A Review of Lepidoptera in Britain for 1973

A REVIEW OF LEPIDOPTERA IN BRITAIN FOR 1973 BARON DE W O R M S

THE year under review was ushered in with yet another very mild spell and for the third year in succession virtually no hard weather persisted for the recognised winter over almost the whole of southern England. As in 1972 a very warm and sunny period prevailed during the second half of March with the sallows in füll bloom by the middle of that month. All the early species of moths were well out by their normal date of appearance and some of them even on the early side. Once more hibernated specimens of the Dotted Chestnut (Dasycampa rubiginea Schiff.) were numerous on the Bagshot Sand. April was a very mixed month in the south, with some very fine days during the first half which brought out the over-wintering butterflies including the Large Tortoiseshell (Nymphalis polychloros Linn.) of which several were seen together in a Surrey locality over the Easter holiday during the third week of April. It is heartening to know that this fine insect may be making a comeback after many years of almost Virtual absence and it is hoped that this butterfly will soon again be inhabiting the Eastern Counties and notably Suffolk, once its most prolific region. The Brimstone (Gonepteryx rhamni Linn.) was abundant in most areas during the early spring.

May was a further most congenial month with high temperatures during the middle period. The Pearl-bordered Fritillary (Clossiana euphrosyne Linn.) was well on the wing by the middle week— together with the Orange-tip (Anthocharis cardamines Linn.). It was during the last week of this month that the first of a remarkable sequence of migrant species appeared. This was the capture on the southern outskirts of London of a Spurge Hawkmoth (Celerio euphorbiae Linn.), possibly the rarest of the Sphingidae in this country, though very widespread on the Continent. June was indeed a contrast to that of the previous year. The sun shone almost continuously throughout the month which was indeed to prove to be the prelude to one of the finest and wärmest summers of the Century with a veritable profusion of the lepidoptera in most parts of the British Isles. The shade temperature in June often exceeded 80°F. In the south-western region during the last week many butterflies were out well before their usual date such as the Silver-washed Fritillary (Argynnis paphia Linn.) together with the High Brown Fritillary (Argynnis cydippe Linn.), while the local form of the Heath Fritillary (Mellicta athalia Rott.) was quite plentiful at that period in its special haunts in Devon. The glorious weather continued without a break tili the middle of July.

During the last days of June a Bedstraw Hawk (Hyles galii Rott.) was taken on the north coast of Norfolk and it may well have been the offspring of a fair invasion of that fine moth in

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1972. However, it turned out to be the forerunner of what would seem to have been a huge Immigration of this species, mainly during the latter half of July, since over fifty specimens were reported from all parts of the country with many records even in Scotland and as far as the Orkneys. It was possibly the largest number of these moths noted this Century in one year, while in September larvae of the Bedstraw Hawk were taken in numbers on coasts, chiefly of Cumberland and Lincolnshire, feeding off Galium. But those found wild inland, including some in the centre of Edinburgh, had the fireweed (Epilobium) as their chief foodplant. But there were no reports of the larvae from Suffolk in 1973. The origin of these invaders may have been Holland where this Hawkmoth has recently become quite a common breeding species and let us hope a similar phenomenon may follow suit in the British Isles.

The early part of July brought out a big emergence of lepidoptera and moths in plenty with the thermometer in the 70s almost each day. Among the butterflies which flourished at this time was the Purple Emperor (Apatura iris Linn.). On a particularly warm day about the middle of July one keen observer saw as many as a dozen of this grand insect congregated round a water butt in a locality in the south of England. The end of July brought the record of Camberwell Beauties (Nymphalis antiopa Linn.) in the south-east and one even in central London. Further Large Tortoiseshells (N. polychloros Linn.) were seen north of London on the border of the Midlands. In Cornwall about this date there was a spate of the Large Footman (Lithosia quadra Linn.), probably mostly immigrants as were a few of the Great Brocade (Eurois occulta Linn.) in the eastern areas.

