Post by nomad on Oct 25, 2015 9:36:26 GMT
The extinct British subspecies Plebejus argus cretaceus.
Up to the 1970's there was an interesting race of Plebejus argus named cretaceus Tutt on the chalk hills of Southeast England. The extinction of cretaceus in Britain came about when there was a massive deline in Britain's Lycaenidae mainly through habitat change because of changes in farming practices and the eradication of the rabbit population through the introduction of myxomatosis.
Whether or not cretaceus is a good subspecies has been debated by a number of different authors. Here is Tutt's 1909 original description
Male. Bright blue, dark margin of forewings narrow or absent (sometimes quite pallid), discoidal lunules obsolete, on hindwings; interneural marginal spots replace usual band; underside bluish-grey, spots clearly defined.
Female. Dark fuscous, often tinged with blue, orange marginal lunules on hindwings poorly developed, on forewings usually obsolete; underside pale brownish, with well-defined spots, and whitish submarginal border.
It has also been highly debated as to whether or not the P. argus race occurring on the limestone headland of the Isle of Portland in Dorset Southern England is in fact referable to ssp cretaceus . The Portland population there does seem more akin to those found elsewhere in Dorset on the lowland Heaths. Today the population of P. argus on Portland, where it was once common, has declined to an alarming extent and this population is now endangered and should not be collected. Most of the high limestone plateau of that island has been quarried for the famous Portland limestone and the butterflies habitat has been destroyed. P. argus was forced to take refuge in the abandoned quarries of Portland and as they become overgrown the butterfly declines.
Ssp cretaceus was most widespread in Kent where it was recorded from a numbers of localities in Kent : Biggin's Hill, Halling, Herne Bay, Eynesford, Swanscombe, Snodland, Badger's Mount, Folkestone and Dover. I have not seen specimens from Sussex but it no doubt occured there. There was a nice population of ssp cretaceus with especially blue females on the downs above Bishops Waltham in East Hampshire.
Michael Chalmers-Hunt a well known collector and author who wrote the Butterflies and Moths of Kent [1979] entirely blamed the lost of what he called the finest of the P. argus races in Britain, cretaceus on myxomatosis. He records that when this disease was introduced to the rabbit population in the 1950's, the Kentish colonies soon disappeared. Unlike the extinct subspecies masseyi, most books seem silent on the passing of cretaceus, so any first hand field knowledge of the species should be recorded.
I have found a couple of brief articles in The Entomological Record and Journal of Variation that mentions subspecies cretaceus in its Downland habitat in Kent, just before it became extinct In this locality . In 1950, J.E. Owen of Lewisham ( I was born in that area of London, six years later), wrote of the butterflies to be found in the chalk Darent Valley between Eynesford and Shoreham. He mentioned that here cretaceus was very local and confined to a couple of fields and the best time to find it on the wing was in late June. Michael-Chalmers-Hunt also observed cretaceus near Shoreham at the end of June around the same period and found it in the clearings between the hawthorn scrub where it was flying with Polyommatus icarus, Maniola jurtina, Ochlodes sylvantus and the Burnet moths Zygaena lonicerae and Zygaena filpendulae.
It is possible that some of the collectors alive today would have collected or observed cretaceus in the wild. It would be invaluable to have some first hand account of this beautiful blue butterfly in its downland habitat, so if you were lucky to have seen it in the field, please do tell of your experiences . They should be recorded for prosperity.
Specimens of P. argus cretaceus.
Three P. argus subspecies from Britain. Notice compared to the lowland heathland P. argus argus, the less distinct marginal band on the male recto of cretaceus and the much paler almost lilac verso underside, which was a constant feature of the lost chalk downland race.
A fine plate of British Lycaenidae by A.D.A. Russwurm showing four Plebejus argus subspecies with a few aberrations. Plate from South's British Butterflies by T.G. Howarth 1973.
Up to the 1970's there was an interesting race of Plebejus argus named cretaceus Tutt on the chalk hills of Southeast England. The extinction of cretaceus in Britain came about when there was a massive deline in Britain's Lycaenidae mainly through habitat change because of changes in farming practices and the eradication of the rabbit population through the introduction of myxomatosis.
Whether or not cretaceus is a good subspecies has been debated by a number of different authors. Here is Tutt's 1909 original description
Male. Bright blue, dark margin of forewings narrow or absent (sometimes quite pallid), discoidal lunules obsolete, on hindwings; interneural marginal spots replace usual band; underside bluish-grey, spots clearly defined.
Female. Dark fuscous, often tinged with blue, orange marginal lunules on hindwings poorly developed, on forewings usually obsolete; underside pale brownish, with well-defined spots, and whitish submarginal border.
It has also been highly debated as to whether or not the P. argus race occurring on the limestone headland of the Isle of Portland in Dorset Southern England is in fact referable to ssp cretaceus . The Portland population there does seem more akin to those found elsewhere in Dorset on the lowland Heaths. Today the population of P. argus on Portland, where it was once common, has declined to an alarming extent and this population is now endangered and should not be collected. Most of the high limestone plateau of that island has been quarried for the famous Portland limestone and the butterflies habitat has been destroyed. P. argus was forced to take refuge in the abandoned quarries of Portland and as they become overgrown the butterfly declines.
Ssp cretaceus was most widespread in Kent where it was recorded from a numbers of localities in Kent : Biggin's Hill, Halling, Herne Bay, Eynesford, Swanscombe, Snodland, Badger's Mount, Folkestone and Dover. I have not seen specimens from Sussex but it no doubt occured there. There was a nice population of ssp cretaceus with especially blue females on the downs above Bishops Waltham in East Hampshire.
Michael Chalmers-Hunt a well known collector and author who wrote the Butterflies and Moths of Kent [1979] entirely blamed the lost of what he called the finest of the P. argus races in Britain, cretaceus on myxomatosis. He records that when this disease was introduced to the rabbit population in the 1950's, the Kentish colonies soon disappeared. Unlike the extinct subspecies masseyi, most books seem silent on the passing of cretaceus, so any first hand field knowledge of the species should be recorded.
I have found a couple of brief articles in The Entomological Record and Journal of Variation that mentions subspecies cretaceus in its Downland habitat in Kent, just before it became extinct In this locality . In 1950, J.E. Owen of Lewisham ( I was born in that area of London, six years later), wrote of the butterflies to be found in the chalk Darent Valley between Eynesford and Shoreham. He mentioned that here cretaceus was very local and confined to a couple of fields and the best time to find it on the wing was in late June. Michael-Chalmers-Hunt also observed cretaceus near Shoreham at the end of June around the same period and found it in the clearings between the hawthorn scrub where it was flying with Polyommatus icarus, Maniola jurtina, Ochlodes sylvantus and the Burnet moths Zygaena lonicerae and Zygaena filpendulae.
It is possible that some of the collectors alive today would have collected or observed cretaceus in the wild. It would be invaluable to have some first hand account of this beautiful blue butterfly in its downland habitat, so if you were lucky to have seen it in the field, please do tell of your experiences . They should be recorded for prosperity.
Specimens of P. argus cretaceus.
Three P. argus subspecies from Britain. Notice compared to the lowland heathland P. argus argus, the less distinct marginal band on the male recto of cretaceus and the much paler almost lilac verso underside, which was a constant feature of the lost chalk downland race.
A fine plate of British Lycaenidae by A.D.A. Russwurm showing four Plebejus argus subspecies with a few aberrations. Plate from South's British Butterflies by T.G. Howarth 1973.
