Butterfly Islands: On Mottistone Down.

Wednesday 7 August 2019

On Mottistone Down.

Today's visit to Mottistone Down in search of downland butterflies was somewhat marred by a very brisk wind.Still,the sun was shining and at this time of the year temperatures are pleasant.Luckily there are sunny sheltered spots where butterflies seem to congregate and a good number of Chalk-hill Blue,Common Blue,Brown Argus,Gatekeeper,Meadow Brown,and Wall Brown were seen.Inevitably several Painted Lady were also in evidence. However, in order to see one particular butterfly species I had to search the part of the Down known as the Common. This is the exposed open area of the Down consisiting of bracken and heather.Here the Grayling prefers to stay and is normally found on any bare patches of ground of chalk or old heather.

Mottistone Down looks out over the Isle of Wights' south-west coast.The Down is a Site of Scientific Interest covering 78 acres and most of the area is owned by the National Trust.It is biologically important due to its chalk and neutral grasslands.

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The Adonis Blue

The Large Tortoiseshell

It seems the general view on the status of the Large Tortoiseshell in Britain is that it is now extinct as a breeding butterfly.
It is a butterfly of woodland edges and hedgerows that abound in willows,elms,and poplars.These trees are used by the adult to lay its eggs and this single brood appears in July and August.The emerging butterfly then hibernates over the winter in log piles and hollow trees until the next spring.
On the Isle of Wight sightings are more often than not made from early March to April.Have these butterflies overwintered on the Island or have they come from the continent where it is common?
Any sightings made in July/August pose the same question.Another explanation could be that captive-bred releases are responsible.Only the discovery of eggs and caterpillars will probably answer these questions.

I can now report that evidence has been found of breeding just along the coast at Portland in Dorset (June 2020) and again at the same location in the summer of 2021.

The Glanville Fritillary

This elegant butterfly is mainly confined to the crumbling undercliffs and chalk downs of the Isle of Wight.It is also found on the Channel Islands and at one or two isolated colonies on the British mainland.In Britain the Glanville Fritillary is at the extreme north-western edge of its range.On the continent it is readily found in flowery habitats.
Around the southern shores of the Isle of Wight the cliffs constantly erode causing them to slip away and provide perfect conditions for new growths of the butterflies laval host plant,Ribwort Plantain.
The eggs are laid to the underside of the leaves of this plant and normally hatch after about three weeks.The resulting caterpillars live together in communal webs spun over the plantain.In the autumn they hibernate and recommence feeding in the spring,eventually dispersing to prepare for pupation.
The adult butterfly is on the wing from May to the end of June with the female being larger than the male.They will feed on,amongst other things, Birds-foot Trefoil and Thrift.

The Wall Brown

On the Isle of Wight in particular,the Wall Brown is a butterfly of field edges,coastal cliffs and dunes,and rabbit-grazed downland.
The male is territorial and spends much of the time patrolling and basking on the ground.
The female,which lacks the males conspicuous dark sex brand across the forewings,is larger.The undersides of both sexes are beautifully cryptic when at rest.
The Wall Brown generally produces two broods a year,the first from late April until late June and the second from mid-July to mid-September.

Wednesday 7 August 2019

On Mottistone Down.

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