Habitat loss, degradation and fragmentation
The destruction and modification of habitats by human activity is regarded as the foremost cause of global biodiversity loss (Diamond et al., 1989; Brooks et al., 2002; Dirzo & Raven, 2003; Fahrig, 2003). Habitat loss (including deterioration in quality and the isolation effects of fragmentation) has also been identified as the principle driver of butterfly declines in Europe (e.g. Asher et al., 2001; Maes & Van Dyck, 2001; Warren et al., 2001; Wenzel et al., 2006; Bulman et al., 2007; Hanski & Pöyry, 2007; Van Dyck et al., 2009; Öckinger et al., 2010). Consequently, it seems probable that habitat loss will have influenced moth abundance and distributions in Britain (Fox et al., 2006b), although habitat degradation patterns vary geographically and, therefore, impacts on species are expected to differ between areas. It is possible that the better performance, on average, of moth populations in northern Britain stems from lower levels of habitat degradation relative to the southern half of Britain, although a climatic explanation, or a combination of both, is also plausible (see section Climate change).
There is little direct evidence for habitat loss, degradation or fragmentation effects on moth populations in Britain (or elsewhere). However, as for butterflies, there is considerable circumstantial evidence that the widespread destruction of semi-natural habitats has had a severe impact on specialist moths, and it has been implicated in the extinction of species, including Laelia coenosa reed tussock and Lymantria dispar gypsy moth because of wetland drainage, and Emmelia trabealis spotted sulphur as a result of afforestation and agricultural intensification (Majerus, 2002). Habitat changes may also have played a role in the declines of species such as Pyrausta sanguinalis in sand dunes, Aspitates gilvaria straw belle and Siona lineata black-veined moth on unimproved grassland, Heliothis maritima shoulder-striped clover and Coscinia cribraria speckled footman on lowland heath and Pareulype berberata barberry carpet in hedgerows (Fox et al., 2010).
Fragmentation effects have been detected in few empirical studies of moths (Öckinger et al., 2010), but generally biodiversity impacts from fragmentation per se tend to be relatively small compared to the effects of habitat loss and habitat quality (Thomas et al., 2001; Fahrig, 2003; Hodgson et al., 2009). In addition, theory predicts that mobile species are less likely to experience negative effects of isolation. Mobility is poorly understood in most moth species (apart from long-distance migrants, e.g. Chapman et al., 2011), but recent evidence suggests that many species are relatively mobile (Franzén & Nilsson, 2007; Merckx et al., 2009a, 2010a,b; Betzholtz & Franzén, 2011; E.M. Slade, T. Merckx, T. Riutta, D. Redhead, D. Bebber, P. Riordan & D.W. Macdonald, unpubl. data; but see Nieminen, 1996; Nieminen et al., 1999). Thus, while fragmentation might be expected to be important for some specialised species with low to intermediate mobility (Thomas, 2000), it is unlikely to be a principle driver of the declines of many widespread moths in Britain and elsewhere.
In contrast, it seems highly plausible that the widespread destruction of semi-natural habitats that took place across Britain during the twentieth century had substantial impacts on moths. These were rarely documented through site-based population monitoring at the time (although see Woiwod & Gould, 2008), and land-use change effects cannot easily be assessed retrospectively. However, recent research has started to shed light on the impacts of land use on moth populations, by contrasting different levels of management intensity.
Agricultural management. Agriculture is a dominant and socioeconomically important land use in Britain and much of Europe and is also of great importance for biodiversity (Bignal & McCracken, 1996; Halada et al., 2011). However, agricultural intensification generally reduces habitat area, quality and heterogeneity through the interlinked impacts of increased agrochemical use, changes in tillage/grazing practices and larger cropped areas and is widely recognised as a major driver of biodiversity decline (Donald et al., 2001; Benton et al., 2002, 2003; Robinson & Sutherland, 2002; Kleijn et al., 2009). The substantial drop in moth abundance and diversity recorded on farmland at Rothamsted between the 1940s and 1960s was concomitant with agricultural intensification of the surrounding land (Woiwod & Gould, 2008). Specific changes included a move from grassland to arable cultivation, removal of hedgerows and uncultivated areas to increase field size and built development. A number of other recent studies have also implicated aspects of intensification with reduced moth populations (see below).
