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HEATHLAND MOTHS PAUL WARING I would like to introduce some of the moths that may be found on heathland, describe a little bit about their biology and make some key points regarding heathland moths and about heathland management issues as they affect moths and other invertebrates. These moths can be considered as a 'flagship' group for all the other invertebrates for which heathland is their only, or only major habitat. They are the species that are going to benefit most from the conservation of our remaining heathland and for which re-creation of heathland may be particularly beneficial. General overview One of the features that reveals itself when heathland invertebrates are studied is the extent to which heathland habitats form a continuum. In some cases moths seem to have as much difficulty recognising heathland as people do. There are species that are closely associated with heathlands in the strict sense, as lowland Vegetation dominated by dwarf shrubs, particularly ericaceous species, and others that occur in a wider ränge of habitats. There are moths that are widely recognised as heathland species that are found in relatively few heathland habitats, but which also occur on chalk downland. This pattern of distribution reveals something of the way that moths approach heathland. For many species, the key requirements are hot, low-lying places, usually with dry areas and often with micro-climates that are measurably hotter than their associated local climates. Often these micro-climates are more typical of climates recorded at latitudes many miles further south. The acidity, or even the presence of ericaeous shrubs are not important factors to some of our heathland moths. Some species will feed on heathers (Erica and/or Calluna) whilst others will feed on the plants that grow amongst the heather matrix. National statuses of heathland moths Within the British list for the macro-moths, or larger moths, there are approximately 37 species which could be regarded as particularly associated with heathland. For these species heathland is at least a major, if not the only, habitat they occupy. These species are listed in the accompanying Table (see Table 1) , showing the national status for each, as per Waring (1994 & in press). The national status categories for macro-moths in Britain are defined as follows: Red Data Book (RDB) categories (for those species recorded from 15 or fewer 10km squares since 1980 or in rapid decline): RDB1 - Critically endangered - 50% chance of extinction in 10 years based on various criteria, particularly the rate of decline and perceived threats RDB2 - Endangered - 20% chance of extinction in 20 years, based on rate of decline and perceived threats RDB3 - Vulnerable - 10% chance of extinction in 100 years, based on rate of decline and perceived threats
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Speckled Footman Southern Chestnut Dingy Mocha Shoulder-striped Clover Ringed Carpet Bordered Grey Grass Eggar Purple-bordered Gold Horse Chestnut Bilberry Pug White-barred Clearwing Rosy Wave Broad-bordered Bee Hawk Silvery Arches Dotted Chestnut Grey Scalloped Bar Ling Pug Neglected Rustic Heath Rustic Dark Tussock Clouded Buff Wood Tiger Bird's Wing Broom-tip Emperor Oak Eggar Fox Moth True Lover's Knot Beautiful Yellow Underwing Common Heath Grass Emerald Narrow-winged Pug July Belle Black Rustic Streak Speckled Yellow Autumnal Rustic
Coscinia cribraria Agrochola haematidea Cyclophora pendularia Heliothis maritima Cleora cinctaria Selidosema brunnearia Lasiocampa trifolii ldaea muricata Pachycnemia hippocastanaria Chloroclystis debiliata Synanthedon spheciformis Scopula emutaria Hemaris fuciformis Polia trimaculosa Conistra rubiginea Dyscia fagaria Eupithecia goossensiata Xestia castanea Xestia agathina Dicallomera fascelina Diacrisia sannio Parasemia plantaginis Dypterygia scabriuscula Chesias rufata Pavonia pavonia Lasiocampa quercus Macrothylacia rubi Lycophotia porphyria Anarta myrtilli Ematurga atomaria Pseudoterpna pruinata atropuncta Eupithecia nanata angusta Scotopteryx luridata plumbaria Aporophyla nigra Chesias legatella Pseudopanthera macularia Paradiarsia glareosa glareosa
RDB1 RDB2 RDB3 RDB3 Na Na Na Notable/Nb Notable/Nb Notable/Nb Notable/Nb Notable/Nb Notable/Nb Notable/Nb Notable/Nb Local Local Local Local Local Local Local Local Local Common Common Common Common Common Common Common Common Common Common Common Common Common
Table 1. List of moths for which heathland is a principal habitat.
