Seeing butterflies flitting around a deciduous woodland – not that you’d be likely to find them flitting around one of the grim coniferous woodlands planted in the mid-20th century – is almost as good as seeing them across downland. The species, of course, tend to be different, but similarly several are under threat, none more so than the Pearl-bordered Fritillary (Boloria Euphrosyne, wingspan 45mm).
One of the earliest Fritillaries to appear, sometimes in April, the species has undergone a 66 per cent decline in the last 20 years or so despite colonies having as many as 100 adults and being capable of dispersal within a range of 5km. The south-east has done as poorly as anywhere.
The foodplant of the caterpillars is principally Common Dog Violet (Viola riviniana), which is not so common as it used to be because of a reduction in management techniques, especially not maintaining flower-rich woodland rides and clearings.
This obviously has not helped the Pearl-bordered Fritillary, any more than it has helped the High Brown Fritillary (Argynnis adippe, wingspan 65mm), a fast flier which used to be found in most counties in south-east England with good stands of woodland but is now extinct here and seen only further west. The map on the National Biodiversity Network Gateway website shows the decline all too clearly. (The NBN Gateway is a first-rate source of information about British wildlife of all kinds over the last few centuries.) For the record, the High Brown Fritillary used to reside in woodland clearings, often with the Bracken which is now an essential part of its habitat in the west country.
Given the decline of these two species which use Dog Violet, the continuing success of another butterfly requiring the same plant for its caterpillars, the impressive Silver-washed Fritillary (Argynnis paphea, wingspan 72mm), is a bit peculiar as well as being very welcome.
The Heath Fritillary (Melitaea athalia, wingspan 44mm) is much more specific in its requirements and much rarer than the Pearl-bordered or the High Brown – all three are priority species under the Biodiversity Action Plan – but at least it is not declining. Blean Woods in Kent, a reserve of the Royal Society for the Protection of Birds, which is managed for all forms of wildlife, is the only place east of Devon to see them.
The foodplant is Common Cow-wheat (Melampyrum pratense), which requires acid soils and is far from common, though Foxglove and Ribwort Plantain can be used. Coppicing is essential to encourage the growth of the Cow-wheat, and as the butterflies are sedentary, and suitable habitats are so fragmented, there is little chance of any expansion of range in the foreseeable future.
While on the subject of rarities and extinctions, the Chequered Skipper (Carterocephalus palaemon, wingspan 30mm), arguably the most dashing skipper of them all in colouration, became extinct in England in 1976 and is now found only in western Scotland. Chequered Skippers were never so common as High Brown Fritillaries but they were found in Bedfordshire and Hampshire as well as in larger numbers in Northamptonshire and Lincolnshire, using False Brome (Brachypodium sylvaticum) as the foodplant. The habitats were clearings and rides in old coppiced woodland and some limestone grassland. The decline of woodland management from 1960 onwards must have been a factor for this species.
The Wood White (Leptidea sinapis, wingspan 44mm) is the smallest of the white group of butterflies and much the rarest. A species whose weak flight makes it unmistakable, it is a BAP priority species whose numbers and range have declined gravely in the last 20 years. The foodplants are fairly common legumes, principally Meadow Vetchling (Lathyrus pratensis), Bitter-vetch (Lathyrus linifolius), Tufted Vetch (Vicia cracca) and Birdsfoot Trefoil (Lotus corniculatus) though not Common Vetch (Viccia sativa). Similarly, the required habitat is not exactly in short supply since Wood Whites, which fly in June, utilise mainly woodland rides and clearings but also some coastal sites and field edges. In Ireland, where the species is thriving, they even use road verges and hedges, so the decline in Britain is rather odd.
The Brown Hairstreak (Thecla betulae, wingspan 38mm), like the Black Hairstreak (Strymonidia pruni), uses young Blackthorn (Prunus spinosa) as its foodplant and is another Biodiversity Action Plan priority species. The removal of hedges after World War II and the unhelpful policy of flailing them every year, which removes the butterflies’ eggs, appear to have had an effect.
Equally, Brown Hairstreaks, which are visible in August, are elusive. They spend most of their time in the tree canopy, especially on the ‘master’ Ash (Fraxinus excelsior), so there may be more colonies to be found even now. And although young Blackthorn might have been in short supply for much of the last two decades, proper hedge management and planting suggest this butterfly may enjoy a resurgence.
Dutch Elm Disease in the 1970s caused ruination to one of our best-loved native trees, and didn’t do much for the White-letter Hairstreak (Strymonidia w-album, wingspan 36mm) since elms, mainly Wych Elm (Ulmus glabra), are its foodplant. Fortunately, enough elm suckers have the ability develop over the space of several years before being infected by the beetles to allow the butterfly to carry on breeding, but it is undoubtedly much more vulnerable than formerly and became a BAP priority species in 2007.
