Transformer

When our kids were small they collected toys called transformers, which were model vehicles that turned into menacing robots when you pulled, twisted and rotated their articulated parts. They were marvels of imaginative, miniature engineering but couldn't hold a candle to this wonderful natural transformer - a cabbage white pupa, which I found under the rim of a seed tray in the greenhouse yesterday. Insect metamorphosis is one of the most mind-boggling developmental transformations in the natural world.

Inside this pupal case the caterpillar - an insect eating machine that chewed holes in our broccoli leaves is turning into a 'soup' and reorganising itself into a delicate, winged, nectar-feeding cabbage white butterfly that will emerge next spring.

The caterpillar has pupated fairly recently - over the winter its green shade will turn to pale brown. If you look closely, about one third of the way down the image you can see the silken halter that the caterpillar spun to attach itself to the seed tray - it's last act as a caterpillar.

Click here to see a great YouTube movie of a large white butterfly hatching from its pupal case.

You can read about the biology of insect metamorphosis by clicking here

Berries

This must surely be the best year for hedgerow berry crops in recent memory. Last year there were very few berries available when the first of the winter flocks of redwings and fieldfares arrived, but this year the fieldfares that we saw pouring into Teesdale on Saturday were greeted with an almost inexhaustible supply. 

Hawthorn

Hawthorn

Rowan

Rose hips

Mild, wet weather has encouraged fungal growth, causing many of the rose hips to begin to rot, so their juices are attracting the last of the red admirals.

Long term project ...

There is a saying amongst foresters that 'you should plant as though you are going to live forever'. Sound advice, since most forest trees have natural life spans that far exceed ours - provided that the trees can survive hazards like rabbits, fungal diseases, deer, climate change, gales or developers building more out of town shopping malls.

For any tree planting enthusiast who takes a really long-term perspective and wants to leave a natural legacy, now is the perfect time to plant an oak tree........ 

.......... because acorns germinate almost as soon as they fall from the tree, producing a sturdy white root that spears down through the leaf litter and continues to grow through the milder days of winter. Then, in spring, the first leafy shoot appear. So pot up a few germinating acorns now and a successful start for the seedlings is almost guaranteed. 

It's a 'mast year' for oaks here, with thousands of acorns on the ground. Most will be eaten by pigeons (I once found a dead one with 23 in its crop), deer and mice but the lucky ones might be carried away by a jay from the shade of the parent tree and buried for future use when food is scarce. The jay will probably forget where it cached its winter food supply - and all the while the buried acorns will be sending down those roots, ready for the start of their first growing season. Come to think of it, jays probably give more oak trees a good start in life than we humans do.

The Magic of Mushrooms

Part of the magic of toadstools is the way in which they suddenly appear in unexpected places. During the current spell of wet weather these blewits Lepista personata have erupted through the soil under a privet hedge in our front garden. It's the first time I've ever seen them in the garden, although about twenty years ago I deliberately introduced some onto an old compost heap, where they produced a crop for a couple of years. 

I'm tempted to cook them because blewits are considered to be good eating by mycophiles, although they also have a reputation for triggering allergic reactions in some people. 

I have a fascinating copy of the second edition of a book published in 1847 by Charles David Badham M.D. entitled A Treatise on the Esculent Funguses of England containing an account of their Classical History, Uses, Characters, Development, Structure, Nutritious properties, Modes of cooking and Preserving etc., - all described in 152 anecdote-filled pages and illustrated with 12 hand-coloured plates. Having travelled in Europe and seen fungus markets and the enthusiasm for eating wild toadstools in Italy, Badham became a passionate advocate of toadstools as food for the poor and described the purpose of his book as being "to furnish the labouring classes with wholesome nourishment and profitable occupation". 

In Badham's day blewits were rather poorly known in England and were just beginning to appear for sale in Covent Garden markets. He gives a recipe for collecting and preparing them, which goes as follows:

"... it is a fine firm fungus with a flavour of veal, like which it is dressed en papillottes with savoury herbs and the usual condiments, and the more highly seasoned the better"

Unfortunately he also says " As the Blewitt is apt to imbibe in wet weather a great quantity of moisture it should not be gathered in rain when water-soaked". Since there's not much sign of the rain stopping, they may no longer be a "fine firm fungus" by the time they've dried out enough to pick, so maybe I'll have to leave them to the maggots that often infest old blewits.

