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.

1 comment:

legomaster said...

I can verify the comment about EB Ford as the wife of a friend who was a student at Oxford at the time suffered this treatment.

It is also quoted in Of moths and men by Judith Hooper.