that had only recently been felled.  The other thing that would influence what you would find is of course what species of tree you had bought.  Gone are the days when the Christmas tree and Norway spruce (Picea abies) were one and the same.  I guess my caveating and pessimistic reply proved too much for the researcher as I never heard back from her.

The one insect I had waxed lyrical about was of course an aphid, the green spruce aphid, Elatobium abietinum to be precise.   There are a number of aphid species that make a living on spruce trees, some of them quite large and spectacular such as the greater black spruce aphid, Cinara piceae, but like most aphids, they overwinter as eggs (Leather, 1992).

Cinara_piceae_aptera_on_Picea_abies_at_Selwyn_Wood

The greater black spruce aphid, Cinara piceae (Photograph courtesy of http://influentialpoints.com/Gallery/Aphids_on_spruce_Picea_in_Britain.htm)

The green spruce aphid, E. abietinum or Elatobium as it is commonly known, (there is only one species in the genus), overwinters in the UK and most other parts of the world, as an adult or immature stage (nymph) (Nicol et al., 1998).

The adult is small, green and inconspicuous, and quite difficult to see unless you are actually looking for them.

Elatobium and nymphs

The green spruce aphid, Elatobium abietinum and nymphs.

The green spruce aphid is a native of Europe and normally attacks Norway spruce.  They avoid current year needles as these tend to be distasteful to them (the chemistry of young spruce needles is pretty nasty and makes them unsuitable hosts for the aphids) and feed on the previous year and older needles.  Spruce needles, even older ones, are not particularly nutritious, so the aphid injects a toxic material in its saliva that makes the needles more nutritious by encouraging nitrogen mobilisation (Kloft & Erhardt, 1959).  Their populations build up during the spring and towards the end of May and beginning of June, they take flight and the trees seem relatively free of aphids (Bevan, 1966).  As they are so small, they are most obvious after they have gone, either by the damage they cause, premature senescence of the needles as shown in the photograph above, premature needle drop or by the presence of a large number of ladybird larvae.  When I worked for the Forestry Commission as an entomologist, I quite often received phone calls from distressed foresters who had sprayed the blue beetles damaging their spruce trees!

Although they are difficult to find during the summer months they are still there; this summer collapse of singe-host aphids is quite common (Karley et al., 2004).  In the autumn,  Elatobium populations begin to build up and as they do not overwinter as eggs, they are able to continue reproducing through the winter months (Powell & Parry, 1976). Sitka spruce, Picea sitchensis, the most commonly grown conifer in the UK, is a native of North America and as such has very low resistance to Elatobium and displays an almost hypersensitive response to the toxic saliva produced by the aphid.

If it is a particularly mild winter then the spruce trees are likely to show severe signs of damage by June and July.  After several mild winters spruce trees may end up with only current year needles present, which has a severe effect on their growth and appearance.

Elatobium damage needles

Branches of Sitka spruce with only current year needles present after a severe Elatobium abietinum infestation

Elatobium damage trees

Sitka spruce trees showing discoloured needles after attack by Elatobium abietinum.

It may be small, inconspicuous and not worth a TV appearance, but  Elatobium abietinum is now a pest with a world-wide distribution and an international reputation.

References

Bevan, D. (1966). The green spruce aphis Elatobium (Neomyzaphis) abietinum Walker. Scottish Forestry 20, 193-201.

Karley, A. J., Parker, W. E., Pitchford, J. W. &Douglas, A. E. (2004). The mid-season crash in aphid populations: why and how does it occur? Ecological  Entomology 29, 383-388.

Kloft, W. & Ehrhardt, P. (1959). Unterschungen uber Saugtatigkeit und Schadwirkung der Sitkafichtenlaus, Liosomuphis abietina (Walk.), (Neomyzaphis abietina Walk.).  Phytopathologie Zeitzschrqt 35, 401 – 410.

