Thursday, September 30, 2010

Meadow Brown Maniola jurtina

I am an amateur naturalist trying to identify and learn something about, everything living in my garden.

At the risk of butterfly-blog-overload ("Impossible!" I hear you cry) photo 1 follows on from my last posting and shows a Meadow Brown (Maniola jurtina). The photo was taken late last summer.

The Meadow Brown is fairly easy to identify, though it is worth checking you are not looking at a Gatekeeper (see my posting here) or Ringlet (some photos here).

My specimen here is tattered and faded - not uncommon for the Meadow Brown in late summer. Earlier in the season the upper parts of the wings would have been warm orange.

As with my Red Admiral last time, most of what I've learnt about my butterfly is taken from the splendid new book The Butterflies of Britain and Ireland (Jeremy Thomas and Richard Lewington, British Wildlife Publishing). Unlike many guidebooks, which merely supply you the name and a few scant details (foodstuff etc.) for your specimen, this book sets out to survey the literature and provide a scholarly essay on the natural history of each butterfly individually (not unlike what I aspire to do on my blog, though I don't for a moment pretend to the same levels of completeness or professionalism).

The Meadow Brown turns out to have a particularly rich history of scientific study. In particular it was extensively studied in the 1950's by the famous lepidopterist E.B. Ford and co-workers who were attempting to bring a new, quantitative understanding to genetics and evolution. Butterflies and moths make very good subjects if you want to study evolution: Their lives are relatively short thereby permitting one to follow some feature of interest across multiple generations. And at the same time, variations in their colourful wing patterns give you a very obvious and visible 'signature' that you can set about trying to relate to their genetic makeup.

Ford and others were interested in a wide variation that occurs in the number and spacing of some black spots that appear on the underwings of Meadow Browns. Unfortunately my Meadow Brown wouldn't stay still long enough for me to get a non-blurred photo of these but you can just about make out some spots towards the bottom of the wings in photo 2 (click to enlarge).

At this point I can't resist a small digression to talk about about E.B. Ford. A professor at Oxford University, by many accounts Ford seems to have been a somewhat 'difficult' character. He seems to have been not at all fond of women. He campaigned strongly against their being accepted to the then, all-male, college of All Souls. I also recall hearing somewhere he once refused to give a lecture on the basis that only females had turned up and that therefore there was no one 'worthy' to receive it! (I should add that I have failed to find a reference on the web to back-up this second story. I hope I am not falsely maligning Prof. Ford by it. If someone tells me it's incorrect I'll certainly take it down).

I have not found any free online archive of Ford's papers (anyone?). Whilst searching however, I did find an excellent and comprehensive archive of the papers of Ford's long-time co-worker R.A. Fisher here. (The good people of the University of Adelaide seem to be suffering from the strange delusion - shared by too few UK universities and institutions- that having presumably paid for some piece of university research in the first place, tax payers should get the chance to read the results without having to pay a second time to some private journal publishing house for the privilege!)

Anyway, getting back to the Meadow Brown. Through their work, Ford and others discovered some intriguing and puzzling trends in the wing-spot variation of this insect. They discovered, for example, that the typical spot pattern of Meadow Browns on small islands differed from that on larger islands. The question (unanswered at the time) was why?! What were the evolutionary causes and benefits driving this variation?

As the book above explains, answers only really emerged much later. The studies by Paul Brakefield were particularly important (you can find one of his papers here). It has become clear that spot variation is linked to habitat, in particular the extent of the ground-cover available in some region. Butterflies living in an area with lots of ground cover (long grass) can spend a lot of their time hidden away. For these butterflies, lots of spots would be a positive hindrance - if anything likely to 'blow their cover' to predators. Butterflies from areas with lots of long grass tend to lack lots of small spots therefore. They retain the big 'eye spots' seen in photos 1 and 2, but when resting in deep grass keep these hidden away behind their lower wings, bringing them out only as a 'startle measure' to frighten predators if they are attacked (I spoke more about eyespots here).

On the other hand, butterflies living in areas of sparse, grazed, or stunted vegetation (a small, wind-swept island as in Ford and others' study above for example) are forced to spend much of their time 'out in the open'. Such butterflies tend to have a lot of small wing spots. The reason is that these act as an 'always on' predator defence; An attacking bird is drawn to peck at the black spots on the 'expendable' wing tips, reducing the chance that the insect's precious head or body will suffer the first attack and thereby giving the butterfly the chance to escape attack with only minor damage.