'Nationally scarce' species (formerly known as "Nationally notable") - for macro-moths there are two sub-categories: 'Nationally scarce' grade 'A' - recorded from 16-30 10km squares since 1980.
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'Nationally scarce' grade ' B ' , - recorded from 31-100 10km squares since 1980. 'Local' species are now formally defined as those recorded since 1980 from 101-300 of the 10km. squares in the national grid. 'Common' species are those occurring in more than 300 10km. squares. Note that 'Common' species are not necessarily numerous at individual sites, the category is based upon geographical distribution rather than abundance. Table 1 shows that 4 of the 37 identified heathland species are in the Red Data Book categories, 3 are nationally scarce category 'A,' 8 are nationally scarce category 'B,' 9 are local and 13 are common. One of the Red Data Book species, the Speckled Footman, Coscinia cribraria L., is literally confined to one or two sites in Britain now. The Moths The highly endangered Speckled Footman exists exclusively on heathland. It is a Red Data Book species which has become difficult to find in most of the sites where it was formerly known. It has always been confined to the heaths of Dorset and Hampshire. Previously it was not uncommon to record 40 or 50 in a night at these sites without difficulty. Recent records have been of one or two individuals at two localities, both in Dorset, in spite of many recorders combing likely areas both in Dorset and Hampshire. Its precise habitat requirements and larval foodplant(s) are not known but an old account (Fowler in South, 1961) mentions larvae basking on tussock grass Deschampsia cespitosa and the larva may favour hummocky areas for sun-bathing and feeding in spring. In 1996 a field meeting of the British Entomological and Natural History Society (BENHS) examined the New Forest heaths and bogs from Burley to Sway in search of the adult moth, in heathland habitats ranging from dry to wet and from short to mature heather. None was seen (Waring, 1997). Searches for the moth in Dorset are taking place in 1997 and 1998 with funding from the English Nature Species Recovery Programme but, at the time of going to press, no larvae have yet been found for study. Another species that occurs on heathland, the Clouded Buff, Diacrisia sannio L„ is becoming quite scarce in the lowlands of southern England. It needs a diverse flora and tends to be more frequent on the flower-rich heathlands. It is a species that has been very much lost from the Midlands and the northern parts of central England as small, isolated heaths have been developed. It is still fairly common on the restricted heaths of the Isle of Wight. Further north it starts to occur on moorland where it can become a fairly common insect. The catalogue of moths that are principally associated with heathland, but not exclusively so, include the Bordered Grey, Selidosema brunnearia Braud. The presence of this moth on heathland indicates an interesting and speciesrich habitat likely to produce others of the less widespread heathland insects. It is mainly to be found on the heaths of Dorset, Hampshire and Surrey, feeding on Bell Heather, Erica cinerea L., in the drier parts, but it is also capable of feeding on broad leaved herbs like Birds Foot Trefoil, Lotus corniculatus L. Occasionally it can be found on raised mosses. It also occurs on downland
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around Swanage and on sand hills on Hayling Island. The Grey Scalloped Bar, Dyscia fagaria Thunb., is a species which tends to be in the areas with shorter, more tussocky sward with areas of bare ground; the sort of places you could find the Grayling butterfly Hipparchia semele. The colouring of this moth blends in well with the kind of bleached ground that can be found in bare patches on heathland. The adult may also do a certain amount of basking because the males in particular are usually ready to take flight and are easily put up during the day. The larva of the Light Knot Grass, Acronicta menyanthidis Esper, feeds mainly on Bilberry, Vaccinium myrtillus L„ on heathland, but it will also feed on heathers, low sallow, Salix sp. and low birch, Betula sp. The moth is a northern species with the southward extent of it's British ränge occurring in East Anglia, at Roydon Heath in Norfolk. Although the moths of Britain have been studied for well over 200 years, new heathland species are still being discovered. The Southern Chestnut moth, Agrochola haematidea Duponchel, was discovered in 1990 (Haggett & Smith, 1993) on heathland in Sussex. Detailed observations were made at the Single site in Sussex, from which it appears that the species is quite specialised in its requirements, preferring the young shoots of mature Bell Heather. Subsequently, in