Thursday 4 June 2015

A very rare Fritillary indeed 30th May 2015

Seizing a window of opportunity where sun was actually forecast for a whole day in this benighted spring of bad weather, Peter and myself headed for the unusual location of Croydon to try and seek out some Glanville Fritillaries.

Glanville Fritillaries are the rarest of the fritillary butterfly species frequenting Great Britain and their stronghold is now limited to a small area on the south coast of the Isle of Wight although in much earlier times they were to be found in scattered colonies as far north as Lincolnshire. No one knows quite why they are so scarce, as in Europe they extend to latitudes equivalent to that of Shetland. One theory is that their larval foodplant, Ribwort Plantain, requires broken ground to colonise and additional control of other slower growing plants which, if not checked will smother it and not allow it to survive. Under current general conditions in Great Britain it is thought the foodplant is unable to survive in sufficient quantities to support the caterpillars, apart that is from the colony on The Isle of Wight where regular natural cliff falls create the broken ground that the plantain requires.

Glanville Fritillaries are named after Lady Eleanor Glanville who has the distinction of discovering them in Lincolnshire around 1690. She herself was an interesting character and, reflecting the less enlightened times in which she lived and died, her will was disputed by one of her sons on the grounds that her great interest in butterflies indicated that she was not quite right in her mind! The fritillary she discovered was originally called The Lincolnshire Fritillary and then the name Dullidge Fritillary was favoured after the discovery of a population near Dulwich. Further dissension arose when it was suggested to call it Plantain Fritillary before the name Glanville was proposed. These two latter names each had their strong proponents but  Glanville finally won out in the 19th century and the name has remained as such ever since

There have been at least a couple of re-introduction schemes tried in the relatively recent past, one at Wrecclesham in Surrey and another near Croydon, also in Surrey. The Wrecclesham colony died out as the habitat which was a disused quarry became a landfill site and the remnants of that population were rumoured to have been transferred by persons unknown to Hutchinson's Bank near Croydon  in 2011 where they currently thrive in small numbers, protected in a carefully managed dry chalkland  habitat on the outskirts of Croydon by The London Wildlife Trust. 

Setting off from Oxford the sun was strong and unhindered by any cloud but progressively as we headed southwards the clouds increased until by the time we reached the reserve in mid morning we were restricted to just the occasional sunny interval. It was also unseasonably cold and as we parked the car it was far from promising for searching for butterflies .

Walking up the main track to the reserve we passed through a gate and encountered some ten or so butterfly enthusiasts from various parts of England standing about in what we were informed was the most likely place to see a Glanville Fritillary. Two or three fritillaries had been seen earlier in the morning when it was sunnier but now there was little indication that we would be lucky enough to see one. The general lack of sun was an obvious reason for the acute shortage of any butterflies with only a Small Blue, a very frayed Dingy Skipper and a couple of Small Heaths braving the conditions.

Hutchinson Bank Reserve
For around forty five futile minutes we stared at various parts of the reserve until a local enthusiast who seemed to be an unofficial warden suggested he take us to where a 'Glanville' had been seen earlier in the morning, which entailed walking a short distance further into the reserve and down into a sheltered shallow valley. Most of us went with him whilst others elected to remain in the 'favoured' spot.

We arrived at the sheltered valley and met another fritillary enthusiast who pointed to the ground. There by the track was a female Glanville Fritillary, settled low on the ground, sheltered from the cold breeze in an area of Ribwort Plantain and Bird's Foot Trefoil, wings spread wide open to absorb the weak rays of whatever sun periodically radiated through the clouds. It was as easy as that. 

I suppose we were fortunate, as in strong sunlight and warmer conditions the fritillaries would be much more active and flying about but now starved of the sun's sustenance this individual was sluggish, almost comatose and allowed us, in turn, to take her picture from as close as we fancied. It was all very civilised, the butterfly totally co-operative and all of us in a very English way quietly queuing to take her photo but not until the previous photographer had completed their turn.

Peter's turn to photo the fritillary

Female Glanville Fritillary
The fritillary remained firmly on its selected plant for quite some time and then moved in a fluttering flight, low across the ground to the other side of the track and settled once more on a blade of grass, turning its body to the diffuse sun in an effort to absorb any warmth she could. So static was the butterfly that we all eventually had enough and left her, still perched on the blade of grass. A chequered bright ginger splash amongst  the various greens of the grasses.

A subsequent short walk around the lower part of the reserve yielded a Common Blue, a Small Heath and another co-operative Small Blue as well as a Common Lizard sunning itself on a small log, but that was all. 

Small Blue
I wandered back for one last look at the fritillary, only to find it had gone. We never saw another one although up to thirty nine had been reported a week ago in sunnier conditions. I wandered around the small area recently frequented by the fritillary but although there was plenty of its foodplant in evidence, of the butterfly there was no sign. Obviously it had garnered enough warmth to energise it to move further away. My search however did reveal a Roman Snail, hunkered down and looking huge, almost exotic, amongst the Ribwort Plantain and Bird's Foot Trefoil. 

Ribwort Plantain - foodplant for Glanville Fritillary larvae
Bird's Foot Trefoil - foodplant for the Glanville Fritillary butterfly
Noticeably larger than our common Garden Snail, Roman Snails are known as Escargot in France or Edible Snails and are much prized as a gastronomic delicacy in that country. Here in Great Britain they are protected and scarce, being restricted to unimproved grassy and bushy wasteland in southern England. They are mature between two to five years and can live for up to twenty years and move only a few metres in their lifetime.

Roman Snail or Escargot