Saturday 22nd June 2013

Butterflies of the Bistort

Today’s target species were two veritable specialists, the Violet Copper, Lycaena helle, and the Bog Fritillary, Proclossiana eunomia. The larvae of both species feed (at least in this area) exclusively on the leaves of Bistort, Polygonum bistorta, a plant that grows in profusion in damp meadows in the region where I am currently located, in the Hautes Fagnes/Hohes Venn (or High Fens), in north-eastern Belgium. This is a wild area of peat bogs, extensive forests and open tussocky grassland, peaking at the highest point in the Benelux countries, at 694 metres. Just to the south is an extensive network of small streams, and along their valleys is where the most extensive areas of the beautiful pale pinkish blooms of Bistort can be found, along with their attendant butterflies.

A valley filled with Bistort, larval foodplant of the Bog Fritillary and the Violet Copper

Despite far-from-ideal weather conditions, it was not long before I was able to locate a single Bog Fritillary, trying to warm itself in the weak sunshine. The Bog Fritillary is superficially similar to other small fritillaries, including the Small Pearl-bordered, of which I later saw a few as well, but the black markings on the upperside are narrower, and there is a very faint suffusion of black scales across the entire upper surface, giving it a slightly dusty appearance. In addition, this species is less hyper-active than other similar fritillaries, which tend to race about, settling only rarely, whereas this species is much less flighty, and therefore easier to approach.

A male Bog Fritillary basking in the weak sunshine

After the short sunny spell that allowed me to see the Bog Fritillary, dark clouds began to move across the sun, but I just had time to locate one example of the Bog Copper, Lycaena helle, hunkering down among the vegetation, out of the strong wind that was whistling along the valley floor, stirring up the Bistort plants and making photography a challenge, to say the least.

A rather tired-looking Violet Copper

Unlike the Bog Fritillary, the Violet Copper emerges earlier in the year, and I was not sure that I would find one even disregarding the poor weather conditions, and I was pleased to do so, especially as the sun promptly disappeared and the rain began to fall, rendering butterfly observation out of the question, at least for a while.

Luckily, however, the wind was sufficiently strong as to blow the storm quickly through, and from then on the day turned into one of “pepper and salt”, with sunny spells interspersed with dark periods of drizzly rain, and always with that strong wind whisking across the valley floors.

It was not long before the sun reappeared, and with it several more Bog Fritillaries. While the upperside may be hard to distinguish from other small fritillaries, if one gets the chance to examine the underside, any lingering doubts are soon dispelled; the pattern on the underside of the hindwing is totally distinctive, with no silver spots and a row of small rings parallel with the outer margins; the Dutch name of this species, Ringoogparelmoervlinder, means ring-eyed mother-of-pearl butterfly, a highly appropriate name, except that unlike most other fritillaries, this species does not have the amazing mother-of-pearl-like silver spots so characteristic of the group.

A Bog Fritillary perched on a Bistort flowerhead, showing its characteristic row of open rings on the underside

From here the trail passed through a stretch of thicker pinewoods, where butterflies were not to be found, but just beyond was a much more open area of Bistort, interspersed with thistles, and some flower-filled fields in which I had high hopes of finding my third target species, the almost unimaginably beautiful Purple-edged Copper, Lycaena hippothoe. The flowerheads and grass were waving about vigorously in the gusting wind, making the search for butterflies even more difficult, but it was not long before I spotted a purplish shape fluttering through the grass stalks, and it turned out to be a newly-emerged, jewel-like male Purple-edged Copper. Photography was far from easy, but I did manage to obtain one passable shot before the butterfly was swept away in the wind and I lost sight of it.

A glowing male Purple-edged Copper

By now the weather was closing in again, and the return walk was marked only by around three handsome Large Skippers, Ochlodes venatus, darting along the verges of the trail through the pinewoods.

A bright, newly-emerged male Large Skipper

Skippers are known in Dutch as Dikkopjes, or fat-heads, due to their broad heads

Shortly before I reached the car, the route took me past a more sheltered, Bistort-filled clearing, where several more Bog Fritillaries were to be found, followed by one very ancient-looking Violet Copper, missing a large section from one of its hindwings, and probably not destined to last many more days.