the past two years the moth has been discovered in some of the New Forest heaths and within the last two weeks (i.e. October 1997) the BENHS has identified it as being distributed quite widely in the Forest. The Southern Chestnut may have escaped attention in the past because the adults emerge in October, but the mystery remains as to how the nineteenth Century entomologists failed to discover the distinctive caterpillars of the species when they were 'sweeping' for other larvae in the months of May and June. Could it therefore be an immigrant which is newly established in Britain, having recently colonised our heaths? The species certainly exists in the heathlands of Brittany and further south in France. The problem with this theory is that the species has never been recorded as a migrant by the army of entomologists who flock to the south coast with batteries of light traps at the times of the year when insect migration takes place. October is a particularly busy time for these migrations and the entomologists who study them. The case of the Southern Chestnut moth serves to emphasise that our understanding of the distribution and requirements of the moth fauna of heathlands is far from complete. The BENHS are holding another field meeting in October 1998 to search for the moth in additional parts of the New Forest heaths. Two species of moth which are likely to be found on most heathlands are the Beautiful Yellow Underwing, Anarta myrtilli, L. and the True Lover's Knot, Lycophotia porphyrea Denis & Schiff.. The larvae of both feed on heathers and the former seems to prefer the new growth. Both these moths also occur on moorland. The True Lover's Knot is a often an abundant moth and it sometimes wanders widely away from heathlands and turns up in light traps in inappropriate habitat, such as in woodlands far from any heather. Two species often found as larvae on heathland are the Fox moth Macrothylacia rubi and the Emperor moth Pavonia pavonia. Both larvae feed on the foliage of heathers but are also capable of feeding on a ränge of other plants and occur in various other habitats apart from heathland.
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A moth that is easily put to flight by those Walking through heathland is the Grass Emerald, Pseudoterpna pruinata atropunctaria Walker. This species feeds on gorse, Ulex sp. and is widely distributed. The Broad-bordered Bee Hawk-moth, Hemaris fuciformis L., is a moth found on heathland that is regarded more as a species that frequents woodland Clearings and sheltered areas where its larval foodplant, Honeysuckle, Lonicera periclymenum L., is to be found growing in sunny, warm conditions. On Dunwich Heath, for example, Honeysuckle can be found growing sprawled across the ground. Such heaths must provide nectar sources on or near them in late May and June for adult Bee Hawks to live long enough to mature and lay a fĂźll compliment of eggs. The Dingy Mocha, Cyclophora pendularia Cl. is a very localised heathland moth dependent on Sallows Salix spp. The adult is not unlike the much more widespread the Birch Mocha, Cyclophora albipunctata HĂźfn. whose larva feeds on Birches Betula spp.. Changes in nomenclature have contributed greatly to the confusion that exists in the historic records for these two species. In the past the scientific name pendularia was also applied to the Birch Mocha. The Dingy Mocha has probably only ever occurred on the heaths of Dorset and Hampshire, particularly in the Ringwood area and down into Dorset. The moth is a Red Data Book species and now appears on the UK Biodiversity Action Plan 'middle list'. The species is rapidly losing ground and is a priority for conservation. Sallows are often regarded as signs of scrub encroachment on heathland and are likely to be cleared, even in the name of conservation, so it is crucial that their importance for this species is recognised. The wider role of Sallows as a nectar source for heathland insects must also be mentioned and is discussed later. Management Issues Work is still being carried out to discover the position of each moth species in identified heathland continuums, from boggy to very dry heaths and from short to very deep swards.. It is quite clear that moths do specialise within these gradations, both in terms of the microclimates they need and the age and the parts of the foodplants on which they feed. Adults moths can have different requirements from their caterpillars, such as a need for nectar plants, and we should also bear in mind the needs of the pupal stage, which is often formed in the soil or occasionally spun up into the heathers themselves. The structure of the sward and the timing of any cutting or burning are influential in determining the moth species present and their abundance. It may be that the reported association of the Southern Chestnut with relatively mature stands of heather is an indication not that it prefers such plants but that it is intolerant of fire and slow to recolonise ground affected by fires. Small scale fires can be useful in returning the habitat back to an early successional stage, but large scale fires can be devastating. This is particularly a problem where heathland exists as small fragments separated from other heathland such that the potential for natural recolonisation by invertebrates is reduced. Frequent fires, like those caused by vandals in the degraded remains of heathland by housing developments, such as on the heaths of north
