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The butterflies of Wicken Fen
Guides to Wicken Fen Number 15

Adrian Colston and Ralph Sargeant

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This annotated checklist supersedes the one by John Smart in 1972 and that produced in 1985 by Tim Bennett.

Small skipper (Thymelicus sylvestris) This butterfly is not common on the ancient fen as the habitat is probably too wet. However, it is regularly recorded on Little Breed Fen, particularly in compartment 23.

Essex skipper (Thymelicus lineola) Essex skipper is more common than the small skipper and can be found throughout the Fen. It is most abundant during August. It can be distinguished from the small skipper by the black undersides of the antennae tips.

Large skipper (Ochlodes venata) This is a common species which Bennett (1985) considered to be on the increase. During the 1990s it was recorded throughout the Fen.

Grizzled skipper (Pyrgus malvae) Two individuals were recorded in 1940 (David Wilson pers comm) but none have been recorded since. Grizzled skippers are now very localised in Cambridgeshire (Bennett and Perrin 1994).

Swallowtail (Papilio machaon britannicus) In the 1950s, probably 1952, the swallowtail became extinct at Wicken Fen. Although the exact reason for the loss is not known, it is likely that it occurred because the amount of suitable open fen habitat had declined from 120ha to less than 8ha. This was as a result of scrub invasion over the previous 50 years and also because the entire site became drier as the water table dropped due to adjacent agricultural drainage making the surviving fragments of open fen unsuitable for the butterfly’s food plant milk parsley (Peucedanum palustre).

Natural recolonisation of the species seemed unlikely as the only other population of the unique British race britannicus occurred 160km to the north in the Norfolk Broads. Numerous attempts were made to reintroduce the butterfly from Norfolk but all failed as there appeared to be insufficient quantities of milk parsley on the Fen.

A more concerted and scientific attempt was undertaken beginning in 1974 when over 2000 milk parsley plants were planted around the Mere on Adventurers’ Fen. Although many plants were lost to duck grazing, adults bred in captivity at Monks Wood Experimental Station from Hickling Broad stock, 124 females and 104 males, were released on the Fen in 1975. It was estimated that these adults laid over 20,000 eggs and that 2000 caterpillars pupated (Dempster 1976 and Dempster, King and Lakhani 1976). Unfortunately, after this promising start, the number of milk parsley plants plummeted, and swallowtails were extinct again by 1980. Much research into the ecology of milk parsley was undertaken during the 1970s and 1980s to try and gain an understanding of how the Fen might be managed for the benefit of swallowtails and milk parsley (see Meredith 1976 and Harvey and Meredith 1981)

One final attempt to re-introduce swallowtails was made, when captive-bred Norfolk-sourced larvae were released onto the Fen. Unfortunately several years of summer droughts produced poor milk parsley growth and the swallowtail was extinct again by 1996. No further attempts have been carried out and none are proposed as, at the present time, significant areas of suitable habitat are still not available, and it has still not proven possible to re-establish pre-drainage water levels on the Fen.

Pale clouded yellow (Colias hyale) Both Farren (1923 & 1926) and Fryer (1938) record pale clouded yellow – ‘common in years when there are considerable migrations’. However there have been no records since. Pale clouded yellows look almost identical to the helice form of clouded yellow. Maitland Emmet and Heath (1990) discuss the difficulty of accepting early records of pale clouded yellow – ‘none of these specimens now exist and any or all of them may have been misidentified as Colias croceus f. helice.’

Clouded yellow (Colias croceus) Clouded yellows are recorded in most years during warm weather when influxes of the species from the continent occur. Most records are between May and September. 

Brimstone (Gonepteryx rhamni) The brimstone is one of the commonest species on the Fen and has been recorded in every month. The widespread distribution of its foodplants – the buckthorn (Rhamnus cartharticus) and alder buckthorn (Frangula alnus) on the Fen explains its abundance.

Large white (Pieris brassicae) The large white is commonly recorded on the Fen in May and June and between July and September. Most commonly the species is found in the edge of the Fen nearest the village.

