The State Of Britain’s Larger Moths - Butterfly Conservation

45IntroductionRothamsted light trapThis report presents an overview of the statusof moths in Britain, drawing on important newresearch carried out by Rothamsted Researchand Butterfly Conservation, as well as manyother sources, including the ongoing work onconservation priorities under the UK BiodiversityAction Plan (BAP). With this information, andwidespread recording at the county level,Britain probably has the best-studiedmoth fauna in the world.The significance of mothsMoths are important. They represent one ofthe largest insect groups both in Britain andglobally, and thus make up a significant part ofour biodiversity. About 2500 species have beenrecorded in Britain so far, making moths over 30times more diverse than butterflies and five timesmore diverse than birds. Moths are traditionallydivided into larger (or macro) moths and smaller(or micro) moths, although this separation wasborn of convenience rather than scientific rationale.There are approximately 900 species of larger mothin Britain, and these are the main focus of this review.Moths are found in almost all habitats, from theshoreline to the mountain top, and occupy a widevariety of niches. In addition to feeding on theleaves, stems, flowers and seeds of terrestrialplants, there are British moths whose caterpillarsfeed on roots and wood, as well as on aquaticplants, lichens and algae, honeycomb, fungi, dung,fur and feathers, and even other caterpillars. Moths’reputation for eating clothes and other textiles isgreatly overstated. There are very few speciesamongst all this diversity that can cause suchdamage, and most of these are now very scarce.Moths are an important element of manyecosystems. Many other organisms depend uponmoths either for pollination1 or for food. Moths andtheir caterpillars are an important component of thediets of many birds. A few birds catch moths onthe wing, such as the Hobby, Little Owl, Nightjarand Spotted Flycatcher, but many collect mothcaterpillars to eat or feed to their young. Examplesinclude almost all the familiar garden species suchas Blue Tit and Great Tit, House Sparrow, Wren,Robin, Blackbird and Starling, as well as manybirds that have undergone severe declines,such as Grey Partridge, Stone Curlew,Bullfinch and Corn Bunting2.All 16 British species of bat (including threeUK BAP Priority Species) feed on moths to someextent, and moths make up a substantial part ofthe diet for Greater and Lesser Horseshoe Bats,Brandt’s, Bechstein’s and Leisler’s Bats, Noctule,Serotine and Barbastelle Bats, and Grey andBrown Long-eared Bats3. Many other smallmammals, including hedgehogs, wood miceand shrews, eat moth caterpillars and pupae.Moths and their immature stages are preyedupon by many other invertebrates and areunwilling hosts to numerous species of waspand fly parasitoids, fungi, bacteria and viruses.Blue Tit chicks alone are estimatedto eat 150,000,000,000,000 caterpillarsin Britain each year.Proctor et al. 1996Wilson et al. 19963Vaughan 1997Rothamsted ResearchThe study of mothsWe are fortunate in Britain to have a long andpopular tradition of recording and study of naturalhistory by amateur naturalists, dating back over300 years. Collecting moths and butterflies wasa social, even a fashionable, pursuit in the early1700s and many of the vernacular names still inuse today were coined at this time. By comparison,the current vernacular names of dragonflies dateonly from the 1980s.Moth recording is more popular today than ithas ever been. Although it is difficult to estimateprecise numbers, there are at least 2000 activemoth recorders in Britain at present, and almostcertainly many more4. However, there is no nationalrecording scheme covering all of the larger moths.The National Scarce Moth Recording Scheme hasoperated since 1991, collating records of onlythe threatened and scarce larger moths andthere are schemes for some groups of thesmaller (micro) moths4.The study of moths was revolutionised duringthe twentieth century by the invention of light traps.These traps, which are used by the vast majorityof moth recorders today, all utilise a light source toattract moths, which are then funnelled into a boxin which they settle, enabling them to be identifiedbefore release. Whilst, such traps have greatlyfacilitated the recording of moths, some speciesare rarely caught in light traps. Light traps alsodo not provide direct evidence of breeding status(unlike searching for caterpillars), as it is not alwayspossible to tell whether a captured moth has bredlocally or originated from much further away.Fox et al. 2005Woiwod and Harrington 19946For references see Conrad et al. 20041425The Rothamsted Light-trap networkRothamsted Research began a national networkof specially designed light traps in 19685. Sincethen, these standard traps have been operatedby volunteers at over 430 sites, with an averageof 83 traps running per year. The traps are runevery night at a wide range of sites and habitatsincluding private gardens, woodland, moorlandand on the coast.Rothamsted traps tend to catch small,representative numbers of moths, which makesthe samples effective and manageable withoutthreatening or affecting the moth populationsbeing studied6. For example, the average numberof Large Yellow Underwing Noctua pronuba,one of the most common larger moths in Britain,caught by Rothamsted traps since 1968 is just12 individuals per trap per year. This is a tinyand insignificant fraction of the overall population.Trends from this unique network of trapsare described later in this report.The Rothamsted light-trap network hasgenerated one of the longest-runningand geographically extensive data sets oninsect populations anywhere in the world.