Taylor and Morecroft (2009) reported significant increases in moth abundance and species richness on a farm in southern England, following organic conversion and simultaneous entry into an agri-environment scheme (AES) and the adoption of less-intensive farming techniques. Wickramasinghe et al. (2004) found significantly higher species richness and diversity of moths on organic farms than on conventional ones in a study of 24 pairs of (livestock and mixed) farms in Britain. The authors ascribed this difference to the reduced use of agrochemicals, but many other factors could also be responsible. Pocock and Jennings (2008) conducted a similar study, but were able to separate out several different elements of intensification. They found the greatest effects on moth abundance related to the presence or absence of field boundaries (moths benefited from boundaries), both in arable and in pasture fields, with relatively little impact from either agrochemical inputs or the switch from hay to silage cropping regimes. This corroborates findings that the area of hedges and bushes in the local environment around RIS traps on the Rothamsted Estate was an important predictor of moth abundance and diversity (Woiwod & Gould, 2008).
Work by Merckx et al. (2009a,b, 2010a,b) also highlighted the importance of field boundaries for moths in agricultural settings. The presence of hedgerow trees and 6-m-wide grassy field margins were both significantly correlated with increased moth abundance and diversity (Merckx et al., 2009b). Such field margins, but not hedgerow trees, were management options for which ‘entry level’ AES payments were available at the time of the studies. Hedgerow trees had the greater effect, but only when targeted management advice resulted in elevated levels of AES uptake in the surrounding landscape (Merckx et al., 2009b). Hedgerow trees had a positive impact on a wide range of moths, not just those species that utilise them as larval hostplants, possibly because they provide sheltered micro-climates in relatively exposed landscapes (Merckx et al., 2010a).
Another study (Fuentes-Montemayor et al., 2011) found benefits for moths from AES management at farms in Scotland. Conversion of conventional arable or improved pasture fields to more species-rich grassland under AES resulted in increased abundance and species richness of moths. Other AES options, including the creation of extensively managed margins, also led to increased moth numbers and abundance, but no effects were found for AES hedgerow management.
Agricultural use of chemicals, both fertilisers and pesticides, increased enormously as an integral part of agricultural intensification during the latter half of the twentieth century. With direct and indirect (e.g. via impacts on larval hostplants, nectar sources, vegetation structure and composition) effects on many taxa both within cropped areas and on field margins (Freemark & Boutin, 1995; McLaughlin & Mineau, 1995; Longley & Sotherton, 1997), these agrochemicals may have played a prominent role in the decline of moths in Britain. However, disentangling the relative contributions of fertilisers or pesticides from other elements of agricultural intensification at a landscape or national scale is problematic (Benton et al., 2003; although see Gibbs et al., 2009).
Ongoing agricultural development will alter the patterns of agrochemical use and the nature of the substances deployed. Such changes may increase or decrease potential impacts on biodiversity and should be evaluated prior to introduction. For example, genetically modified herbicide-tolerant crops alter pesticide regimes and aim to improve the efficacy of weed control, with potential impacts on plants and associated invertebrates both within the crop and on field margins (Roy et al., 2003). Novel crops (e.g. biofuel and biomass), increasing resistance to pesticides and changing food security conditions may drive increased intensification and additional exposure to existing and future agrochemicals (Sutherland et al., 2008).
Often, subtle aspects of habitat quality are vital for population persistence. Change in the grazing intensity of agricultural land is known to alter habitat quality critically for many taxa, including butterflies, vascular plants and some specialist moth species. For example, increased intensity of livestock grazing almost led to the extinction of Zygaena viciae New Forest burnet from Britain (Young & Barbour, 2004). Experimental reduction in the high intensity of livestock grazing typical of commercial upland agriculture led to significant increases in moth abundance and species richness (Littlewood, 2008). While less-intensive grazing may benefit grassland insects, the permanent abandonment of traditional pastoral agriculture, leading to rapid ecological succession, can be detrimental (Balmer & Erhardt, 2000; Bourn & Thomas, 2002; Öckinger et al., 2006; van Swaay et al., 2006; Settele et al., 2009; Stefanescu et al., 2009). Such abandonment is thought to have contributed to declines of moth species in Britain such as Adscita statices forester and Hemaris tityus narrow-bordered bee hawk-moth (M. Parsons, pers. comm.).