The sheltered, Bistort-filled clearing

A Bog Fritillary, wings open to catch all the warmth it can obtain from the weak sunshine

The tired-looking Violet Copper, part of its hindwing missing

The Violet Copper, enjoying perhaps the last few days of its short spell as an adult butterfly

Many of the river valleys and Bistort areas here in eastern Belgium have been lost, partly due to agricultural “improvement”, and partly converted into intensively farmed plantations of young spruce trees, mainly for the Christmas tree market. However, in this particular area, strenuous efforts have been made to not only preserve the remaining habitat, but also to extend it. Long may these wonderful areas of marshland, dotted with the pink spikes of the Bistort flowerheads, remain intact with their Fritillaries and Coppers fluttering above them.

The butterfly habitat, resplendent with Bistort and Cranesbill

Butterfly list as of 22nd June: 43 species

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Wednesday 19th June 2013

Weekend entomologique Franco-Belge – sans Belges!

Please click on the images to view them larger

This last weekend was billed as a Franco-Belgian weekend, an opportunity for the butterfly/dragonfly enthusiasts of the Nord-Pas de Calais region in France and of Wallonie in Belgium to get together and prospect some potential habitats on the French side of the border, as well as to build a cross-border relationship, which as insects do not respect national boundaries would seem useful from a conservation viewpoint. The French had booked accommodation for up to 32 participants – but in the event not one Belgian turned up.

The Saturday was cool and with little real sunshine. I did manage a brief walk in my favourite northern French forest, where there were by now at least 20 Marsh Fritillaries, Euphydryas aurinia, and perhaps 10 Small Pearl-bordered Fritillaries, Clossiana selene (neither of these being new species for my annual list). One bonus was a single Large Skipper, Ochlodes venatus, which brought my total to 37 species.

Despite the disappointing lack of Belgian participants, the Sunday excursion started in considerably warmer conditions, and the team set out to explore an area in the French Ardennes, adjacent to the Belgian border, and it was lot long before we spotted our first Chequered Skippers, Carterocephalus palaemon, perched on prominent vantage points, surveying their territories in the forest glades. This area also revealed a single Green Hairstreak, Callophrys rubi, and several rather old-looking Speckled Woods, Pararge aegeria.

French butterfly-watchers prospecting the site – not a Belgian to be seen

Having passed through a stretch of woodland, we reached our goal for the morning’s prospecting: a protected area of raised peat bog, entirely surrounded by large trees, and harbouring a rich and highly vulnerable flora, it in turn hosting some relict populations of insects normally associated with more northerly areas, for example in Scandinavia or Boreal Russia. Our chief target in terms of butterflies was the Cranberry Fritillary, Boloria aquilonaris, which had been recorded here in earlier years, but for which no recent records exist. This fast-flying species is entirely restricted to extremely wet peat bogs in which its foodplant, the Cranberry, Vaccinium sp, grows in long strands across the hummocks of sphagnum moss.

The tiny, elegant flowers of Cranberry growing on the Sphagnum moss

Despite numerous false alarms created by sightings of Small Pearl-bordered Fritillaries, no Cranberry Fritillaries were in evidence. This may have been simply due to the extremely late emergence of several butterfly species this year, caused by the exceptionally long cold spell we had right through the spring, or it may be that this tiny relict population has succumbed since the last recorded sightings. Our French guide was despondent about the encroachment of young trees across the site since his last visit, and was disparaging about the Office National des Forets, who own the reserve, and about the Conservatoire d’espaces naturels Champagne-Ardenne, who are supposedly responsible for its maintenance, and yet they still allow this unique and fragile ecosystem to become overgrown.

The wet, peaty areas so rich in specialised wildlife

Although butterflies were in short supply (we did spot two late male Orange-tips, Anthocharis cardamines, and a couple of Brimstones, Gonepteryx rhamni), we were treated to an emergence of several Keeled Skimmer dragonflies, Orthetrum coerulescens, the males of which had not yet had time to develop their bluish-purple “adult” coloration.

A relatively newly-emerged Keeled Skimmer, showing its characteristic wing posture

Shortly afterwards a single, female Northern Emerald, Somatochlora arctica, was caught and identified in the hand before being placed on a conveniently placed post for the photographers in the group. This dragonfly is also a relic of the last ice age, surviving this far south exclusively in these remote peat bogs that are so threatened.