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Hampshire, can be very damaging indeed. Fire as a management tool is recommended only as a last resort. Moths have their predators and parasitoids which form part of often very complex food chains in which the moths can be a major component. In many of these instances it is the larvae of the abundant moth species that are involved. Sand Wasps, superfamily Sphecoidea, often inhabit heathland where the females sting larvae, carry them below ground in holes then lay an egg on their prey. The egg develops on the stunned larva and eventually produces another wasp. For the wasps it is critical that they are able to dig into the substrate easily. They prefer the sandier soils for this reason. Amongst heathland there are often little patches of subsidiary habitats which, when they are viewed en masse, wouldn't be classed as heath. These patches are very important. Ragwort, Senecio sp., for example, often grows on the edges of heaths, particularly where there are road verges. It can be a key nectar source in habitats that are otherwise in want of nectar. Bilberry Vaccinium myrtilli and Sallows Salix spp. are very good nectar sources in the spring and the larval foodplants of a number of localised moth species. Gorse provides nectar flowers for many weeks. Without such plants, heathlands can be very poor for nectar for the eleven months of the year when the heathers are not in flower. In these more complex, small-scale mosaics of plants there often are very species-rich invertebrate communities. Heathland is diverse and will develop on a wide ränge of substrates. Each type may have special moths and other invertebrates associated with it and needs conservation in its own right. For example, one of the Isle of Wight heaths is waterlogged clay for much of the year. It is very distinctive with Dyer's Greenweed, Cenista tinctoria Linn, and Sawwort, Serratula tinctoria Linn, growing amongst the heather. Sawwort is a plant of very great interest and the foodplant of the Reddish Buff moth, Acosmetia caliginosa Hübn. The moth is a highly endangered species now confined to this one native locality and is the subject of an English Nature Species Action Plan. The Reddish Buff formerly occurred in other sites on the Isle of Wight, in the New Forest and just outside the forest near Fareham in eastern Hampshire. It died out on the mainland in the early 1960s when its habitats became variously overgrown with native broadleaved trees or overshadowed by introduced conifers. It has recently been reintroduced to the mainland thanks to the English Nature Programme. The Kent Black Arches, Meganola albula Denis & Schiff., feeds on Dewberry, Rubus caesius L. which occurs on some of the warmer heaths and the moth also occurs on the same plant in other hot, dry situations. The occupied heaths are mainly near the south coast of England. It is very important that heathland management takes account of the significance of many of the woody shrubs that occur. Species like broom, gorse, sallow and birch are used by many species of heathland moths as larval foodplants as well as being nectar sources for the adults. Shrubs can become a problem when they become too frequent on heathland, but they are certainly essential elements to support a füll invertebrate fauna. Bare patches among heathland provide areas supporting microclimates with
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higher temperatures important for the development of many moths. A number of the caterpillars of moths that occur on heathland exploit warm periods, feeding and basking by day. These species, such as the Oak Eggar Lasiocampa quercus L. and the Fox inoth, are very hairy, which makes them unpalatable to most birds and enables them to be active by day. Most are black, or dark in colour. The dark coloration and für enable them to heat up, even in diffuse sun, and to attain temperatures of 30-37°C in ambients of 8 or 10°C. The Oak Eggar has genetically different 'races' which appear physically different in different parts of Britain. It is one of the species that extend into moorland. In the upland conditions of the north-west the moth takes two years to