Viaducts

Yesterdays's Guardian Country Diary described a walk around the Cumbrian market town of Kirkby Stephen. All the pictures below enlarge if you double-click on them.

This path out of the town takes you through the village of Hartley and then onto the disused South Durham and Lancashire Union Railway, where freight trains once hauled coal from the Durham coalfields and haematite ore from Cumbria across the notorious Stainmore Summit - the highest railway line in England. Now the section of the track bed that passes through Kirkby Stephen is a popular public footpath through wonderful scenery.

The line and its viaducts was engineered by Sir Thomas Bouch and three of his fine viaducts, including the Merrigill viaduct and the Podgill viaduct (above), are now in the care of the Northern Viaducts Trust. They seem to be as sound as they were on the day that they were built, unlike Bouch's Tay bridge which collapsed, taking a train and 75 passengers with it and inspiring what is often described as the worst poem in the English language, The Tay Bridge Disaster by William McGonagall

The line was originally single track but was eventually doubled - when you stand under the viaduct you can see where it was widened - the size of the blocks and their patterns of construction are different.

This is the view down from the Podgill viaduct into the valley cut by Ladthwaite beck, on a fine spring day earlier this year.

The viaduct casts an imposing shadow...

...... and provides a kestrel's-eye fine view to the north of distant Cumbrian fells, in between showers and rainbows.

It's a shame that these rural railways have gone but the old track beds are a superb legacy, providing rural walks with gentle gradients that accessible to all.

Part of this route forms part of a poetry path, with verses carved into local sandstone and limestone at intervals along the route.

This is the view towards the fells to the south as the path nears Kirkby Stephen.

At this point you can choose to walk on, to reach the finest of the three viaducts at Smardale Gill, or you can cross the river Eden where it forms a series of waterfalls at the Millenium Bridge.

From there the route back into Kirkby Stephen follows foot-worn paths through farmland and woodland where you can sometimes see red squirrels and which have fine displays of wild flowers in spring.

The route back involves recrossing the river Eden at this point, where it's shallow and stony and is a perfect spot for watching dippers all year-round. There are often herons here too ....

... which is why the last of the twelve  poems carved in stone, on across three rocks, reads as follows:

"There sails the heron / drawing behind him a long / wake of solitude"

On cue, just as we reached these stones, a heron did indeed rise from the Eden further downstream.

You can find more information about the viaducts and footpath maps at the Northern Viaducts Trust website and also in their downloadable brochure

Condemned to life in total darkness beneath the Stadium of Light

I found these two photos amongst colour transparencies that I took back in 1994. They are of a little gammarid shrimp, similar to the species that live in ponds and streams everywhere, but this one has a very unusual story attached to it.

One day in late spring 1994, just before Monkwearmouth colliery, also known as Wearmouth colliery (see photos here), was due to close, I had a telephone call from a journalist on the Northern Echo who had been talking to some of the miners who were about to be made redundant. This was more than just another pit closure: Monkwearmouth was the last deep mine to close in the Durham coalfield and had been there for 178 years. It had once been the deepest coal mine in the world.

The miners told a story about shrimps that lived in pools of water at the bottom of the mine. The crustaceans had most likely been taken down there in water for the pit ponies and were well known to miners who had worked the seams in  the oldest shafts. 

At that time the deepest hole in the ground I've ever been down was at Cheddar caves, so the offer of a trip down to the bottom of the mine to collect some shrimps was too good to miss. At the bottom of the old shaft that had been abandoned for many years we found the shrimps living in the coal dust in pools of water, where they most probably fed on bacteria that lived on sulphur and fungi that lived on rotting wood. If you look at the photos above you can see grey coal dust in their digestive tracts. They had an aversion to light and when the beam of our helmet lamps fell on them they scuttled down into coal dust slurry. If you look at the enlargement of the eye (below) you can see that it had only a few, rather disorganised lenses, compared with a crustacean that lives in daylight like this one - these troglodyte shrimps may have been on their way to losing their redundant power of sight. 

We brought a couple of buckets of them up to the surface and kept them in a tank in my laboratory at Durham University. We had hoped to go back for more but British Coal demolished the winding tower with indecent haste before we could mount another expedition.

 This is the piece about the collecting trip that I wrote at the time for the Guardian Country Diary:

We entered the rusty cage of B Pit at Monkwearmouth colliery on a rescue mission, in search of an underground colony of shrimps that has persisted there since the shaft was opened in 1841. After a 12-minute descent we jerked to a halt 1080 feet underground, stepping out into caverns lined with crystals that glistened in our lamp beams. 