Woodland management. Native broad-leaved and coniferous woodlands are important habitats for a wide range of taxa in Britain, including a high proportion of the macro-moth species. Although woodlands of high biodiversity value have been destroyed, the net amount of broad-leaved woodland has increased in Britain over recent decades, in stark contrast to the amount of other semi-natural habitats. And yet, the changing status of key monitored taxa, such as birds, butterflies and plants, clearly indicates a decrease in woodland biodiversity (Fuller et al., 2005; van Swaay et al., 2006; Carey et al., 2008; Fox et al., 2011a). A range of factors are responsible for these declines but, for butterflies, the main causes appear to be altered structural diversity, botanical communities and micro-climatic conditions associated with a shift towards high-forest management (including the cessation of traditional practices such as coppicing), leading to increasing shade and fewer open, early-successional habitats (Warren & Key, 1991; Sparks et al., 1996; Asher et al., 2001; van Swaay et al., 2006; Clarke et al., 2011). Conrad et al. (2004) found that moth species utilising deciduous trees as larval hostplants tended to have negative population trends in Britain, while the few species (such as Thera britannica spruce carpet and Panolis flammea pine beauty) that exploit coniferous trees generally increased. The latter is hardly surprising, given the massive expansion of conifer plantations (a 20-fold increase, 1800–1980) in Britain.
Moth species assemblages vary between woodland types and along geographical gradients, but also within woods (e.g. species associated with mature trees, others with edge habitats or open, grassland conditions in rides and glades) and even between age-classes of managed areas such as coppice coupes (Broome et al., 2011).
T. Merckx, R. E. Feber, D. Hoare, M. S. Parsons, C. Kelly, N. A. D. Bourn & D. W. Macdonald (unpubl. data) assessed the macro-moth response to standard woodland conservation management practices in a landscape-scale study in southern England. They found that moth abundance increased with the amount of shelter: open, recently coppiced areas had the lowest abundance and standard (narrow) forest rides and blocks of mature woodland had the highest. However, common management techniques to open up woodland for the benefit of taxa such as butterflies, including coppicing and ride widening, did benefit the overall species richness of moths in the woodland landscape. Wide rides, although containing relatively low abundance levels of moths, were as rich in species as the standard rides and mature woodland. Moreover, the introduction of increased structural and micro-climatic heterogeneity increased overall species richness by providing niches for moths that were not found elsewhere in the woods. The authors caution, however, against opening up the sheltered late-successional cores of woodlands as these support high abundance and species richness of many specialist and conservation priority moths that are not found in more open habitats.
Most woodland specialist moths may have benefited from the switch to high-forest management in broad-leaved woodland habitats over recent decades, although they will have been impacted detrimentally by conversion to coniferous forestry. However, it is equally clear that many moths, mostly generalist species of more open habitats (but also some specialists such as Anania funebris and Minoa murinata drab looper) will have undergone substantial decreases in abundance and distribution as a result of changing woodland management.
Urbanisation. The impacts of urbanisation on biodiversity are complex. Increasing urban land cover typically replaces and fragments semi-natural habitat, leading to decreases in biodiversity, particularly among specialist species (Bergerot et al., 2010; Gaston & Evans, 2010; UK National Ecosystem Assessment, 2011). However, urbanisation can also cause increases in biodiversity among particular taxa (McKinney, 2008). In addition to habitat loss, urbanisation also generates other environmental changes that might alter biodiversity including local climatic effects, chemical, light and sound pollution and the introduction of non-native species. Thus, urbanisation impacts on moths need also to be considered in the context of the effects of climate, pollution and non-native species (see below).
Although reduced levels of moth abundance and diversity have long been associated with urbanisation (Taylor et al., 1978), there do not appear to have been any published studies of the specific impacts of urbanisation on the moth fauna of Britain, nor of the relative value for moths of habitat fragments in urban surroundings compared with other degraded land uses such as intensive agriculture. In California, Rickman and Connor (2003) found no consistent differences between leaf-mining moth communities of remnant habitats in urban vs. agricultural settings.