Leather, S. R. (1992). Aspects of aphid overwintering (Homoptera: Aphidinea: Aphididae). Entomologia Generalis 17, 101-113.

Nicol, D., Armstrong, K. F., Wratten, S. D., Walsh, P. J., Straw, N., Cameron, C. M., Lahmann, C. & Frampton, C. M. (1998). Genetic diversity of an introduced pest, the green spruce aphid Elatobium abietinum (Hemiptera: Aphididae) in New Zealand and the United Kingdom. Bulletin of Entomological Research 88, 537-543.

Powell, W. & Parry, W. H. (1976). Effects of temperature on overwintering populations of the green spruce aphid, Elatobium abietinum.  Annals of Applied Biology 82, 209-219.

Sullivan, C.R. (1965) Laboratory and field investigations on the ability of eggs of the European Pine Sawfly, Neodiprion sertifer (Geoffroy) to withstand low winter temperatures.  Canadian Entomologist, 97, 978-993

 

Postscript

During the 1980s when ‘Acid Rain’ was very much in the news, Elatobium damage was often mistaken as a symptom of acid rain in the UK.

 

3 Comments

Filed under Aphidology, Aphids

A Winter’s Tale – aphid overwintering

Aphids that live in temperate or boreal regions have to be able to survive overwinter. Aphids, depending on species, are able to pass winter in two ways. If they are holocyclic i.e. possess an egg-laying stage, they usually overwinter as eggs. Aphid eggs are extremely cold-hardy; they have been reported to have super-cooling points of about -42oC (Somme ). If laid on a woody host, eggs are usually laid in the bud axils as in the case of the apple aphid, Aphis pomi, the black bean aphid Aphis fabae and the bird cherry aphid, Rhopaloishum padi.

aphid eggs

In some instances, such as the sycamore aphid, Drepanosiphum platanoidis, eggs are laid directly on the tree bark or in crevices in the bark or even in lichen growing on the bark.  See if you can spot the eggs in the picture below.

ovipsyc

If however, the aphid in question lives on an herbaceous host, the eggs may be laid directly on the ground, on or amongst fallen leaves or at the base of grass tussock.

The other strategy adopted by those aphids that are anholocyclic, such as the green spruce aphid, Elatobium abietinum, is to pass the winter as an active stage, either as an adult or immature nymph. Those holocyclic aphids that have anholcyclic strains are also able to adopt this strategy. Despite their soft bodies and fragile appearance, aphids have quite low super-cooling points values such as -26oC having been reported (Griffiths & Wratten, 1979).

A potential advantage of using an active overwintering stage and not an egg, is that if they survive the winter, they are able to start reproducing sooner, particularly if they are a host –alternating aphid, where the aphids hatching from eggs, have to spend time developing and reproducing on the primary woody host before being able to migrate to the secondary hosts. This also applies, to a lesser extent, to those holoyclic aphids living on herbaceous plants, although the temporal advantage is not as great. One would assume that given the relative cold-hardiness attributes of aphid eggs and adults that in a country such as the UK where winter temperatures below -10oC are both infrequent and short lasting, winter survival of aphids would be extremely high if not guaranteed. This is not the case. For example, eggs mortality of the bird cherry aphids is typically around 70-80% as shown in my first ever publication (no fancy graphics packages in those days, just Letraset , Indian ink, stencils and tracing paper). Actually people had measured aphid egg mortality much earlier than this (Gillette, 1908) but I was the first person to monitor mortality throughout the winter and show that it occurred at a steady rate irrespective of the severity of the winter.

 Egg survival

It is actually a function of the length of the winter that determines how many eggs survive, the longer the winter the greater the mortality.

Egg mortality

This level of mortality is typical for all aphid species for which I have data (Leather, 1993). Some of this mortality can be attributed to predation, but most of it is intrinsic (Leather, 1981), possibly due to cryo-injury.