We found the colony, in a small black lagoon at a tunnel entrance littered with rusty picks and blocked by a collapsed roof. The half-inch-long shrimps dashed across the surface, thrashing through pools of light from our helmets and disappearing into the black ooze. These tiny crustaceans, familiar to generations of miners, live in a seasonless world of perpetual darkness and constant temperature, probably feeding on bacteria that grow on sulphur in the coal. Kenny Drysdale, the shaftsman who led us to them, told us that miners once supplemented the shrimp' diet with bread crusts. Within a few minutes we had scooped up as many animals as we could catch. The only other sign of life was a spider's web. Its builder, long since gone, must have been drawn down by the shaft ventilation system. 

In the tunnels we passed massive, rusty iron grates where controlled fires had once burned, to draw in cold air from above in the wake of their rising column of heat. Then, this pit must have resembled a scene from the underworld. The names of generations of miners were chalked or scratched on walls and beams in silent tunnels strewn with rusty pulleys and rails, thick with dust, shored up by props and baulks and boards and sealed with doors that hung from creaking hinges. 

Back on the surface, the rescued shrimps now live in my laboratory, thriving in an aquarium. Soon the unlucky ones will be sealed underground for ever, when the life of the colliery finally expires. Yesterday, I dropped a crust of bread in the tank. The shrimps swarmed around, tore crumbs off and retreated to their corners, just as Kenny said they would.

June 1994.

There's a rather sad postscript, which leaves me with an abiding sense of guilt. Soon after we brought the shrimps up our new laboratories at Durham University were completed and we had to move out of the old ones in a tearing hurry so that builders could move in. The shrimp tanks were due to be the last items to be moved but somehow someone mistook the tanks of grey water and coal slurry for rubbish to be disposed of, and tipped the water down the drain and threw the old tanks in the skip. So all that remains are a few specimens preserved in alcohol and, perhaps, the descendants of some that I had released into our garden pond.

Almost as soon as the pit was demolished and the site was cleared work began on  Sunderland Football Club's new Stadium of Light on the surface, immediately above. The population of shrimps is still down there, 1000 feet underground, nibbling away at fungi growing on rotting pit props and feeding on the sulphur bacteria, and will now remain there, in total darkness, for all eternity.

A Rapidly Evolving Botanical Hooligan......

Invasive species often hit the headlines here in Britain but we have exported a few of our own too, that have created ecological chaos in other countries. One of the most notorious is purple losestrife Lythrum salicaria. Here in the UK it's a well-behaved wetland species and the Wildlife Trusts' web site describes its 'impressive spikes of magenta flowers' as a 'valuable source for long-tongued insects like bees, moths and butterflies, including brimstones, Red-Tailed bumblebees and Elephant hawk-moths' 

In our garden it's a star performer in a small, boggy area where it's particularly popular with hoverflies ...

.... that feed on its readily accessible pollen. It does have a very high potential seed output, so most gardening experts advise removing the dead flower heads before they can set seed but in the wider countryside it's a well behaved component of our native wetland flora and is sometimes deliberately introduced to increase botanical biodiversity, as it has been .....

...... here along the Ouseburn in Newcastle, bringing a splash of colour to what was once a heavily industrialised and polluted environment.

However, when it travels abroad it develops hooligan tendencies, spreading rapidly and outcompeting native vegetation. Since it was first introduced into the New World in the New England area, probably sometime around 1800 in ships' ballast (and also deliberately because of its uses in herbal medicine) it has run riot, with a very rapid period of range expansion in the 20th. century. It's now the worst invasive plant species in wetland ecosystems throughout the eastern seaboard of the US and in Canada. You can read a detailed account of the history of purple loosestrife in North America and Canada by clicking here

Several theories have been advanced to account for its invasive behaviour, one of the most important being that when it travelled across the Atlantic it left its natural pests and diseases behind, so that it could reach its full reproductive potential. A single vigorous plant can produce fifty flowering stems that dominate surrounding vegetation and produce around two million seeds - which are carried far and wide by wind and water - annually. Once established in its new environment, and free of pests and pathogens, purple loosestrife no longer needed to devote energy to defending itself and could commit all its resources to reproduction.