There is much more than could said, especially about some further differences between male and female Meadow Browns. The former need to spend more time 'on the wing' and hence benefiting from some further differences in spot pattern. Since the authors above have already done it so much better than I might howver, I'll stop here, refer you to their book, and, apropos of nothing, end with a quote from the great P.G. Wodehouse:

The least thing upset him on the links. He missed short putts because of the uproar of butterflies in the adjoining meadows.

Saturday, September 25, 2010

Red Admiral Butterfly Vanessa atalanta

I am an amateur naturalist trying to learn something about everything living in my garden.

Taken last summer, photo 1 shows a butterfly basking in the sun on my garden table. There's no mistaking it as a Red Admiral (Vanessa atalanta).

What I have learnt about Red Admirals I have got from reading my newly acquired copy of The Butterflies of Britain and Ireland (Thomas and Lewington, publ. British Wildlife Publishing). This is a major new work that I can't recommend too highly for the interested amateur. All 72 'properly recognised' species of UK butterfly, each copiously and beautifully illustrated as egg, adult, caterpillar and chrysalis, and each with a full and scholarly essay on its natural history.

In common with the Painted Lady I blogged here, the Red Admiral undergoes a remarkable migration. Red Admirals overwinter in Southern Europe, not as adults, but as caterpillars, maturing slowly in the cool Southern winters. In early spring the (by then) adult Admirals start to fly North. Some will fly as far as Scandinavia.

When they arrive at a suitably Northern destination, the males set up territories on high ground where they mate with females which go on to lay their eggs, singly, on plants such as nettle (see my posting here). Eggs hatch after about a week and the emerged caterpillers mature over about a four week period. The caterpillars carry a dozen or so sets of bristles along their bodies and come in two forms: black and green. They have the evolved the remarkable trick of constructing a 'tent' of leaves, sewn together with silk (there's a picture here). Sitting inside they can munch away out the sight of predators. The caterpillars pupate in an attractive grey and yellow-spotted chrysalis to emerge to later as the beautiful butterfly of photo 1. Around October, as the weather cools, these adults fly to back to Southern Europe and the cycle begins again.

The book above mentions a fascinating puzzle for a population of Scandinavian Red Admirals. Leaving Scandinavia at the end of summer the adults start out by flying due South. After a time however, they reach the coast in Southern Sweden. At this point the butterflies 'cleverly' turn West in order to minimise the distance they need to fly across open sea before reaching land again at Denmark. From Sweden, the coast of Denmark is 24km away and only barely visible to human eyes in a fine day. How the butterflies are able to detect it and know to turn West therefore is a puzzle. It is speculated that they may be making use of an ability of many insects have to see the 'polarisation state' of light. 'Polarisation' is a property of beams of light that humans can't see, but suffice to say land and water can affect it in different ways. It is theorised the migrating Scandinavian Red Admirals are using this to aid them in detecting land at a distance. This appears to be unproven however. Another of nature's mysteries!

Friday, September 17, 2010

A lichen: Lecidella elaeochroma

I am an amateur naturalist trying to discover everything that lives in my garden.

Once upon a time there was a large, upright apple tree in my garden. And then quite suddenly, one night, there wasn't!

What happened is a story most relevant for this blog...but one for another time. For today let me remark only that this calamity gave me an unprecedented opportunity to inspect my tree's upper branches for one of my favourite lifeforms - the lichens.

Photo 1 shows a lichen new for this blog (the grey smudge that is, the yellow is Xanthoria parientina I've blogged previously). Photo 2 shows a closeup of my lichen's areolate thallus (=cracked surface) and black, lecideine apothecia (= fruit bodies - see my artwork and explanation here).

Despite my fondness for lichens I am very far from being an expert. One problem facing the amateur is that many species look rather similar to the eye. Some are all but impossible to separate by anyone who does not happen to possess a forensic chemistry laboratory. (This is not a joke. It is not uncommon for the professionals to turn to e.g. chemical chromatography in pursuit of accurate identifications of lichens).