The Northern Emerald next to its picture in the book

The Northern Emerald, recovering from its identification experience

Face shot of the Northern Emerald. The two yellow patches are diagnostic

After lunch we made our way down a beautiful flowery meadow, which might in normal years have been expected to host numerous butterflies, but the only individual of interest was a male Sooty Copper, Lycaena tityrus, again underlining the extraordinarily late flying season we are currently experiencing. We then forded a small stream, crossing into Belgium as we went, and here we searched a wonderful area full of the pale purple, spiky flower-heads of Bistort, Polygonum bistorta. This plant plays host to two highly specialised butterflies, the Violet Copper, Lycaena helle, and the Bog Fritillary, Proclossiana eunomia. Although both occur widely in the Bistort zones further east in Belgium, it was nonetheless worth looking here at least for the Bog Fritillary, as there were rumours of its presence here, but we were unable to locate it on this occasion.

The group prospecting the Bistort field

Our final destination was another peat bog, this time even more difficult to locate and enter, where again the Cranberry Fritillary was our chief target, but despite intensive searching, no butterflies other than a few Small Pearl-bordered Fritillaries and a single passing Large White, Pieris brassicae, which brought my list up to 39 species for the year.

This area is also becoming degraded due to the encroachment of young birch trees, but again there appear to be neither the funds nor the will to take the necessary steps to secure the site’s future, and our guides gloomily predicted that by the time they next visit, the open bog areas will have given way to young birch forest, losing in the process their unique flora and fauna. Being a butterfly enthusiast can be depressing at times. Not only does one only have a “window” of perhaps two or three weekends in which to see them, during which one has to be free to look AND the weather needs to be suitable, but the habitats of some species are so fragile and so fragmented that they can easily be lost forever if the sites are not managed in their favour. This is an expensive, labour-intensive task, and the vast majority of people would not see the value of it anyway.

Birches encroaching onto the site

Luckily I was able to lift us out of any gloomy thoughts we may have had, by stooping to pass underneath an electrified barbed wire fence, and my trousers splitting dramatically from my waist to well down my thighs, revealing all to a highly amused audience!

The dramatic split

My intention on the Monday was to scour the forest areas in the southern part of Belgium for the elusive Poplar Admiral, Limenitis populi, which I had once been treated to once, on my birthday in 2011, but the day dawned cloudy and overcast, followed by torrential downpours, rendering any sighting of this splendid butterfly out of the question (a video of this, one of Europe’s largest butterflies, which I made on that day can be seen in the My Nature Films section on the right of this site). Conditions did improve in the late afternoon, allowing for observation of a steady stream of Red Admirals, Vanessa atalanta, as they powered northwards on their migration from Southern Europe and North Africa.

My final butterfly adventure of the weekend took place in the spur of France known as the Botte de Givet, which projects northwards into Belgium along the Meuse. By now it was late afternoon, and while driving northwards on a fast road, I spotted some largish white butterflies with a characteristic sailing flight by the roadside. Luckily there was a convenient parking spot, so I stopped the car and walked back along the road verge, finding to my delight that they were indeed species number 40, the Black-veined White, Aporia crataegi, feeding avidly on the Red Clover flowers close the road. I was busily photographing these butterflies, which hold a certain mystique for British butterfly-watchers as the species became extinct in the U.K. in the 1920s, and indeed is still retreating in North-west Europe, when suddenly a car drew up behind me, and three gendarmes jumped out and proceeded to demand my papers, which luckily were all in order. They asked me what I was doing, to which I replied “Looking for butterflies”, which they were clearly unconvinced by. Later it turned out that they were interested in why I should be brandishing a camera on a hillside overlooking a large nuclear power station – photographing Black-veined Whites sounded a highly suspicious cover for what I must really be doing: spying on France’s nuclear installations!

Black-veined White, photographed near a nuclear plant in France!

Butterfly list as of 17th June 2013: 40 species

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Tuesday 11th June 2013

A mixed bag

I have just returned to the Netherlands after a long weekend in France and Belgium. High temperatures on Friday augured well for a productive butterfly weekend, and to some degree that wish was to come true, but for some glitches.

After work on Friday, I managed to reach the very southernmost area of the Netherlands, close to Maastricht, where I made my way quickly to an area which I knew was well known for its Glanville Fritillaries, Melitaea cinxia. This is not a species I had observed in the Netherlands previously, and I was anxious to find it before the evening drew in and butterflies disappeared (although Melitaea fritillaries can often be found roosting on flowerheads even at night if one has the dedication to look). Luckily, the sun was still blazing down, and I was soon approaching the beautiful, wildflower-rich slopes of what the Dutch consider a “mountain”, at around 125 metres in height! This area is a mosaic of chalk grassland, and as such is both botanically and entomologically rich.