Small white (Pieris rapae) A very common species recorded from May through to September.

Green-veined white (Pieris napi) Very common on the Fen with more individuals being recorded during their second flight period between July and September.

Orange tip (Anthocharis cardamines) This species is fairly common throughout the Fen. It appears to be recorded most frequently on the Fen edge but has been recorded in the Sedge Fen and St Edmund’s Fen.

Green hairstreak (Callophrys rubi) Green hairstreaks are recorded every year from Sedge and Verrall’s Fens but numbers are small as the species is easily overlooked. It is thought that the foodplant for this species at Wicken is the buckthorn.

Purple hairstreak (Quercusia quercus) The purple hairstreak was first recorded at Wicken Fen on 29th July 2004 by National Trust warden Ralph Sargeant in compartment 15, by an oak tree on the boardwalk. One was also recorded in 2005, on the same tree.

White–letter hairstreak (Strymonidia w-album) The only record for this species at Wicken occurs in Fryer’s account in the Victorian County History in 1938. No date, specific location or recorder is given. Today at Wicken there is an old hedge of elm (the caterpillars’ foodplant) alongside compartment 23, in the northwest edge of the reserve. This would warrant searching during July and August as this elusive hairstreak may recolonise the Fen as it is again spreading in some areas after the population declines following the ravages of Dutch Elm Disease.

Small copper (Lycaena phlaeas) Each year only a few individuals are recorded. The species breeds on the Fen at very low densities.

Large copper (Lycaena dispar) Prior to the 1850s the large copper (Lycaena dispar dispar), the native race, lived in the Fens from Lincolnshire to Cambridgeshire as well as in Norfolk. However, following the major drainage schemes the species became extinct in Britain in 1851, when Whittlesey Mere in Huntingdonshire was drained. It had been assumed that the species had been long since extinct in Cambridgeshire but in that year a specimen was also recorded on Bottisham Fen.

There is no direct evidence to link the native race of large copper to Wicken Fen, although 19th century accounts refer to the species being present ‘near Ely’ and ‘Cambridge’. However in 1909 the renowned entomologist GH Verrall attempted to introduce the large copper to Wicken Fen using the race rutilus collected from near Berlin (Salmon 2000). This attempt failed and J Stanley Gardiner reporting on the matter in 1932 stated that it had been introduced ‘where it had formerly been abundant but had died out, probably killed in the fires of the last century’ (Stanley Gardiner 1932a).

In 1930 another attempt to introduce the large copper was made this time using the race batavus collected in the Netherlands. Prior to the animals being released a large number of water dock Rumex hydrolapathum, the caterpillars’ foodplant, was planted on Verrall’s Fen in 1929-30. This attempt was successful as the species spread over the Fen including Adventurers’ Fen (Eastham 1932). However when Adventurers’ Fen was drained in the 1940s the species was lost again. No further attempts have been carried out and none are proposed. Research is however being conducted in the Norfolk Broads which indicates that the species requires much larger areas of suitable habitat than currently exist at Wicken Fen (Pullen pers comm).

Brown argus (Aricia agestis) This species was originally recorded by Farren in his 1926 list. It was not recorded again until 1997. It is now recorded annually on Little Breed Fen compartment 23.

Common blue (Polyommatus icarus) Common blues are recorded annually on the Fen but is commonest on the Fen edge on dry areas such as Breed Fen where its food plant occurs..

Holly blue (Celastrina argiolus) A common species on the Fen. Its eggs are laid on holly (Hedera helix).

White admiral (Ladoga camilla) The only record for this species occurs in the recent checklist for the Fen (Friday and Harley 2000) where it states that one individual was seen in 1989. This is a woodland species dependent on honeysuckle and therefore the 1989 was a casual record.

Red admiral (Vanessa atalanta) This is a migrant species which can occur in large numbers on the Fen in peak years. Commonly seen feeding on hemp agrimony (Eupatoria cannabinum).