Urban greenspace, including private gardens, supports diverse moth communities. As with agriculture, intensive management of gardens and parks (including pesticide use) is expected to reduce moth numbers, although quantitative studies are lacking. Recent trends for reduction in garden size, both in new-build developments and through in-fill (building new housing in existing gardens), and loss of vegetated area to hard surfaces (e.g. driveways, parking, patios, decking) and garden buildings (e.g. sheds, greenhouses) (Loram et al., 2008; Smith, 2010; UK National Ecosystem Assessment, 2011) will have reduced resources available to moths, but no population-level studies have been conducted.
In contrast, increased public awareness of biodiversity and interest in ‘wildlife gardening’ may have improved habitat quality in some gardens and parks, and the cultivation of non-native plants has provided opportunities for a few native and newly colonising moth species (see section Non-native species).
Habitat loss summary. Direct evidence of the impact of historical habitat loss, decreasing quality or fragmentation on moth abundance or diversity is largely lacking. However, the weight of contemporary evidence suggests that reducing the intensity of agricultural management (including at field boundaries) and reinstigating traditional management to recently neglected broadleaved woodlands increase moth abundance and diversity at the landscape scale. The implication is that the predominant trends in land-use management in twentieth-century Britain and concomitant loss of breeding habitat must have resulted in considerable declines for many moth species.
Eutrophication (increased soil and water fertility caused by unintended nutrient inputs from fossil fuel combustion and agriculture) is altering the plant composition and vegetation structure of many habitats, often in conjunction with other drivers such as management intensity and climate change (Bobbink et al., 1998; Van der Wal et al., 2003; Hartley & Mitchell, 2005). Biodiversity of plant and insect populations (e.g. butterflies) correlates negatively with nitrogen input (Pollard et al., 1998; Stevens et al., 2004; Öckinger et al., 2006; WallisDeVries & van Swaay, 2006), so there may be substantial, unquantified impacts on moth populations resulting from such chemical pollution.
Links between other forms of chemical pollution and moth populations appear completely unstudied in Britain. It has been suggested that the population increases seen among moths that utilise lichens and algae as larval hostplants (e.g. the footman moths in sub-family Lithosiinae) might be linked to the recovery of some of these organisms following amelioration of sulphur dioxide pollution (Fox et al., 2006b). However, there is no direct evidence for such causality. Similarly, while there has been much research into the impacts of pollution by heavy metals and other chemicals on humans, other vertebrates and plants (e.g. Sharma & Agrawal, 2005), there have been few studies involving moths. Negative fitness impacts of chemical pollution on moth larvae have been shown in Europe (Mitterböck & Fuhrer, 1988; van Ooik et al., 2007; van Ooik & Rantala, 2010), but population effects have not been established.
In summary, there is no evidence currently available to suggest that chemical pollution in its many, complex and interacting forms is a driver of change in moth populations in Britain. However, as a key constituent of agricultural intensification and through negative effects on the insects themselves, larval hostplants and other essential resources, it is probable that chemical inputs in the form of herbicides, insecticides and fertilisers have contributed to the decline of Britain’s moth populations.
Many moth species are attracted to artificial light, although the mechanistic basis for this behaviour is not entirely clear (Young, 1997). Artificial light elicits a wide range of responses in many animal and plant species, but there is insufficient knowledge about impacts in the wild, especially among invertebrates (Longcore & Rich, 2004; Rich & Longcore, 2006; Sutherland et al., 2006; Poot et al., 2008; Royal Commission on Environmental Pollution, 2009; Stone et al., 2009; Bruce-White & Shardlow, 2011).
Outdoor lighting can cause direct mortality, increase exposure to predators and have disruptive effects on various elements of moth behaviour and life cycles (Frank, 2006; Bruce-White & Shardlow, 2011). However, such effects vary between species, populations and even individuals, as well as with the spectral composition of the light sources. Furthermore, direct impacts of light pollution must be quantified separately from the other effects of urbanisation and habitat loss that usually accompany an increase in lighting levels.