During the first days of August many marsh species were especially plentiful in East Suffolk, in particular the Whitemantled Wainscot (Nonagria neurica H체bn.) and Fenn's Wainscot (Arenostola brevilinea Fenn.). This period also saw a great emergence of the Chalkhill Blue (Lysandra coridon Poda) which appeared in thousands, especially on some of the Surrey downs accompanied in some localities by the Pearl Skippers (Hesperia comma Linn.). Together with the Bedstraw Hawks, already referred to, several other species of migrant moths were observed at this part of early August, including the little noctuid, the Purple Marbled (Eublemma ostri?ia H체bn.) and Blair's Mocha (Cosymbia puppillaria H체bn.) of which two specimens were taken in the New Forest. The middle of August saw the shade temperature in a large part of England soar to 90째F which brought on quite a phenomenal burst of butterflies, in particular the Small Tortoiseshell (Aglais urticae Linn.) which has seldom been seen in such profusion. The emergence reached its climax in early September which saw the Red Admiral (Nymphalis atalanta Linn.) in great plenty in the southern counties, but only a few sporadic Painted

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Ladies (Pyrameis cardui Linn.). However, the Clouded Yellow (Cottas croceus Pourc.) reappeared in some numbers, chiefly in the south-western areas, after several years of great paucity. Düring the first week of September there seems to have been another great invasion of migrants, also largely in the western regions.

Huge numbers of the Silver-Y (Plusia gamma Linn.) came to lighttraps in many parts of the country, often accompanied by the Convolvulus Hawk (Herse convolvuli Linn.) and the little Vestal (Rhodometra sacraria Linn.) which was seen in many parts of southern England. The great Death's Head Hawk (Acherontia atropos Linn.), also made up this galaxy with a good many records in over a large part of England. Several rarities were recorded as well, a Long-tailed Blue (Lampides baeticus Linn.) was taken in Warwickshire and the third British example of the Paignton Snout (Hypena obesalis Treits.) was captured also in the Midlands.

Düring the early autumn too there were noted several Scarce Bordered Straws (Heliothis armigera Hübn.) also the Delicate (Leucania vitellina Hübn.) and the White-speck (L. unipuncta Haworth), chiefly in the south-west. The Northern Dart (Amathes alpicola Zett.) was once more seen in the Connemara region of western Ireland.

In late September that fine newly-discovered moth the Large Frosted Orange (Gortyna borelii Boisd.) was seen again in its restricted haunts on the east coast. The autumn in early October saw further migrations with the appearance of the Pyrales, the Yellow-underwing Pearl (Uresiphita polygonalis Schiff.) and the Scarce Olive-tree Pearl (Palpita unionalis Hübn.) on the south coast of England. Düring the late summer that large noctuid the Stout Dart (Spaelotis ravida Schiff.) was prevalent in the eastern and south-eastern regions of England and probably a good proportion were of migrant origin. But the most spectacular visitor at this time of the year, especially in late September, was the great Monarch Butterfly (Danaus plexippus Linn.) of which at least seven were sighted in Devon and Cornwall. There was a spate of this great migrant in North America whence some may have crossed the Atlantic to find a haven on our shores as they did under similar conditions in 1968.

In the autumn too Blair's Pinion (Lithophane leautieri Boisd.) first recorded in the Isle of Wight in 1951, found its way to the London district in 1973, while the Black-streaked Pug (Eupithecia phoeniciata Ramb.) first noted near Penzance in 1959, has spread to the Isle of Wight where it was numerous in September. Both insects feed on macrocarpa in the larval S t a t e .

T h e Red Admirals and Small Tortoiseshells were still on the wing in November, but a notable absentee was the Comma (Polygonia c-album Linn.). About the middle of this month the

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Plumed Prominent (Ptilophora plumigera Schiff.) was in remarkable numbers, especially on the Surrey downs, as was also the December Moth (Poecilocampa populi Linn.).

DĂźring 1972, at least two important records came to light. In the last days of July that year a small noctuid moth was taken at a mercury-vapour trap in some wild hilly country in South Wales and it proved to be what has been called the Silurian (Eriopygodes imbecilla Fab.), a native of alpine Europe and new to the British Isles, but so far no other examples have been reported from that region which may well harbour this rather obscure little moth.

But even more remarkable was the discovery of a specimen of Eversman's Rustic (Actebia fennica Linn.), also obtained in a trap at Shepperton, Middlesex, in August, 1972. This is only the second record of this circumpolar species emanating possibly from Scandinavia. The only previous example was taken as far back as 1850 in a wood near Chesterfield and is still in the York Museum.

To sum up, the year 1973 was in great contrast to its two predecessors. The wonderfully fine summer brought forth a veritable abundance of butterflies together with a great immigration of certain moths, of which that of the Bedstraw Hawk was by far the most outstanding, making 1973 a most memorable and prolific season.

Baron de Worms, M.A., Ph.D., F.L.S., F.R.E.S., M.B.O.U., Three Oaks, Shore's Road, Horsell, Woking, Surrey.