Painted lady (Cynthia cardui) Another migratory species which is usually less common that red admiral. 2003 saw a huge influx of this species on the Fen (and in the UK generally).

Small tortoiseshell (Aglais urticae) This is a common breeding species on the Fen – at times it is the commonest butterfly. In August 1997 1523 individuals were counted on a single day.

Large tortoiseshell (Nymphalis polychloros) Farren (1926) includes this species in his Wicken Fen list, however no further details are available. The species is now extinct in the UK.

Peacock (Inachis io) A common butterfly on the Fen which can be recorded in most months (see photo, right).

Comma (Polygonia c-album) This species is recorded annually on the Fen, most usually on Little Breed Fen. It is not, however, a common species.

High brown fritillary (Argynnis adippe) There is one record for high brown fritillary, recorded by Raynor and reported in the Entomologist in 1882.

Dark green fritillary (Argynnis aglaja) Farren includes dark green fritillary in his 1926 list and it would appear that this involves a single record from 1923 (Fryer 1938). Between 1985 and 1992 only one dark green fritillary was seen in all of Cambridgeshire (Bennett and Perrin 1994).

Marsh fritillary (Eurodryas aurinia) The status of marsh fritillary at Wicken Fen is a little tenuous. Early accounts of the species from the 1800s talk about the species being present at ‘Swaffham Bulbeck’, ‘at Ely’, ‘at Burwell Fen’. Farren however does not even include the species on his list of Wicken species in 1926, and in his 1923 account he says marsh fritillary ‘also occurred in various parts of the fens, but has not been recently recorded’.

It is only Fryer’s 1938 account in the Victorian County History where the marsh fritillary is actually linked with Wicken Fen – ‘Wicken 1 (C. de Worms, 1922)’ i.e. one specimen was taken by Baron Charles de Worms (a famous butterfly and moth collector) in 1922.

Smart (1972) does not mention the existence or extinction of marsh fritillary whilst curiously the account in Friday 1997 p127 states ‘the extinction at the Fen in the early 1940s of the marsh fritillary passed almost without comment. All the other accounts link the extinction of the species at Wicken with the de Worms record in 1922.

It is therefore not clear whether the species was a regular resident on the Fen from the mid 1800s – if it was, why are there no records and no specimens in collections? Perhaps the species had died out before this and the de Worms record represents a vagrant animal from a nearby area of suitable habitat, possibly the ‘Burwell Fen’ records mentioned in the earlier accounts which is less than one mile from the Sedge Fen. Either way it would be very interesting to discover more about this species at Wicken Fen. Today its food plant devil’s bit scabious (Scabiosa succisa) flourishes in profusion on the autumn-cut ride sides, making Wicken Fen a potentially suitable site for a re-introduction if ever the recolonisation of East Anglia by marsh fritillary was thought appropriate.

Speckled wood (Pararge aegeria) Bennett in 1984 noted that only a single individual had been recorded on the Fen in May that year at the northern eastern end of Sedge Fen Drove. The species has now successfully colonised Wicken Fen as Bennett speculated that it might. Speckled wood is now a common species in the shady scrubby parts of the Sedge Fen, St Edmunds Fen, Verrall’s Fen and Breed Fen.

Wall (Lasiommata megera) Bennett stated that the wall was ‘apparently increasing throughout the reserve from an already healthy position’.

There were nine records of the species in 1998 but by 2004 only occasional individuals were recorded. This major decline at Wicken Fen appears to mirror the national trend (Mathew Oates pers comm). It will not be surprising if the species is extinct at Wicken within a decade if this trend continues. Unfortunately it is not at all clear what is causing this decline.

Marbled white (Melanargia galathea) Two individuals were recorded on 6th July 1946. These are the only records. Marbled whites do inhabit the Devil’s Ditch near Reach so they may have been vagrants from that population.

Gatekeeper (Pyronia tithonus) This is a common species particularly on the drier parts of the Fen. (see photo, right)

Meadow brown (Maniola jurtina) Common throughout the Fen. The species appears to have increased in recent years and spread from the drier margins to the wetter centre of the site.