Recently a research paper in the journal Science has provided another insight into the invasive tendencies of this New World immigrant. Multiple introductions of purple loosestrife produced a genetically variable population that has rapidly evolved ecologically adapted populations across a very wide geographical distribution. Plants that have colonise Canada, where the growing season is short, have evolved to flower early to maximise their seed output. Those that have migrated into the warmer southern United States have evolved to flower later and devote more of their resources to tall, vegetative growth before they switch into flowering mode. The authors of the research reciprocally transplanted sample plants from the extremes of their range to confirm the evolution of this rapid local adaptation; predictably, early bloomers from the north were less competitive in southern locations, and vice-versa.

One of the most interesting wider implications of this research is that it highlights the ability of plant species like purple loosestrife, that are genetically variable, that have a vast seed output and that reproduce rapidly once established, to evolve adaptations to new environments very quickly. Now that we are in a period of rapid climate change, it does give an indication of the ability of some plants to use their pool of genetic variation to exploit changing environments by evolving new adaptations, and it underlines the importance of maintaining genetic variability in plant species that might be vulnerable to climate change.


Source: Robert I. Colautti and Spencer C. H. Barrett (2013). Rapid Adaptation to Climate Facilitates Range Expansion of an Invasive Plant. Science 342, 364

A good beer guide for wasps .........?

In autumn, when wasps finish breeding, they turn their attention to anything sweet and often become a nuisance. One solution is to trap them in narrow-necked bottles container a mixture of jam and water - but there are other baits that can be used too.

Back in 2007 a researcher in the Czech Republic called Libor Dvorak tested out traps containing beer as a bait (he didn't mention which brand) and after trapping 3583 wasps of 8 different species at 131 sites across Europe, including several in Britain, found that three species including the common wasp Vespula vulgaris (above) were most prone to drowning in the traps. I suppose there are worse ways to go. If you want to read the original scientific paper you can download it by clicking here.

As far as I can tell, no one has ever followed up this research by testing whether wasps have a particularly preference for any type or brand of beer. Do they have a favourite tipple? Guinness? Fosters? Budweiser? Carling? 

Clearly there's scope for some important and original research here. Maybe drink 95 per cent of the beer in ten different bottles, then line the bottles up and see how many wasps end up in each bottle?v At 131 sites across Europe?

My kind of experiment.

Does a wood pigeon's breeding season ever end?

This mother and child combo turned up outside our living room window this morning. Wood pigeons have been breeding in the garden for several years, but I think this is the latest-ever squab. It must have left the nest during the gales and driving rain over the last couple of days, but seems to be in good fettle, pestering the life out of its mother.

More scenes from wood pigeon family life here.

The relentless rise of the wood pigeon as a garden bird has been a notable ornithological trend over the last decade. It's now the fifth most frequent bird species in gardens. In many ways wood pigeons are charming, especially during their courtship, but they are the bird equivalent of a Hoover on a bird table, gobbling up the food at a phenomenal rate. 

In praise of some non-natives

Wildlife gardening evangelists frequently exhort us to plant native species in our gardens - quite rightly, as there are indeed many native plants that are decorative and provide valuable resources for insects and their larvae. 

But when it gets to this point in autumn the choice of flowering natives is pretty narrow. There's ivy, which is certainly a terrific source of pollen and nectar for insects and also food plant for holly blue butterfly larvae, but that's about it  - other that a few late hogweed flowers and yarrow, which flower up until the first frosts but don't bring much colour to a garden.

So that's when Michaemas daisies Aster amellus, whose natural range extends across southern Europe into Asia, come into their own. Whenever the sun shines the Michlaelmas daisies in our garden attract a constant stream of visitors, including ....





.... hoverflies, like this Heliophilus pendulus

..........honeybees ......

.............. small tortoiseshells ............

.............and red admirals, all photographed in the space of a few minutes at the end of last week.

Marigold Calendula officinalis, which originated in southern Europe, provides similar services for butterflies throughout autumn.

Buddleia davidii, the famous butterfly bush from Central China and Japan, has - until recently - been a favourite amongst wildlife gardeners as a nectar source for butterflies, even though it usually finishes flowering long before the late autumn generation of small tortoiseshells, peacocks, red admirals and commas get into their stride. These days conservationists give B.davidii the thumbs down, on account of its invasive tendencies, but there is a much better Buddleia alternative - B x weyeriana, which is an interspecific hybrid between B.davidii and B.globosa and has very attractive pinkish-orange flowers and none of its parent's tendency to seed itself around prolifically. It's extremely hardy and continues to flower long after the first frosts, offering a 'last-chance saloon' for any insects that need to top up with nectar before going into hibernation.