Fortunately there are a few 'tricks' available to the amateur. One is to observe your lichen under UV light. This is not as difficult as it sounds. In my case a battery-powered banknote reader from a 'pound store' (that's 'dollar shop', '100yen shop'... to those of you reading overseas) yielded the rather lovely result at the bottom of photo 2. The point is that had my lichen been the superficially similar Fuscidea cyathoides (picture available here), also occasionally found on wood, then UV light wouldn't produce the glow seen here. In the jargon, F. cyathoides is 'UV-' . By comparison, as I learnt from to my copy of Lichens (Dobson, Richmond Publ.) the common UK lichen Lecidella elaeochroma is 'UV+ orange' - clearly a good fit and my identification for today (as always I'm happy to be corrected).

I have mentioned previously a question that I have puzzled over regarding lichen: My (decidedly amateur) understanding of evolution has always been that, over time, it drives species towards adopting the optimal form for surviving in their environment. What has puzzled me is how then, it can be commonplace to see lichens with really quite dissimilar features occupying the same environmental niche. Inspect a few twigs on a tree and it's really not uncommon to find, side-by-side, both crustose (pancake-like) lichens, and, as here say, the bright yellow, foliose (=leafy) lichen X. parientina. To survive on wood, how can it be 'evolutionarily optimal' to be a bunch of bright yellow flakes, and optimal to be a grey pancake. Surely one ought to have 'won the argument'? It was satisfying recently therefore to come across a section in the book Introduction to Bryophytes (Vanderpooten and Goffinet, publ. Cambridge) that I think has given me the inkling of a solution to my confusion.

The book describes how some species of moss have become expert in seizing the opportuntity to colonise fleeting, virgin, environments. A newly appeared patch of burnt ground after a forest fire for example. Clearly being 'first moss on the scene' has the benefit you will enjoy the resources of your new home free from the pressure of competition. There is a price to pay for such a lifestyle however. To succeed at rapidly detecting newly emerged environments requires that you to put a great deal of your energies into sending out countless 'scouts' (a.k.a. spores) to explore your environs. By definition, if you're putting your energies into volume spore production, you are precisely not putting them into your own growth (producing lots of leaves etc.). Such 'fugitive mosses' therefore tend to be slight, quick-to-mature, normally annual plants, producing large numbers of small 20um spores.

Now 'fugitive' is not the only survival strategy amongst mosses. Enter the dominants. Dominants aim to out-compete other mosses for light and nutriants by growing faster and larger. This is a perfectly reasonable strategy, but again has its limitations. By investing a large proportion of their energy into the rapid growth of leaves etc. such mosses are left with little energy for the production of spores. Dominants then, will be less successful at rapidily discovering new areas, and tend to be larger, perennenial mosses with fewer spores. This is far from the complete story. As well as doimants and fugitives, the book above goes on to discuss the strategy of 'colonists', 'perennial stayers' and 'annual shuttles'. I have not found any freely available articles discussing similar issues for lichen (anyone?), but I think its not unreasoanble to suppose some similar ecology might hold for these fellow tree- and rock-dwellers.

All of which brings me back to my puzzle of how evolution can have a arrived at two such different forms (body shapes and colours) as optimal solutions for lichens living in the same place (a twig). I don't pretend a complete answer, but I feel I may have started to get an inkling of understanding. I think my confusion likely stems from woolly thinking on my part, namley, in erroniously imagining that evolution is about optimising a creature's form to fit a place. The more I've thought about the moss examples above however, the clearer it seems to me now that it is not 'body shape' that evolution is working to optimise, but rather the whole organism. That is, not merely its shape and colour, but rather the totality of its life cycle and survival strategy. Furthermore it is not sufficient to think of a lichen's 'environment' as being merely some unchanging point in space (the surface of a twig, say). This misses the very significant additional fact that our twig is subject to an annual cycle of dramatically changing seasons and that it itself is a growing, changing, transitory thing. At the risk of sounding too poetical, thinking of the lichens on my tree now I begin to get an image of a complex spaghetti of life histories and strategies at work. It is facile to try to ask whether 'yellow and flaky' is a 'better or worse' body shape for living on twigs than 'flat and grey'. Instead, each lichen will be following some complex survival strategy with multiple factors and tradeoffs. Viewed in this way, although two lichens have met on a twig in photo 1, viewed over extended time, the 'trajectory' of their lives is no doubt entirely different. The forms they have will be because these are the forms that best befit them to their individual, distinct, extended, life styles.