complete its life-cycle and in the south it only takes one. Those found on heathland in different parts of southern Britain have marked variability in appearance from heath to heath. It is possible to distinguish specimens from the New Forest, for instance, from those of the Suffolk heaths. In conserving the remaining fragments of heath, consideration must be given to the likelihood that other moths and other invertebrates may have developed local races. Concern is often expressed about erosion and public pressure on heathlands, in particular horse riding and use by 4-wheel drive vehicles, but it is important to put this issue into context. Heathlands have been 'blitzed' in the past and they are a product of use. In many parts of the country there was much more bare ground and loose substrates on heathland than there is today. This is evident from old photographs. Whilst over-use is a concern, naturalists should not become so 'precious' that heaths end up as 'wall to wall' heather with no bare ground. Also, bare ground on the flat is different in invertebrate terms from bare ground on the slopes, both situations having associated species. There are huge problems with heathland neglect, resulting in invasions of Birch, self-set exotic conifers and other species. When these trees and shrubs start to close ranks, heathland plants are lost and so too are the microclimates crucial for heathland invertebrates. The odd free-standing group of Birches and Sallows is valuable. It is important that certain elements are not eradicated from heathland. Stripping heather back almost to bare ground is a good way to produce the earliest successional stages provided that it is done on a small scale so that invertebrates can move in from nearby and exploit the re-growth. It may take 5 to 10 years to get the sward back again. If there are not seeding plants near to cleared areas, such as on heathland reclaimed from extensive conifer plantations, reintroduction of certain species like Sawwort may be necessary to speed up the process of colonisation. In-planting individual specimens of Sawwort has been successful in achieving local seeding as part of the Reddish Bff Recovery Project. The value to invertebrates of mature stands of tall heather and of senescent heather where very old and very young plants occur side by side in a small-scale mosaic should not be overlooked. Grazing is a key factor in maintaining heathland and it may have been responsible for creating it in the first place. The impact that various grazing animals have upon heathland is being studied. Horses, cattle, sheep and goats have different effects. Grazing in the winter is most sympathetic to invertebrates and intensive summer grazing should be avoided.
Management conclusions
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For invertebrates generally and moths in particular, the land manager needs to be given a clear image of what the habitat should look like in order to achieve each objective. This gives clear goals. Photographs, such as those presented in this lecture, are most helpful guides. •
Management of heathland must not lead to uniformity, as has happened over large parts of the New Forest. Regional differences should be recognised and small scale mosaics created within individual pieces of heathland.
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Frequent management, rather than elimination, is necessary to control woody plants.
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The plants that occur on heathland, apart from the heathers, are very important as both larval foodplants and as nectar foodplants.
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Bare patches of soil should be recognised as having microclimates and characteristics essential to many species of moths and other invertebrates.
•
The requirements of individual species and local races within species should be identified and considered in formulating management.
References Haggett, G. M. and Smith, C„ (1993). Agrochola haematidea Duponchel (Lepidoptera: Noctuidae, Cucullinae) new to Britain. Entomologist's Gazette 44: 183-203. South, R„ (1961). The moths ofthe British Isles. Series n. Warne, London. Waring, P., (1994). National Moth Conservation Project. News Bulletin 5. Butterfly Conservation, Dunstable. Waring, P., (1997). Field meeting report: Heathlands and bogs near Sway, New Forest, Hampshire, 27 July 1996. British Journal of Entomology and Natural History 10: 47-52. Waring, P., (in press). An atlas of the nationally scarce and threatened macro-moths of Great Britain. Joint Nature Conservation Committee. Peterborough. (Text prepared by Eric Parsons from notes by the Speaker and a recording made at the conference) Dr P. Waring 1366 Lincoln Road Werrington Peterborough PE4 6LS
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