The extinct British Plebejus argus masseyi & cretaceus ssp.

Very nice, I like the caernensis race. Again the females have the extensive blue scaling, but are much smaller than the extinct masseyi. I have seen them on the limestone of the Great Ormes head. This wonderful area is high on my list of places to visit.

Dunc

The semele from Great Orme is ssp. thyone, which is renowned for its diminutive size.

I spent a single day there in 1981. It was heavily overcast but dry and not too cold. The caernensis were roosting on every available bit of vegetation and could easily be picked up with the fingers or boxed - just as well because there were people everywhere so I wouldn't have wanted to get a net out. They were incredibly abundant, I could easily have had hundreds if I'd wanted. I only saw a couple of thyone; probably a lot to do with the weather but I'd imagine they're nowhere near as abundant as caernensis.

Bob

these are the semele

The extinct British subspecies Plebejus argus cretaceus

In the U.K, we have a few endemic butterfly subspecies that occur nowhere else . Among the butterflies that are found here are a number of interesting geographical races of the Silver-studded Blue, Plebejus argus. On the chalk hills of England there was until quite recently a subspecies of Plebejus argus that James Tutt in 1909 named cretaceus because it was only to be found on the chalk Downs of Kent, Surrey, Sussex? and Hampshire. There are still a number of lepidopterists and conservationists that maintain subspecies cretaceus is not in fact extinct and those populations which occur on the limestone of Portland in Dorset should be referable to that taxon. Other maintain that those plebejus argus populations on Portland may resemble the extinct cretaceus, but are not that subspecies. Those specimens that I have seen from the quarries of Portland do in fact seem close to some of the lost downland populations of cretaceus. Whatever the truth, those limestone populations on Portland have been shown to be distinct from the usual plebejus argus colonies that frequent the acid heathlands of southern England. The heaths of Dorset with those of the nearby New Forest in Hampshire contain some of the largest remaining colonies of Plebejus argus in the U.K.

The males of the subspecies cretaceus were larger and a more intense brighter blue than than our remaining P. argus populations, with the exception of those occurring on Portland. The undersides are less heavily spotted and are more of a paler bluish-grey. Tutt said in his original description that the hindwing black margin spots were more distinct in cretaceus and were not in a continuous band as in the populations occurring on the heathlands. He also mentioned that the black forewing margin band of cretaceus was thinner. While the narrow forewing band and distinct spotted margins do appear in many specimens of cretaceus, these morphological differences do vary both in the extinct cretaceus race and those still to be found on our southern heathlands.
I have seen specimens of cretaceus from the following localities on the chalk, some of which were well known for there populations of the now extinct? butterfly.
Kent : Biggin's Hill, Halling, Herne Bay, Eynesford, Swanscombe, Snodland, Badger's Mount, Folkestone and Dover.
Surrey, Wooton near Guildford.
Hampshire and Sussex. The South Downs . Bishops Waltham [ Hants].

It seems that cretaceus of the North and South Downs finally became extinct in the mid 1970's. An enormous amount of fine downland was ploughed during and after the Second War War. The widespread introduction of that horror myxomstosis would have seen a great reduction in the habitat required by this unique subspecies and a reduction and changes in livestock grazing further hastened its extinction. As the downland habitat changed, the taller grasses and scrub shaded out the low-growing legumes, the foodplants of this and the other chalk downland blues. Michael Chalmers-Hunt 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. 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 . 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 mentioned subspecies cretaceus in its Downland habitat in Kent, just before it became extinct there. In 1950, J.E. Owen of Lewisham, 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.


Males of cretaceus from Kent


Males and females of cretaceus from Kent.


Verso's of both sexes of cretaceus from Kent


Males of the limestone Portland race.


Specimens from the Purbeck hills in Dorset. Plebejus argus argus?


Specimens of cretaceus from Eynesford Kent. See the old field reports mentioned above.

I believe this is the first time a detailed series of specimens from the different localities of the extinct taxon have been shown anywhere and I would like to thank Mr Clive Pratt for his time, help and his permission to have his very fine collection photographed for their study. More specimens to follow.

According to the old Butterflies of Croydon book there was a colony of cretaceus about 2 miles from where I lived growing up. Once I found this out I searched for it, which took quite a while but I'm fairly sure I eventually found the site (these things were much harder before the days of GPS). I reckon I must have missed it by about two years!

Bob

If you want to view this beautiful butterfly on Portland you had better be quick, since butterfly conservation started "managing" it's habitat it has decreased markedly, by managing I mean banning all collecting and let the whole place become overgrown with brambles, such a shame.