The Portland Silver-studded Blue.
Posted: Mon Jun 30, 2014 5:33 pm
I spent last weekend exploring the quarries of Portland for the Silver-studded Blue - Plebejus argus. Listed below are the sites I visited and the number of butterflies that I encountered. On the Saturday, I arrived at 12 am, it was sunny but in the afternoon cloudy with some rain and windy. In the late afternoon it was full sunshine. On the Sunday it was warm with sunny spells. I must admit that I had trouble finding many pristine examples to photograph.
Tout Quarry - 8. 5 males - 3 females.
Kings Barrow Quarry - 1 male.
Broadcroft Quarry - 9. 6 males -3 females.
Nicodemus knob. Coastal site to the east of King's Barrow Quarry - 0 . My visit here on the Friday coincided with windy weather and perhaps I was too early on the Saturday, the bank below the rock feature was in shadow. On the 25th June 10 were recorded here - Dorset butterfly sightings.
On the Saturday in Tout Quarry, I made the aquaintance of Ken a local naturalist and entomologist from Easton. Ken like others, considers the Portland Silver-studded Blue as subspecies cretaceus. A equal number of other lepidopterists state that cretaceus is infact extinct.
I have seen historical cretaceus specimens from quite a few of its localities on its former range of the North and South Downs. The females of cretaceus were a bit of a mixture, some with various amount of blue scaling on the wings, often confined to the inner areas of the forewings . The red sub marginal spots were often much brighter in the females on the chalk downs. Also there is the historic specimen from Dover on the species page showing the brown female. Historical specimens are a very valuable resource for study and I have included a few of the rarely seen extinct chalkland race of cretaceus.
The eastern most locality for cretaceus was the chalk downland near Bishops Waltham in Hampshire and females from this locality were very pretty with various amounts of blue scaling. The extinct chalk downland cretaceus race was thus seperated from the Silver-studded Blue on Portland by a considerable distance and the extensive lowland heathland populations of Plebejus argus.
On Portland the limestone race is quite a scarce butterfly with very small populations quite unlike the extensive colonies of the other limestone race caernensis on the Great Orme. It seems to me that the Silver-studded blues on Portland may be a relic population cut off from the extensive heathland colonies in Dorset. It really does not seem suited to its quarry habitat, which as Broadcroft quarry shows, rapidly becomes overgrown with scrub, with the butterfly there mainly occurring in the conservation scraped areas to the east of the quarry road. un - helmeted local youths on their mini motor bikes seem to like this area and spoil what would be a lovely site.
In Tout Quarry, the Silver-studded blues I found were along one short sheltered enclosed section of the sculpture park and the males liked one particular area of low privet-bramble to bask on where on two occasions they were joined by females.
Other notable butterflies seen were Lulworth Skipper. 2 at Broadcroft quarry.
Chalkhill Blue 1 male - very early for this butterfly. Tout Quarry.
Grayling. 2 at Tout Quarry. Photo.
Dingy Skipper 1 at Tout Quarry. Very late for this butterfly. photo.
May I remind members that if they find any blue females of Silver-studded blues among the lowland heath populations of southern England to show them here. Preen Heath in Shropshire has some and so has the dune population in Cornwall.
Peter.
Tout Quarry. Broadcroft Quarry. Historical specimens of subspecies of cretaceus. Tout Quarry.
Tout Quarry - 8. 5 males - 3 females.
Kings Barrow Quarry - 1 male.
Broadcroft Quarry - 9. 6 males -3 females.
Nicodemus knob. Coastal site to the east of King's Barrow Quarry - 0 . My visit here on the Friday coincided with windy weather and perhaps I was too early on the Saturday, the bank below the rock feature was in shadow. On the 25th June 10 were recorded here - Dorset butterfly sightings.
On the Saturday in Tout Quarry, I made the aquaintance of Ken a local naturalist and entomologist from Easton. Ken like others, considers the Portland Silver-studded Blue as subspecies cretaceus. A equal number of other lepidopterists state that cretaceus is infact extinct.
I have seen historical cretaceus specimens from quite a few of its localities on its former range of the North and South Downs. The females of cretaceus were a bit of a mixture, some with various amount of blue scaling on the wings, often confined to the inner areas of the forewings . The red sub marginal spots were often much brighter in the females on the chalk downs. Also there is the historic specimen from Dover on the species page showing the brown female. Historical specimens are a very valuable resource for study and I have included a few of the rarely seen extinct chalkland race of cretaceus.
The eastern most locality for cretaceus was the chalk downland near Bishops Waltham in Hampshire and females from this locality were very pretty with various amounts of blue scaling. The extinct chalk downland cretaceus race was thus seperated from the Silver-studded Blue on Portland by a considerable distance and the extensive lowland heathland populations of Plebejus argus.
On Portland the limestone race is quite a scarce butterfly with very small populations quite unlike the extensive colonies of the other limestone race caernensis on the Great Orme. It seems to me that the Silver-studded blues on Portland may be a relic population cut off from the extensive heathland colonies in Dorset. It really does not seem suited to its quarry habitat, which as Broadcroft quarry shows, rapidly becomes overgrown with scrub, with the butterfly there mainly occurring in the conservation scraped areas to the east of the quarry road. un - helmeted local youths on their mini motor bikes seem to like this area and spoil what would be a lovely site.
In Tout Quarry, the Silver-studded blues I found were along one short sheltered enclosed section of the sculpture park and the males liked one particular area of low privet-bramble to bask on where on two occasions they were joined by females.
Other notable butterflies seen were Lulworth Skipper. 2 at Broadcroft quarry.
Chalkhill Blue 1 male - very early for this butterfly. Tout Quarry.
Grayling. 2 at Tout Quarry. Photo.
Dingy Skipper 1 at Tout Quarry. Very late for this butterfly. photo.
May I remind members that if they find any blue females of Silver-studded blues among the lowland heath populations of southern England to show them here. Preen Heath in Shropshire has some and so has the dune population in Cornwall.
Peter.
Tout Quarry. Broadcroft Quarry. Historical specimens of subspecies of cretaceus. Tout Quarry.