Small heath (Coenonympha pamphilus) Originally described by Bennett (1984) as rather localised it can now be called very uncommon, with only a handful of records each year from the Sedge Fen and Little Breed Fen.

Ringlet (Aphantopus hyperantus) In 1979 the ringlet was found in only a ‘handful of tiny discreet colonies around the edge of the Sedge Fen’ (Corbet et al 1997). Since then the species has expanded considerably and today can be found on the Sedge Fen, Verrall’s Fen, St Edmund’s Fen and Breed Fen.

Monarch (Danaus plexippus) One individual of this American vagrant was seen in 1992.

References, source documents and further reading

Bennett T (1985) The butterflies at Wicken Fen – a current annotated checklist. NT
Bennett T & Perrin V
(1994) T he butterflies of Cambridgeshire: highlights of a county survey (1985-1992) Nature in Cambridgeshire no. 36.
Corbet SA, Dempster JP, Bennett TJ, Revell RJ, Smith CC, Yeo PF, Perry I, Drane AB & Moore NW (1997) Insects and their conservation pp123-143. In Friday (1997).
Dempster JP (1976) The swallowtail butterfly at Wicken Fen. Nature in Cambridgeshire 19: 11-14.
Dempster JP, King ML & Lakhani KH (1976) The status of the swallowtail butterfly in Britain. Ecological Entomology 1: 71-84.
Eastham LES (1932) Wicken Fen fauna – a review pp630-636. In Stanley Gardiner (1926).
Farren W (1904) The lepidoptera of Cambridgeshire. pp161-172. In Marr and Shipley (1904)
Farren W (1923) The lepidoptera of Cambridgeshire pp53-64. In Stanley Gardiner and Tansley (1923)
Farren W (1926) A list of the lepidoptera of Wicken and the neighbouring fens pp258-266. In Stanley Gardiner (1926)
Friday L & Harley B (2000) Checklist of the flora and fauna of Wicken Fen. Harley Books.
Friday L. (1997) Wicken Fen: the making of a wetland nature reserve. Harley Book.
Fryer JCF (1938) Lepidoptera pp139-161. I n Imms AD (1938)
Gardiner BOC (1963) The butterflies of Cambridgeshire. Nature in Cambridge no. 6.
Harvey HJ & Meredith TC (1981) The biology and conservation of milk parsley at Wicken Fen. Nature in Cambridgeshire 24: 38-42.
Imms AD (1938) Zoology of Cambridgeshire. Victorian County History vol. 1.
Maitland Emmet A & Heath J (1990) The butterflies of Great Britain and Ireland vol 7 pt 1. The moths and butterflies of Great Britain and Ireland. Harley Books.
Marr JE & Shipley AE (1904) Handbook to the natural history of Cambridgeshire. CUP
Meredith T (1976) The food plant of the swallowtail butterfly: experiments at Wicken Fen. Discussion Papers in Conservation No.12. University College London.
Salmon M (2000) The Aurelian Legacy. Harley Books
Smart J (1972) Butterflies and day flying moths. Guides to Wicken Fen no. 8, Wicken. NT. (See below, for comparison)
Stanley Gardiner J & Tansley AG (1923) The Natural History of Wicken Fen part I. Bowes and Bowes Cambridge
Stanley Gardiner J (1926) The Natural History of Wicken Fen part III. Bowes and Bowes Cambridge.
Stanley Gardiner J (1932) The Natural History of Wicken Fen part VI. Bowes and Bowes Cambridge
Stanley Gardiner J (1932a) Omissions and additions pp644-648. In Stanley Gardiner (1926)