67The changing moth fauna of BritainThe number of moth species living in Britain ischanging all the time as resident species becomeextinct and new ones colonise our islands fromcontinental Europe or further afield. The mostrecent summary of these changes to the residentmoth fauna during the twentieth century, concludedthat 62 resident moth species are now consideredextinct in Britain and 89 species have colonisedsuccessfully7. Many of these new colonisers feedon non-native plants in our gardens and parks7, 8.Several other species may be extinct, having notbeen seen for a number of years (e.g. the OrangeUpperwing Jodia croceago). Since 2000, over25 moth species have been recorded as new toBritain and several of these are now breeding(e.g. Ectoedemia heringella and the Horse ChestnutLeaf-miner Cameraria ohridella). South-east Englandhas borne the brunt of more extinctions andreceived more colonisations than any other region7.There is a clear national pattern of moth speciesrichness, with more species recorded in southerncounties than in the north. Dorset has the highesttotal of larger moths (687 species by 2001) andShetland the lowest (146 species)9. Of course,some species only occur in the north and othersonly in the south.The decline of moths at the local level is highlightedin many county moth books, which include longlists of locally extinct and declining species. Forexample, in Cornwall 135 moth species are listedas not recorded since 190610, 112 species havebeen judged likely to be extinct in Hertfordshire11,and in Herefordshire and Worcestershire 104are deemed to be extinct in both counties withmany more declining12.Parsons 2003Agassiz 19969Leverton 2001Smith 1997Plant 200412Harper and Simpson 2004710811Lesser Belle Colobochyla salicalisand Viper’s Bugloss Hadena irregularisbecame extinct in Britain duringthe twentieth century D.GreenLight Brown Apple Moth Epiphyas postvittanaP.PughAustralian invaderThe Light Brown Apple MothEpiphyas postvittana, a smaller moth native toAustralia, was first recorded breeding in the wild inBritain in Cornwall in 1936. Initially its spread wasslow, taking almost 20 years to reach Devon, butsince the 1980s it has expanded rapidly and is nowrecorded widely across England and Wales, mainlyin gardens, and has been reported in Ireland. It hasnot been recorded in continental Europe, yet!Declines from the Rothamsted networkPerhaps the most convincing evidence ofwidespread moth declines comes from the analysisof 35 years of data from the Rothamsted light-trapnetwork in Britain. This shows that between 1968and 2002 the total number of larger moths haddecreased by almost one third (Figure 1).Figure 1 Total larger moth catches in the Rothamsted light-trapnetwork 1968-200213. The total number of moths recorded hasdecreased by 32%.The TRIM index provides a good estimate of relativechange in moth abundance (see Conrad et al. 2004for more information on TRIM)13The spread of the Light Brown Apple Moth1936 CornwallFirst confirmed breeding in the wildby 1955 Devonby 1970 Essex, Hampshireby 1980 Kent, Oxfordshireby 1990 Dorset, Gloucestershire, Middlesex,Leicestershire, Somerset, Sussex,Wiltshire.First record in Wales (Glamorgan)by 1995 Much of southern England,had reached North Wales,Lancashire and Yorkshireby 2000 Continued expansion in the Midlandsand North Wales, and had reachedSuffolk and Cumbria.First record for Ireland (Co. Wexford)2001 First record in Scotland (Dundee)2002 Isle of Man, Merionethshire, Midlothian2003 Co. Wicklow.First record for Northern Ireland(Co. Antrim)References:Porter 2001, Bland 2002, Langmaid and Young 2003, 2004.