The Green Hairstreak (Callophrys rubi, wingspan 33mm), seen in May and June, is much commoner than the others on this page, mainly because it is adaptable in the foodplants used, which can vary from Gorse (Ulex sp) to Dogwood (Cornus sanguinea) and Birdsfoot Trefoil. Their camouflage in a hedgerow is remarkable.
The commonest hairstreak is the Purple Hairstreak (Quercusia quercus, wingspan 36mm), which is seen in July and August. As its scientific name suggests, the species relies on Oaks (Quercus sp) for breeding and the adults spend most of their time perched or flying around ‘up top’, with occasional sorties to ground level for nectaring.
The White Admiral (Ladoga camilla, wingspan 60mm) and the sallow-feeding Purple Emperor (Apatura iris, wingspan 78mm) are the royalty of woodland butterflies. White Admirals are commoner, seen nectaring principally on brambles in July but using Honeysuckle (Lonicera periclymenum) as the foodplant.
The Purple Emperor, a species of conservation concern which has stabilised following a decline in the 20th century, is second only to the Swallowtail in size among British butterflies. Restricted to Oak woodland, it spends most of its time up in the canopy but does come down to drink at puddles or obtain minerals from dung. The blue/purple colouring on the wings is visible only in sunlight due to refraction.
Peacocks (Inachis io, wingspan 65mm) are among the best-known of all our butterflies, thanks to their colouring, size and omnipresence. The adult female can lay up to 500 eggs on Stinging Nettles (Urtica dioica) in May with the resulting caterpillars, which put on a stunning apearance in their black livery, feeding gregariously and often reducing fair-sized patches of the foodplant to a series of virtual skeletons.
Pupation occurs in July and the next generation emerges in August before pretty quickly getting down to hibernating, often inside hollow trees. They reappear in the spring when the process starts all over again.
The same overwintering method is used by two other Nettle-feeding butterflies, one of which is under unexpectedly severe pressure. The Small Tortoiseshell (Aglais urticae, wingspan 50mm) always used to be one of the commonest of the group everywhere, including in gardens, but it has suffered a dramatic decline lately, with an 80 per cent fall in numbers since 1990. Theories that this collapse is due to climate change are unconvincing – the Peacock has not suffered the same decline, while the Comma (see below) is expanding its range – and a much likelier explanation is the parasitoid fly Sturmia bella, first seen in the UK in Britain in 1999.
This fly’s eggs are regularly found on Nettles alongside Small Tortoiseshell caterpillars and one theory is that the caterpillars eat these eggs which hatch inside them when they are cocoons and proceed to consume the host. Sturmia bella is a mainland Europe species, where it seems not to have anything like such a negative effect. One possible reason for optimism was the arrival in England in August-September 2008 of a massive influx of adult Small Tortoiseshells from the continent. Dorset was particularly strongly affected. With any luck these migrants will have added significantly to the breeding stock.
Another butterfly which overwinters as an adult and relies principally on Nettles as a foodplant (though Hop, Humulus lupulus, is also used) is the Comma (Polygonia c-album, wingspan 55mm). Named after a white mark on the hind wing, this is the only British species with uneven wing edges. Commas can be seen for much of the year since the overwintering adults emerge in September and can last until April, producing a July brood. Interestingly, the Comma is expanding northwards and in fact has done exceptionally well considering it experienced a mysterious and serious decline in the late 19th century.
The warmer winters experienced in Britain in recent years have enabled another Nettle feeder to start hibernating successfully in places. This is the Red Admiral (Vanessa atalanta, wingspan 65mm), which formerly never survived the attempt at hibernating in cold conditions.
That failing never impaired the possibility of seeing this handsome species though, since thousands successfully migrated here from their southern European stronghold every spring, as they continue to. This is normally from late April onwards, so it is a fair assumption that the pictured butterfly, photographed at the end of March 2007, had overwintered here. Whatever the dangers of climate change, some invertebrates in particular are likely to profit.
Orange Tips (Anthocharis cardomines, wingspan 45mm) are decidedly common, but none the worse for that. Among butterflies that do not overwinter as adults, it is one of the first to appear in the spring, sometimes in March and often lasting through until June.
They use Lady’s Smock (Cardamine pratensis) or Garlic Mustard (Alliaria petiolata) as the foodplant, so well-managed hedgerows and even verges benefit them. The female does not have any orange colouring.
We can close with the species perhaps most often seen in woodland, though one that’s none too easy to keep track of as it flits about at speed in the dappled light along rides and margins – the Speckled Wood (Pararge aegeria, wingspan 48mm). Lack of management in woodland for most of the last 50 years has probably helped them in so far as shadier areas are more numerous now. The caterpillars feed on grasses.
Images © Jeremy Early. All rights reserved.