Butterflies
Wicken Fen Guides No 8

John Smart, 1972

Wicken Fen, when we refer to the National Trust property now managed as a nature reserve, is a comparatively restricted and easily defined area comprising Wicken Sedge Fen, St Edmund's Fen and Adventurers' Fen. Wicken Poors' Fen is usually also regarded by naturalists as part of the whole complex. The Fen lies adjacent to the village of Wicken in Cambridgeshire. Many of the older records of Lepidoptera on the Fen are merely 'Wicken', and this term probably covers a much wider area than the area now constituting the National Trust reserve. It can com prise, in addition to the present reserve, Burwell Fen, now completely taken over by intensive agriculture, and South Adventurers' Fen, beyond the Burwell Lode, which was totally reclaimed for agriculture during the 1939-45 war. It is also perhaps worth noting that the present Adventurers' Fen has sometimes in the past been regarded as part of the old Burwell Fen; it has also been designated 'North Adventurers' Fen'.

Wicken has long been famous for its Lepidoptera and many Lepidopterists have at one time or another collected there. Unfortunately, while there must be many specimens from Wicken in collections of butterflies and moths, not much has been recorded in print except when rarities of one kind or another have been captured.

Farren, in 1926, published a list of Lepidoptera from Wicken and the neighbouring.Fens but this list contains no dated records and the Farren collection has been dispersed. Consequently we cannot date accurately certain changes that have taken place in the butterfly fauna of the Fen. In the last few decades the Large Tortoiseshell and the Dark Green Fritillary have vanished and the immigrant Clouded Yellows have not been seen for some time past. Farren listed the Brown Argus (Aricia agestis Sclnfm. = Chrysophanus astrarche in Farren's list) but this butterfly has not been seen on the present reserve and would not be expected there other than as a wind-blown stray from some area of chalk grassland; its usual larval food plants are not found on the Fen. The local Wicken population of the Swallowtail died out around 1950. There are, however, credit entries on the balance sheet, and we find that Farren did not record the Comma, Holly Blue, Grizzled Skipper, Dingy Skipper, or, curiously, the Small Tortoiseshell in his list.

Agricultural practice in the vicinity of Wicken Fen is now very intensive indeed. This condition came about during and since the 1939-45 war. There is less rough ground left for insects to inhabit, and modern practices, with the use of pesticides of one kind or another, have reduced the numbers of some butterflies such as the Whites, which are a pest of cruciferous crops in field and garden. Weeds (e.g. Nettles) which are the food plants of many caterpillars have also been reduced. Improved drainage in surrounding areas may also be making the Fen more accessible to insects typical of the drier land that rises at the margins of the Fens.

Of the butterflies that are listed below probably only a few are typically Fenland butterflies. By this is meant butterflies that would be found on the Fen if it were surrounded by wide areas of similar vegetation and was not itself much modified in parts by past and current management practices. The Reed-beds, the Sedge-fields and the Carr thickets can be considered as typical; the droves cut through the Fen, which are subjected to a programme of mowing to encourage flowers as well as to provide access, are 'artificial' and would revert to Reed-bed, Sedge-field or Carr if not trodden and mown. A great many of the buttcrffics of the present day Fen will be found in these droves. Typical Fen butterflies are the Swallowtail, the Brimstone, the Green Hairstreak and the now extinct Large Copper; perhaps the Holly Blue and the Dark Green Fritillary should be added to this short list.

The Swallowtail butterfly is the Fen's most famous insect. Once plentiful on the Fen, the Wicken population died out around 1950. Two factors are believed to have contributed to this but there may be other factors that have not yet been identified. These factors are: the reduction in the areas managed as Sedge-fields, with the development of extensive areas of Carr, reducing the availability of food plant for the caterpillar and of nectar flowers for the adult butterflies; over- collecting of the insect in all its stages. Efforts are being made to re- introduce the Swallowtail, using laboratory-reared stock coming originally from the Norfolk Broads. These introductions are coupled with management to provide areas in which both the larval food plant and nectar flowers will be available; and, of course, a total ban on collecting the species in any of the stages of its life-history.

A similar attempt, before the 1939-45 war, to introduce a Continental race of the Large Copper - long extinct in the Fens - unfortunately failed.