89Trends of rare mothsFigure 2Declining distribution of theBrighton Wainscot Oria musculosa.Figure 3Declining distribution of thePale Shining Brown Polia bombycina.Maps produced from the National Scarce Moth Recording Scheme databaseIn addition to the 62 moth species consideredto have become extinct in Britain during thetwentieth century, the National Scarce MothRecording Scheme14, shows that many speciesare now nationally threatened or scarce.Moths and the UK Biodiversity Action PlanFollowing the 1992 Earth Summit in Rio, the UKBiodiversity Action Plan (BAP) was developed tofocus Government action to conserve species andhabitats. Currently, 53 moths are afforded the toppriority status under the UK BAP. These PrioritySpecies comprise 52 larger moths and a singlesmaller moth (the Basil Thyme Case-bearerColeophora tricolor). Butterfly Conservation takesthe lead role in co-ordinating action on all but one(the New Forest Burnet Zygaena viciae) of thesespecies, sometimes in collaboration with otherorganisations. Actions typically involve surveyand monitoring work, ecological research,habitat management and safeguarding colonies,as well as promoting moth conservation tolandowners, councils, wildlife organisationsand the general public.The progress made towards achieving the targetsset out in the 53 action plans for UK BAP mothshas been reviewed recently15. The discovery ofnew colonies, ecological research and habitatmanagement have helped the situation of 27priority moths since the UK BAP was published,but the fortunes of eight species have worsenedconsiderably. 15 are considered to have no overallchange (although in three cases this is because thespecies are thought to be extinct!) and there isinsufficient information for the remaining three tomake a sound judgement (the Barred Tooth-stripedTrichopteryx polycommata, Northern Dart Xestiaalpicola and Sword-grass Xylena exsoleta).A recording scheme run by Butterfly Conservation in associationwith the Joint Nature Conservation Committee, collating recordsof all Red Data Book and Nationally Scarce larger moths14All of the UK BAP priority moths have undergonesubstantial declines in the past and eight specieshave continued to decline. Examples include theBrighton Wainscot Oria musculosa (Figure 2),which is associated with cereal fields, and PaleShining Brown Polia bombycina (Figure 3), bothof which occur on and around Salisbury Plain.No Brighton Wainscot have been reported inBritain since 2001, prompting concerns thatthe species may now be extinct, but habitatmanagement undertaken for it may have benefitedother species such as the Pale Shining Brown,Corn Bunting and rare arable weeds. The MarshMoth Athetis pallustris appears to have becomeextinct at several former sites and is now knownfrom only two sites (in Lincolnshire). In addition,a further UK BAP species, the Orange Upperwingmay be extinct now, as there have been noconfirmed British records since 1994, despiteconsiderable survey effort.Under the auspices of the UK BAP, and theregional and local biodiversity action plans thathave developed more recently, great improvementshave been made in understanding the statusof the priority moth species and some notableconservation successes achieved. However, muchmore work and far more resources are requiredto fully implement the existing action plans forpriority moths. Many additional scarce speciesmeet the criteria for inclusion in the UK BAP, asdo many ‘common’ species found to be in rapiddecline in the analysis of Rothamsted networkdata. Therefore, the number of priority mothsmay increase after the BAP review in 2006.Additional resources to maintain the successand the credibility of the BAP process mustaccompany such an increase.15Parsons 2004l 1999-2003l 1980-1998pre 1980Research conducted on the Fiery ClearwingPyropteron chrysidiformis has led to amuch better understanding of its ecologicalrequirements. As a result, managementrecommendations can now be given tolandowners and new habitat has beencreated in Kent for this very rare moth.R.ThompsonNew colonies of the very rare moth Dark BorderedBeauty Epione vespertaria have been located inScotland and habitat management is underway.However, the species remains a high conservationpriority, as it is only known from four sites in the wholeof Britain (in Scotland and northern England). R.Levertonl 1999-2003l 1980-1998pre 1980The New Forest Burnet Zygaena viciaesurvives at a single British site, in westernScotland. The population has respondedpositively to conservation action (protectionfrom sheep grazing), with adult mothnumbers increasing from only 20 individualsin 1990 to over 8,500 in 2003. R.LevertonReference: Young and Barbour 2004.Thanks to new surveys by volunteers andButterfly Conservation staff, the knowndistribution of the Buttoned SnoutHypena rostralis has almost tripled fromonly c.65 10km squares prior to the UKBAP to around 180 10km squares. P.Pugh