Similarly, those aphids that overwinter as adults or nymphs, despite their ability to super-cool to temperatures below -20oC, experience even greater levels of mortality as shown elegantly by Jon Knight and Jeff Bale in 1986 studying overwinter survival of the grain aphid Sitobion avenae near Leeds.

Knight & Bale

In fact one wonders how any aphids at all survive winter this way, but they certainly do if the winters are mild enough, as in the case of Myzus persicae and Sitobion avenae in southern England and E. abietinum throughout most of its range (Day et al., 2010). An interesting anomaly is Iceland where hot springs abound and the bird cherry aphid is able to survive anholocyclically on grasses growing around the springs whereas in other countries with similar winter temperatures it would only be able to survive as the egg stage.

Despite the importance of winter to aphid population dynamics we still know very little about their winter ecology, our knowledge being confined to a handful of economically important species. Despite the discomfort of field work in the winter this is an area which would be very rewarding to anyone in need of an interesting and good research project.  Finger-less mittens are, however, definitely recommended 😉

Useful references

Bale, J. S. (1996). Insect cold hardiness: a matter of life and death. European Journal of Entomology 93, 369-382. http://www.eje.cz/pdfs/eje/1996/03/09.pdf

Day, K. R., Ayres, M. P., Harrington, R. & Kidd, N. A. C. (2010). Interannual dynamics of aerial and arboreal spruce aphid populations. Population Ecology 52, 317-327. http://link.springer.com/article/10.1007/s10144-009-0190-0#page-1

Gillette, C. P. & Taylor, E. P. (1908). A few orchard plant lice. Colorado Agricultural Experimental Station Bulletin, 113, 1-47.

Griffths, E. &Wratten, S. D. (1979). Intra-and inter-specific differences in cereal aphid low temperature tolerance. Entomologia experimentalis et applicata 26, 161-167. http://onlinelibrary.wiley.com/doi/10.1111/j.1570-7458.1979.tb02912.x/abstract

Knight, J. D. & Bale, J. S. (1986). Cold hardiness and overwintering of the grain aphid Sitobion avenae. Ecological Entomology 11, 189-197.

Leather, S. R. (1980). Egg survival in the bird cherry-oat aphid, Rhopalosiphum padi. Entomologia experimentalis et applicata 27, 96-97. http://onlinelibrary.wiley.com/doi/10.1111/j.1570-7458.1980.tb02951.x/abstract

Leather, S. R. (1981). Factors affecting egg survival in the bird cherry-oat aphid, Rhopalosiphum padi. Ent omologia experimentalis et applicata 30, 197-199. http://onlinelibrary.wiley.com/doi/10.1111/j.1570-7458.1981.tb03097.x/abstract

Leather, S. R. (1993). Overwintering in six arable aphid pests: a review with particular relevance to pest management. Journal of Applied Entomology 116, 217-233. http://onlinelibrary.wiley.com/doi/10.1111/j.1439-0418.1993.tb01192.x/abstract;jsessionid=9FC2ED8174E96317F192CF42A19092FE.f03t03?deniedAccessCustomisedMessage=&userIsAuthenticated=false

Strathdee, A. T., Howling, G. G. & Bale, J. S. (1995). Cold hardiness of overwintering aphid eggs. Journal of Insect Physiology 41, 653-657. http://www.sciencedirect.com/science/article/pii/002219109500029T

10 Comments

Filed under Aphidology, Aphids

The Curious Case of the Shark-finned Aphid

The large (giant) willow aphid, Tuberlolachnus salignus, is, in my opinion, one of the world’s greatest unsolved mysteries.  This aphid is sometimes regarded as being the largest aphid in the world.  It can reach a length of 5 mm, can weigh up to 13 mg as an adult and the new-born nymphs weigh about 0.25 mg (Hargreaves & Llewellyn, 1978).  You can get an idea of how big it is from the picture below.