Lepidoptera may not be collected in the Fen without a written permit. Initial inquiries for such permission may be made in writing to the Property Manager, Wicken Fen, Wicken, Cambs. At one time recording of species was almost totally dependent on the capture of specimens and getting them into collectors' cabinets or store-boxes. Nowadays more and more reliance is being placed on accurate field identification, and the camera is replacing the butterfly net. No permit is needed for the use of a camera for this purpose!

Because of the long term changes in the butterfly population of the Fen, and the annual differences between 'good' and 'bad' years for individual species, the National Trust are always glad to receive records of species seen on the Fen, if these are based on sound identification. Any such list of species should be sent to the Property Manager or the Zoological Secretary of the Wicken Fen Local Committee, whose address is Department of Zoology, Downing Street, Cambridge.

Butterflies can be identified either by looking at named specimens in a collection or by the use of books. Access to the former depends on circumstances. Of books, there is a wide variety of the reliable elementary type. South, R. The Butterflies of the British Isles, Wame, London, first published in 1906 but still kept in print in revised editions, is now almost a classic written from the collector-naturalist point of view. As an introduction to the study of butterflies as living animals in their environment, it will be some time before Ford, E. B. 1945, Butterflies, New Naturalist Series no. 1, Collins, London, is bettered. A recent book that is likely to remain authoritative for many years is Higgins, L. G. and Mey, N. D. 1970, A Field Guide to the Butterflies of Britain and Europe, Collins, London; anyone whose interest in butterflies is likely to extend beyond the British Isles should probably " to invest in a copy of this book without delay. The names used in this guide are in accordance with Higgins and Riley.

In a publication of this kind notes on individual species must he very brief. Information given is mainly about the imagines or adult butterflies since these are the stages most frequently seen by visitors to the Fen. Food plants utilised by the larvae (caterpillars) are mentioned. There is nothing about the pupae or the eggs except when these are mentioned in the table as over-wintering stages.

Acknowledgements

The author wishes to acknowledge help received in the preparation of this guide, from.

Dr J. P. Dempster; Lt-Col A. M. Emmet; Mr B. 0. C. Gardiner; Dr J. D. Holloway; Mr P,. Northfield; Mr P. D. Sell; Mr H. L. G. Stroyan; Dr S. Max Walters; The Biological Records Centre (Monks Wood Expt. Stn) and Mrs Judith North.

References

Farren,W. 1926 A list of 1epidoptera of Wicken and the neighbouring Fens. In Stanley Gardiner, J. The Natural History of Wicken Fen. (Pt 3):258-266.
More recent county lists are:
Fryer, J. C,. F. and Edelston, H. M. 193 8. Lepidoptera. In Victoria County History of Cambridgeshire and the Isle of Ely, 139-161.
Gardiner, B. 0. C. i963. ne Butterflies of Cambridgeshire. Cambridge Naturalist, 6: 1-6
An older but relevant list is:
Balding, J. 1878. Lepidoptera. In Miller, S. H. and Skertchley, S. B. J. The Fenland: Past and Present, 401- 412. 591-633.

The Butterflies

PAPILIONIDAE

SWALLOWTAIL (Papilio machaon L.). At one time common. Specimens seen on the Fen now are all from introduced laboratory-reared stock that originally came from the Broads. Typically found flying over Sedge-fields and along Droves seeking sites for egg-laying or neetar- bearing flowers. Larvae feed on Peucedanum palustre (Hog's Fennel, Milk Parsley or, locally, 'The Carrot') and some other Umbellifers.

The Swallowtail could be regarded as the typical butterfly of the Sedge-fields on the Fen.

PIERIDAE
LARGE WHIT.E (Pieris brassicae L.). A pest of cabbage and similar crops; now less common than previously. Comes into the Fen from fields and gardens. Two or three overlapping broods in the year. Larvae feed on cruciferous crops, garden plants and weeds.

SMALL WHITE (Pieris rapae L.). Common, many probably coming on to the Fen from fields and gardens. Several overlapping summer broods. Larvae feed on cruciferous crops, garden plants and weeds.