Although approaching the slopes seemed not to be encouraged, by climbing over gates and crossing a field, I finally found myself in the natural grassland, and almost immediately I spotted my first Glanville Fritillary, soon followed by more than fifteen further individuals. Glanville Fritillaries hold a special interest for British butterfly enthusiasts, as the only place where they occur naturally today is on the broken down cliffs of the south coast of the Isle of Wight, and as such they require quite a major expedition to see them.

The Glanville Fritillary has also an interesting history, being named after Lady Eleanor Glanville, a 17th century butterfly enthusiast who discovered this species in Lincolnshire, where it then also occurred. After her death, one of her sons contested her will on the grounds of lunacy, as eloquently described by Moses Harris in “The Aurelian” in 1766: “This Fly took its Name from the ingenious Lady Glanvil, whose Memory had like to have suffered for her Curiosity. Some Relations that was disappointed by her Will, attempted to let it aside by Acts of Lunacy, for they suggested that none but those who were deprived of their Senses, would go in Pursuit of Butterflies”.

Perhaps I could also have been accused of lunacy, as I stumbled about on the extremely steep and slippery slopes, attempting to secure a respectable photograph!

A Glanville Fritillary poses against the sky

A Dutch mountain, habitat of the Glanville Fritillary

The following day, Saturday 8th June, was also bright and warm. The day’s activity involved a longish walk through a varied mix of deciduous and coniferous woodland and grassland to the south of the Viroinval, one of Belgium’s richest butterfly zones. However, rich or not rich, butterflies were astonishingly conspicuous by their absence, the only new species for my 2013 list being a single female Wall Brown, Lasiommata megera. Other than a few Brimstones, Gonepteryx rhamni, a female Orange-tip, Anthocharis cardamines, perhaps six Speckled Woods, Pararge aegeria, and a gorgeous Scarce Swallowtail, Iphiclides podalirius, nectaring in a garden, there was virtually nothing to report. Why this should be, I do not know. I even wondered whether the entire area might have been sprayed from the air against Oak Processionary Moth larvae, but this seems unlikely.

A Scarce Swallowtail nectaring in a garden

Following a total wash-out on Sunday, my last chance for this weekend came yesterday, Monday 10th June, which started with a brief visit to my favourite large forest in northern France, where despite the cold I soon found a Marsh Fritillary, Euphydryas aurinia, taking the morning sun. This species appears to be restricted in this area to just one large clearing in the centre of this forest complex, and we can only hope that it spreads into some newly felled clearings nearby.

A Marsh Fritillary warming itself in the weak sunshine

Following this initial success, and with the temperature rising slightly, it was not long before I spotted the first of perhaps fifteen Small Pearl-bordered Fritillaries, Clossiana selene, some of which appeared to be newly emerged individuals.

A newly-emerged Small Pearl-bordered Fritillary, its wings not yet quite in place

From here I headed eastwards, back to the Viroinval, but this time to the north side, with its sun-warmed south-facing chalky slopes. Here I added a further species to my list, the Large Wall, Lasiommata maera, which shot past as I was admiring its rocky habitat, not stopping to allow me to obtain a shot. What did cooperate much more kindly was another new species, the Small Blue, Cupido minimus, which posed beautifully while laying its eggs in the flowerheads of its larval foodplant, the Kidney Vetch.

A Small Blue laying on its foodplant, Kidney Vetch

Other species here included a further Scarce Swallowtail, Iphiclides podalirius, Brown Argus, Aricia agestis, Green Hairstreak, Callophrys rubi, Dingy Skipper, Erynnis tages, and Red-underwing Skipper, Spialia sertorius.

As I still had a marathon drive ahead of me, I then set off back towards the Netherlands, stopping again near Maastricht, but this time on the other side of the city, close to the Sint-Pietersberg, another Dutch “mountain”. Here I was hoping to find the Mazarine Blue, Cyaniris semiargus, and it was not long before I had seen my first, fluttering through the wonderful flowery meadow of a newly-created reserve only just outside the city. The butterflies were already looking worn, so it was lucky that I visited when I did, as they will doubtless soon be over.

A Mazarine Blue poses on its foodplant, Red Clover

Like the Glanville Fritillary, the Mazarine Blue is also an almost mythical species for British butterfly-watchers, as despite being relatively widespread in southern England in the nineteenth century, it is now totally extinct in the U.K. Here, however, it appears to be thriving, and it is nice to know that people are working for its success, creating reserves and leaving the clover-filled grasslands uncut for the benefit of this attractive species.

Habitat of the Mazarine Blue

Butterfly list as of 11th June: 36 species