Red Admiral hairy eyes

One of the pleasures of macrophotography is that you tend to notice things in the captured image that you'd never be aware of otherwise.

Until the colder weather arrived a couple of days ago we had several red admiral butterflies in the garden. I took some extreme close-ups of them, while they were feeding on ripe pears, and noticed in the images .....

.... that their eyes have this strange hexagonal pattern. Looking closer still, it's clear that .....

.... the eye surface is hairy and it looks like it's the pattern of hairs, located in between the individual ommatidia of their compound eyes, that is responsible for those large pale hexagons. A comparison with eyes of other common butterflies, like...

..... this small white, shows a pattern of darker patches on the eye but not a hint of hairiness around the ommatidia.

So I wonder what the hairs' function might be? Maybe they enhance flicker vision - the sensitivity of compound eyes to movement of objects across the field of vision............? 

Hairy eyes are not uncommon in insects - click here, for example, to see a scanning electron micrograph of a honeybee's hairy eye. Another possibility of that the hairy surface might stop pollen sticking to the eye surface in these flower-visiting insects.........

Hedges

Thursday's Guardian Country Diary is about hedges - well, about one old, overgrown hedge,  a favourite that has produced a spectacular crop of autumn fruits this year.

Most old hedges date from the period of the Enclosure Acts, when tracts of common land were enclosed, usually via the planting of hawthorn (aka quickthorn) hedges. The exceptions are much older assarts - remnants of ancient woodland around the edges of fields that were hacked out of the Wildwood by our distant ancestors.

Hawthorn is an ideal hedging plant- fast to establish, tolerant of cutting and forming a thick, stock-proof boundary if it's well maintained. So that it remains densely branched at its base. This was originally achieved by laying, a process that involved a great deal of skilled manual labour. The technique, which is seldom seen these days, is described and illustrated here.

Almost as soon as a new hedge was established it would have attracted birds that arrived to eat the hawthorn fruits and they in turn would have left seeds of other succulent fruited plants in their droppings, including ...

........brambles (this wonderful crop, beyond the reach of bramblers, was cascading down the overgrown hedge that's mentioned in the Country Diary), and also .......

.... elder, which has produced a massive berry crop this year.

Sloe (aka blackthorn) was occasionally used as a hedging plant but has the disadvantage that it spreads laterally into fields, via sharp-pointed suckers that grow from its spreading roots. On the other hand, those sloes are great for flavouring gin.

Like brambles, briar roses scramble up through hedges, using their thorns for support, adding to the autumn berry crop ....

.... along with bird-sown honeysuckle which twines around stems of supporting hedgerow shrubs, producing berries that blackbirds are very fond of .. and ....

..... often producing a few flowers right up until the first frosts.

So gradually planted hedges naturally acquire an ever-richer flora, together with herbaceous plants that used the hedge as a refuge from surrounding cultivation.....

........ along with a wide range of invertebrates, like this snake millipede that we found coiled up and asleep at the top of a tall brome grass stem in the hedge ....

............ and these nettle tap moths. They breed on hedgerow nettles and feed on hogweed flower umbels, that often continue to produce a few flowers and some nectar right up until the first frosts.

Sadly many old hedges have been grubbed out to enlarge fields. Some hedges are still being planted, like these that were planted in mitigation on land that had been opencast mined. They are mainly a double row of hawthorn, with a sprinkling of other shrub species like hazel, with a standard tree - usually ash - at regular intervals.

Annual mechanical cutting, with a tractor equipped with a cutter bar or a flail cutter, trims them into neat, uniform, dense stock-proof hedges but severely limits their value as a wildlife resource;the annual trim removesmost of the current year's grow that will bear the following year's flowers and fruit, so the value of hedges that are maintained like this is much less than a hedge like ......

........... this, which has been allowed to grow, has a broad margin and retains all its flowering potential, so that in summer ......

.......... it will look like this. Dense, overgrown hedges have the potential to act as wildlife refuges and wildlife corridors. 

It is important that hedges are maintained, otherwise they simply develop into lines of trees but cutting hedges rotationally on a three-year cycle, rather than annually, would greatly improve their value as cover for birds and mammals, providing a supply of pollen and nectar for insects and autumn fruits for birds and mammals.

Simply planting more hedges isn't necessarily a particular effective wildlife conservation measure, although it's better than nothing. It's the quality of hedges that really counts, and that depends on how they are maintained.