GREEN-VEINED WHITE (Pieris napi L.). Common and more at home on the Fen than the Small White; many probably come on to the Fen from fields and gardens. Several overlapping summer broods. Larvae feed on Rape and other cruciferous crops, garden plants and weeds.

ORANGE TIP (Anthocaris cardamines L.). Common on the Fen and often one of the first butterflies to be noticed on the Droves in the spring. Females lack orange colouration and look like a Small or a Green- veined White. Larvae feed on cruciferous plants of various kinds, especially the weeds Alliaria petiolata (Jack-by-the-Hedge or Garlic Mustard) and Sisymbrium officinalis (Hedge Garlic or Hedge Mustard) and on Cardamine pratensis (Cuckoo-flower or Lady's Smock). Upon the flower-heads of the last named, the butterflies will often be found resting.

CLOUDED YELLOW (Colias crocea Geoff.) and PALE CLOUDED YELLOW (Colias hyale L.). Rare on the Fen only occurring in years when there has been an exceptionally good immigration into England from Europe. May be a number of summer broods. Larvae feed on leguminous plants.

BRIMSTONE (Conepteryx rhamni L.). This bright yellow butterfly is common on the Fen. Can be mistaken for Swallowtail at a distance but is usually found around the Carr rather than on the Sedge-fields. Larvae feed on Buckthorn and Alder Buckthorn. The Brimstone could be regarded as the typical butterfly of the Carr on the Fen.

NYMPHALIDAE
LARGE TORTOISESIIELL (Nymphalis polychloros L.). This butterfly underwent a drastic reduction of its range early in the present century. It used to be recorded as present on the Fen but now is almost certainly absent. The over-wintered spring generation is the one usually seen rather than the summer one. Larvae feed on Elm, Willow and other trees.

PEACOCK (Inachis io L.). Common, but more often seen in the late summer and early autumn rather than early in the season, when the overwintering adults emerge from hibernation. Larvae feed on Nettles (Urtica dioica).

RED ADMIRAL (Vanessa atalanta L.). Sometimes very common indeed in the late summer when it with be seen, with Peacocks, Commas, Small Tortoiseshells and, perhaps, Painted Ladies on the flowers of the Buddleia bushes in front of the William Thorpe Building at the entrance to the Fen. Larvae feed on Nettles.

PAINTED LADY (Vanessa cardui L.). In a good immigration year this butterfly may be quite plentiful in the late summer. Larvae feed on Nettles and Thistles.

SMALL TORTOISESHELL (Aglais urticae L.). This common countryside butterfly may even be found flying in late autumn and very early spring when warm weather tempts hibernating adults out of their winter quarters. Larvae feed on Nettles.

COMMA (Polygonia c-album L.). Before the 1914-18 war, this butterfly was regarded as a West of England species and it was not recorded from the Fen. Since that time it has greatly extended its range and is now present at Wicken. As in the case of the Small Tortoiseshell, individual butteries may be found flying in late autumn and very early spring if warm weather stimulates the hibernating adults. Larvae feed niaiffly on Nettles.

DARK GREEN FRITILLARY (Mesoacidalia aglaja L.). This beautiful, fast- flying and agile butterfly has not been seen in recent years on the Fen although it was known at Wicken in the past. It has always been localised in its distribution and, being a strong flier, it might well re-colonise the Fen if circumstances favoured this. It settles on Thistles and other flowers.

The preferred food plant of the larvae is stated to be the Dog Violet (Viola canina), and this has not recently been seen on the Fen. The larvae also feed on Common Milkwort (Polygala vulgaris) and probably on other violets, but no violets are as common now as they once were when peat-cutting was practised on the Fen.

SATYRIDAE
MEADOW BROWN (Maniola jurtina L.). This is typically a butterfly of grassland in open spaces in woods and other places; it is, however, very common and finds its way on to the Fen. Larvae feed on Smooth- stalked Meadow Grass and other grasses.