willow aphid on finger

http://www.rothamsted.ac.uk/PressReleases.php?PRID=100

This is pretty big for an aphid, although not quite as big as one of my former PhD students (Tilly Collins) liked to pretend!  The picture below used to appear on her website and was the envy of a number of Texan entomologists.  Tuberolachnus salignus, as you might expect, since it feeds through the bark and not on leaves, has rather a long set of stylets, up to  1.8 mm, more than a third of it’s body length (Mittler, 1957).

tilly on aphid

This picture emphasises the first mystery: what is the function of the dorsal tubercle, which so closely resembles a rose thorn, or to me, a shark’s fin.  Nobody knows.  Is it defensive? Unlikely, since T. salignus being a willow feeder is stuffed full of nasty chemicals and very few predators seem to want, or be able to feed on it.  They feed in large aggregations on the stems of their willow tree hosts and can have serious effects on tree growth (Collins et al., 2001).  As the aphids produce a lot of honeydew, they are often ant-attended  (Collins & Leather, 2002) and these also deter potential predators.  In fact the aphid colonies produce so much honeydew in the summer that they attract huge numbers of vespid wasps that are in search of energy-rich sugar sources at that time of year.  These too are likely to make potential predators and parasitoids think twice about approaching the aphids.

Tuberolachnus

Photograph courtesy Dr Tilly Collins

The wasps also cause a problem for researchers and when Tilly was doing her PhD, she used to have to confine her fieldwork to those times of day when the wasps were not around.   In addition, if you crush one of the aphids you will discover that it stains your fingers bright orange and that this stain will last several days if you don’t try too hard to wash it off.  If you get this aphid ‘blood’ on your clothes they will be permanently marked and Tilly used to say that she ought to be paid an extra clothing allowance.

Tuberolachnus salignus, is as far as we can tell, anholocyclic, no males have been recorded and no matter how hard people have tried to induce the formation of males and sexual females, they have not been successful.  This is however, not the second mystery.  The mystery is that every year, in about February, it does a disappearing act and for about four months its whereabouts remain a mystery (Collins et al., 2001).  So we have an aphid that spends a substantial period of the year feeding on willow trees without leaves and then in the spring when most aphids are hatching from their eggs to take advantage of the spring flush, T. salignus disappears!  Does it go underground?  If so, what plant is it feeding on and why leave the willows when their sap is rising and soluble nitrogen is readily available?

So here is a challenge for all entomological detectives out there.  What is the function of the dorsal tubercle and where does T. salignus go for the spring break?

Truly a remarkable aphid and two mysteries that I would dearly love to know the answers to and yet another reason why I love aphids so much.

Collins, C.M. & Leather, S.R. (2002) Ant-mediated dispersal of the black willow aphid Pterocomma salicis L.; does the ant Lasius niger L. judge aphid-host quality. Ecological Entomology, 27, 238-241. http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2311.2002.00390.x/full

Collins, C. M., Rosado, R. G. & Leather, S. R. (2001). The impact of the aphids Tuberloachnus salignus and Pterocomma salicis on willow trees. Annals of Applied Biology 138, 133-140 http://onlinelibrary.wiley.com/doi/10.1111/j.1744-7348.2001.tb00095.x/abstract.

Hargreaves, C. E. M. & Llewellyn, M. (1978). The ecological energetics of the willow aphid, Tuberolachnus salignus:the influence of aphid Journal of Animal Ecology, 47, 605-613. http://www.jstor.org/discover/10.2307/3804?uid=3738032&uid=2&uid=4&sid=21101920521473

Mittler, T. E. (1957). Studies on the feeding and nutrition of Tuberolachnus salignus (Gmehn) (Homoptera, Aphididae). I. The uptake of phloem sap. Journal of  Experimental Biology, 34, 334-341  http://jeb.biologists.org/content/34/3/334.full.pdf

Other resources

http://influentialpoints.com/Gallery/Tuberolachnus_salignus.htm

http://www.nhm.ac.uk/nature-online/life/insects-spiders/common-bugs/aphid-watch/

4 Comments

Filed under Aphidology, Aphids, EntoNotes