1011Populations of these species have declined 1968-2002.Iron Prominent Notodonta dromedarius (top) by 34%,Birch Mocha Cyclophora albipunctata (below right) by 51% andClouded Buff Diacrisia sannio (below left) by 64% R.Thompson40VulnerableNumber of species50Endangered60302010 e change over 10 yearsFigure 4 Frequency distributions of population change of 337British moth species. The size of population change is thepercentage change over a 10 year period, calculated from theannual rate of change estimated from long-term trends from1968-2002. The blue vertical line shows the median 10 yearchange. X-axis labels are the upper limits of each class.Shaded areas correspond with the IUCN criteria thresholdsfor the Endangered and Vulnerable status.Trends of common mothsAnalysis of the Rothamsted dataIn 2003, Butterfly Conservation and RothamstedResearch launched a collaborative project toassess population trends in individual moth speciesfrom the light-trap data set. The Esmée FairbairnFoundation provided funding for the project.Long-term (35 year) trends were obtained for337 common, larger moths based on annualindices of abundance calculated using theTRIM modelling procedure16. In this context,'common' relates to species with sufficientcaptures for the calculation of national trends.Some of these 'common' species may beabsent or scarce in parts of Britain.Common moths in declineu Most species are declining, some atvery alarming rates (Figure 4). Two thirds(226 species) show a decreasing populationtrend and one third (111 species) show anincrease in population over the 35 year study.Twice as many common larger mothspecies have declined as increased overthe past three decadesu 75 species decreased by over 70% between1968 and 2002 (listed in Table 1 on p.14).u Another 57 species decreased by over 50% anda further 60 species decreased by over 25%.As a result of these declines, many commonmoths now meet the selection criteria forthe UK Biodiversity Action Plan 2006 review(see Table 1 on p.14). Butterfly Conservation hasput most of these species forward for considerationas Priority Species for conservation action.Conrad et al. 2004IUCN 200118Conrad et al. in prep.1617New Red Data Book speciesThe Red Data Book criteria developed by IUCN (theWorld Conservation Union) are used around the worldto determine the conservation priority level of species17.If the IUCN criteria are applied to the nationalpopulation trends generated from the Rothamsteddata, 71 common British moths would be consideredthreatened (see Table 1 on p.14). 15 species wouldqualify as Endangered and 56 as Vulnerable18. None ofthese have been listed as Red Data Book species beforein Britain and none were previously thought to warrantany conservation priority in the UK BAP. Although thereare considerable annual fluctuations in the abundanceof many species, the trends show a steady declinethrough the 1970s, 80s and 90s.These findings are extremely alarming. Few naturalistswould have noticed or predicted the dramatic declinesof many of these larger moths, with the possibleexception of species such as the V-moth Macariawauaria and Spinach Eulithis mellinata (see p.25).Moth recorders, conservationists and the public willprobably be surprised and shocked that so manycommon species have declined to such a greatextent in recent decades. There are obvious parallelswith the dramatic and well-publicised declines ofcommon birds such as the Skylark, House Sparrowand Starling, although none of these species havedeclined by as much as the 75 larger moths in Table 1.It is well known that there are many threatened andscarce species in Britain, but this is the clearest signalyet that our common species, which underpin the foodchains and ecosystems that maintain our biodiversity,are also undergoing catastrophic change.71 common British moths (21% of the speciesassessed in this research) now qualify asEndangered or Vulnerable as a result of rapiddeclines over recent decades