RINGLET OR HEDGE BROWN (Aphantopus hyperatitus L.). A common woodland butterfly that frequents lanes, droves and clear areas where growths of trees abut on these. It has a preference for some shade but will come into the full sun to take nectar from Bramble flowers or the like. Larvae feed on grasses.

SPECKLED WOOD (Pararge aegeria L.). Essentially a woodland butterfly, this species is most likely to occur in places on the Fen where a growth of trees abuts on a lane, drove or other open area. It has a long flight season, but this may be due to delayed emergence on the part of some specimens, as well as there being several broods in the course of the summer. Larvae feed on grasses, especially Couch Grass.

GATEKEEPER (Pyronia tithonus L.). A butterfly of very similar habits to the Meadow Brown but not as common. The caterpillar occurs on a wider variety of grasses.

SMALL HEATH (Coenonympha pamphilus L.). Typically this is a common butterfly of drier areas than the Fen. The adults have a long flying period from May to September inclusive; this is probably due to the population consisting of a mixture of races with different lengths of life-cycle and the occurrence of a second brood in some cases. Larvae feed on grasses.

WALL BROWN OR WALL (Lasiommata megera L.). Another typically grassland butterfly that finds its way on to the Fen. Larvae feed on grasses.

LYCAENIDAE
GREEN HAIRSTREAK (Callophrya rubi L.). This is a small and inconspicuous butterfly and it may be commoner on the Fen than sightings suggest. The caterpillars are stated to feed on a variety of plants and of these, Buckthorn, Alder Buckthorn and Bramble are common on the Sedge Fen and elsewhere.

SMALL COPPER (Lycaena phlaeas L.). There are probably up to three broods of this brilliant little butterfly in the course of the year. It will usually be found moving from one flower-head to another seeking nectar. Larvae feed on Docks and Sorrels.

LARGE COPPER (Lycaena dispar Haw.). Long extinct in the Fens but still mentioned in books on British butterflies.

BROWN ARGUS (Aricia agestis Schffm.). Listed by Farren (1926); see comment in Introduction.

COMMON BLUE (Polyommatus icarus Rott.). Flower heads of Thistles are a frequent resting place for the butteries where they take up nectar from the flowers. Not typically a Fen butterfly it will, howevery be found on the Fen throughout the flight season. Larvae feed on leguminous plants.

HOLLY BLUE (Celastrina argiolus L.). Normally associated with Holly and ivy, which are the common food plants of the caterpulars; the Fen population probably feeds on Spindle, Alder Buckthorn, Ivy and Brambles. Much commoner in some years than in others.

HESPERIIDAE
GRIZZLED SKIPPER (Pyrgus malvae L.). The pale yellow flecking on the dark brown wings will distinguish this Skipper from the others that may turn up on the Fen. With all Skippers flight is rapid and they can be mistaken for moths by those not familiar with them. Larvae feed on Wild Strawberry, Potentilla species and other plants.

DINGY SKIPPER (Erynnis tages L.). This is the most moth-like of the Skippers in its field behaviour. Usually associated with chalk (or limestone) areas it can find its way on to the Fen from neighbouring localities. The larvae feed on Bird's Foot Trefoil (Lotus corniculatus).

ESSEX SKIPPER (Thymeticus lineola Och.). This species is stated, in the literature, to occur on the Fen. It is very like the Small Skipper and the adults have similar habits. Larvae feed on grasses.

SMALL SKIPPER (Thymelicus svlvestris Poda). This small butterfly will be found in the grassy areas of the Fen, frequently perched on the flower-heads of Thistles and the like. Larvae feed on grasses.

LARGE SKIPPER (Ochlodea vetiatus Brem. and Grey). This species is slightly larger than the other Skippers mentioned above; it is of the same brown colouration as the Small and Essex Skippers but there are yellow markings on the wings in both sexes that distinguishes it from them. Larvae feed on grasses.

National Trust
Wicken Fen, Lode Lane, Wicken, Ely, Cambridgeshire, CB7 5XP, UK
Tel/Fax: (+44) (0)1353 720274 | Email: wickenfen@nationaltrust.org.uk