My great pleasure in researching this blog is that through it my view of my garden grows richer all the time. To my mind, no one has said it beter than Martin Luther

For in the true nature of things, if we rightly consider, every green tree is far more glorious than if it were made of gold and silver.

Saturday, September 11, 2010

An Ichneumon wasp - Amblyteles armatorius

I am an amateur naturalist trying to learn something about everything living in my garden.

Hello! After a goodly absence I am back with some more of my garden wildlife. I hope there may be one or two of you out there still reading. Certainly my garden has not run short of new lifeforms to offer. Despite over a 100-species blogged so far, I have a long backlog of additional finds with more turning up all the time.

Photo 1 shows a magnificent insect I spotted resting on my hedge in late-summer of last year. The body was around a cm in length. Based on some similar images on the web I'm identifying it as an Ichneumon wasp - Amblyteles armatorius.

With tens-of-thousands of species of Ichneumon wasp worldwide and about 3200 in Britain alone, definitively identifying Ichneumons is a job for the specialist. Dr Gavin Broad is one such and has helpfully made available an online British checklist and a key to the sub-families of Ichneumonidae. You can download the entire 380-odd pages of the 1903-published Ichneumonologia Brittanica for free here. For any naturalist willing to grapple with the subject however, a supreme example of what can be achieved (and surely a candidate for "all-time greatest garden study") is given by Jennifer Owen. Her book, The Ecology of a Garden (Cambridge Uni. Press) records 15 years of painstaking cataloguing of the wildlife in a UK garden. During her studies Dr Owen discovered no fewer than 529 species of Ichneumon of which 15 were new to Britain and a staggering 4 were new to science!

From the comments above it will be understood my amateur's identification, based on a photograph alone, of my wasp as A. armatorius is to be treated with caution. It is certainly not the only European black -and-yellow striped Ichneumon as can be seen, for example, from the photo's here of species such as Ichneumon stramentor, I. xanthorius, Eutanyacra crispatoria and Diphyus quadripunctarius. For now I'm sticking with A. armatorius, as some of these others have yellow-striped antennae and other small differences, but I'm happy to be corrected by any of the experts out there.

Sadly, I have been able to uncover rather few details of the natural history of my Ichneumon. I have learnt that it is fairly common in the UK and the sole species in the genus Amblyteles. Adults apparently feed on pollen, that of umbellifers being a common target. In common with many other ichneumon's, the larvae are parasites of caterpillars, one target moth being The Yellow Underwing (Noctua pronuba). The larvae hatch inside the caterpillar and devour it from the inside. Other target moth species besides the Yellow Underwing are variously stated for A. armatorius. The scientific paper by Rolf Hinz (Entomofauna, 6(8), 1985, pp.73-77) disputes these claims however.

The paper above is in German incidentally, which is unfortunate if like me, you don't speak the language! (I found a free online copy of this paper some time ago, but have entirely failed to relocate it since. Anyone?). Since this was one of the very few learned articles I came across on A. armatorius however, I was determined not to be put off and came up with the idea of running the German text through Google's free, online automatic translation service. The results of computer translation are not always transparent. A German sentence that, in the original, I take to say something along the lines:
"I'm grateful to Messrs. G. and E. MannBausch Heidt of the Künanz Upland Bird-research Centre for supplying me with specimens"
gets translated as
"Messrs. G. and E. Mann Bausch
Heidt from the research Künanz bird-house in the mountain, the procurement of the material allowed, thanks.
Nevertheless, with patience it's generally possible to get the gist and I'll certainly consider using this approach in future.

I appear to have digressed! When starting today's posting it had been my intention to say something on the amusing topic of the religious debate sparked amongst Victorians naturalisists by the life-style of the Ichneumonidae. Since I have written enough for now however, and since, with another 3000-odd British Ichneumonidae out there, I feel confident I will have other chances to revisit this fascinating family of insects in the future, I will leave my somewhat cryptic last sentence hanging in the air and bid you farewell for now.