1213Severlely declining common moths (1968-2002).Autumnal Rustic Eugnorisma glareosa 92% declineGhost Moth Hepialus humuli 73% decline R.LevertonBlood-vein Timandra comae 79% decline R.ThompsonENDANGERED:The Dusky ThornEnnomos fuscantaria showsthe greatest decline of all 337larger moth species analysed.It has decreased by 98% overthe 35 year study. This distinctivegeometrid moth is readilyattracted to light traps and fliesduring the late summer andautumn. Its distribution isdescribed as “.occurs, notuncommonly, throughout Englandand Wales”19 and “Common.Fairly generally distributed andoften frequent in England andWales”20. Despite the abundanceof the main caterpillar foodplant,ash, the moth has undergonean extraordinary andunexplained decline.P.Pugh1920Skinner 1998Waring and Townsend 2003ENDANGERED:The Figure of EightDiloba caeruleocephalais a woodland, hedgerowand garden moth describedas “Common. Well distributedthroughout most of England,Wales and southern Scotland”20.It has declined by 95% over 35years and qualifies as a RedData Book Endangered species.This moth was caught in over30% of Rothamsted traps inthe early years of this study,but had declined to onlyaround 10% during the finalyears of the twentieth century.R.ThompsonVULNERABLE:The CinnabarTyria jacobaeae is one of themost familiar larger moths onaccount of its attractive blackand red wings and because ofits distinctive orange and blackbanded caterpillars found onragwort. It is widespread andcommon in southern Britain,becoming more local and coastalin Scotland. Between a third andhalf of Rothamsted traps catchthis species and this proportionhas not changed much duringthe study period. However, itspopulations have suffered along-term decrease of 83%over 35 years, marking thespecies Vulnerable accordingto IUCN criteria.D.GreenR.LevertonLackey Malacosoma neustria 90% decline P.PughOak Hook-tip Watsonalla binaria 81% decline R.LevertonWhite Ermine Spilosoma lubricipeda 77% decline R.Thompson

1415Table 1 Larger moth species that have declined by –70%over 35 years and their IUCN Red List categories.# Identifications confirmed by examination of internal anatomy† Selection of candidate species for UK BAP Priority status is made on the basis of a 50% decline over 25 years* The IUCN classifications are based on 10 year population trends of the larger British moths estimated from the Rothamsted data.The 10 year moth population trends were calculated from the annual rate of decline across the whole 35 year study period (i.e. they are notthe trends from the most recent 10 years). When, as in this case, the causes of trends are not understood or the declines are likely to beongoing, IUCN criteria define species with 10 year decreases of 50% or greater as Endangered and those with 30% or greater as Vulnerable.% change % changeoverover35 years25 years† IUCN category*SpeciesDusky ThornHedge RusticV-mothDouble DartGarden DartGrass RivuletDark SpinachSpinachFigure of EightAnomalousDusky-lemon SallowAutumnal RusticWhite-line DartDark-barred Twin-spot CarpetSeptember ThornEnnomos fuscantariaTholera cespitisMacaria wauariaGraphiphora augurEuxoa nigricansPerizoma albulataPelurga comitataEulithis mellinataDiloba caeruleocephalaStilbia anomalaXanthia gilvagoEugnorisma glareosaEuxoa triticiXanthorhoe ferrugataEnnomos athered GothicBeaded ChestnutDeep-brown DartLackeyBrindled OchreGarden TigerHaworth’s MinorDot MothLarge NutmegFlounced ChestnutLatticed HeathPretty Chalk CarpetLarge WainscotPale EggarRosy RusticSmall Square-spotHeath RusticBroom-tipOblique CarpetCinnabarSprawlerSmall EmeraldTholera decimalisAgrochola lychnidisAporophyla lutulentaMalacosoma neustriaDasypolia templiArctia cajaCelaena haworthiiMelanchra persicariaeApamea ancepsAgrochola helvolaChiasmia clathrataMelanthia procellataRhizedra lutosaTrichiura crataegiHydraecia micaceaDiarsia rubiXestia agathinaChesias rufataOrthonama vittataTyria jacobaeaeAsteroscopus sphinxHemistola erableVulnerableSpeciesSallowCrescentOak LutestringNeglected RusticOak Hook-tipAugust ThornRosy MinorBrindled BeautyRed CarpetKnot GrassGrey Mountain CarpetGreen-brindled CrescentBlood-veinDark BrocadeThe StreakSmall PhoenixGrey Dagger#Broom MothWhite ErmineMullein WaveGalium CarpetPowdered QuakerDusky BrocadeBrown-spot PinionRusticCentre-barred SallowMouse MothMottled RusticShaded Broad-barBuff ErmineMinor Shoulder-knotGhost MothShoulder-striped WainscotEar Moth#July Belle/Lead BelleLight ArchesBuff ArchesDark Umber% change % changeoverover35 years25 years† IUCN category*Xanthia icteritiaCelaena le

plans for priority moths. Additionally, many . Robin, Blackbird and Starling, as well as many birds that have undergone severe declines, such as Grey Partridge, Stone Curlew, . 12 individuals per trap per year. This is a tiny and insignificant fraction of the overall population.