Unfortunately, despite a massive increase in background light levels in Britain and many other parts of the globe, there have been few studies on the impact of outdoor lighting on moths (e.g. Eisenbeis, 2006; van Langevelde et al., 2011) and none that have assessed population-level or community-level effects.
Conrad et al. (2006) undertook a comparison of moth population trends from the RIS network using satellite data on the change in background illumination levels in Britain. There was no significant difference between total moth abundance in areas exposed to increased background light levels and those unaffected. However, illumination data were available for only a short period (1992–2000), and therefore this finding does not preclude light pollution as a driver of long-term moth declines in Britain.
In summary, although the attraction of moths to artificial light has been known for centuries and disruptive and fitness-reducing impacts of such attraction have been demonstrated, light pollution remains uninvestigated as a possible cause of population-level changes in moths.
Climate change has already caused considerable modification of geographical range, abundance and phenology for many species globally (Parmesan & Yohe, 2003; Gregory et al., 2009; Thackeray et al., 2010; Chen et al., 2011) and is perceived to be a major threat to biodiversity (Thomas et al., 2004a, 2006; Pounds et al., 2006; Ohlemüller et al., 2008; Bálint et al., 2011; Maclean & Wilson, 2011).
In Britain (and elsewhere in north-west Europe), moderate levels of climate warming may bring opportunities for thermally constrained species such as insects and there is strong evidence, for example, that some butterflies have already expanded their ranges and flight periods in response to climate change (Roy & Sparks, 2000; Warren et al., 2001; Hill et al., 2002; Davies et al., 2006; Menéndez et al., 2007). At the same time, climate change may threaten other species through the loss of thermally suitable habitat space (Franco et al., 2006; Wilson et al., 2007; Maes et al., 2010), altered phenological synchrony with hostplants (Singer & Parmesan, 2010) and even hybridisation (Mallet et al., 2011).
Established links between climate change and the decline of moths in Britain are limited at present. Population trends of a small group of northerly distributed species (i.e. those with a southern range margin within Britain) decreased compared with southerly distributed moths (Conrad et al., 2004), and Morecroft et al. (2009) found significant decreasing population trends for moth species with more northerly European distributions at northern, upland sites in the UK Environmental Change Network.
In addition, several studies have found links between winter conditions and moth declines, indicative of climatic influence. Population levels of A. caja correlate closely, and negatively, with winter precipitation and mean spring temperature, suggesting a link between climate change and the severe decline (89% decrease in population index, 1968–2002) of this moth (Conrad et al., 2002). Furthermore, studies of moth declines in both Britain and the Netherlands found significant relationships between overwintering life-cycle stage and species trend; moths that overwinter in the egg stage had declined (on average) more than others (Conrad et al., 2004; Groenendijk & Ellis, 2011; and a similar result for butterflies in WallisDeVries & van Swaay, 2006). Species overwintering as larvae or pupae had also decreased, while species that are adults during the winter had, on average, increased in both countries.
Another effect of winter and early spring climate has been observed on Operophtera brumata winter moth populations in the Netherlands. The synchrony of larval hatching date with the availability of its larval food resource (bud burst of Quercus robur) decreased over time, because of larvae hatching in advance of bud burst (Visser & Holleman, 2001). The degree of synchrony was reduced by warmer spring temperatures combined with no change in the incidence of days with frost during the winter. Such asynchrony is predicted to cause a large increase in larval mortality, which is a major driver of population dynamics in this species. Thus, prolonged or high levels of asynchrony might cause population decreases in this moth species, although intense selection pressure to restore synchrony (or adaptive asynchrony) may rapidly redress this problem (van Asch et al., 2007; Both et al., 2009; Singer & Parmesan, 2010).
In contrast, climate change is also expected to benefit elements of Britain’s moth fauna. There is already some evidence for range expansion and increased abundance among southerly distributed moth species (i.e. those with a northern range margin in Britain). Morecroft et al. (2009) found that species with the most southerly distributions at the European scale showed significant increases in population levels at 10 sites in the UK. The moth species with the greatest population increases in Britain according to Conrad et al. (2006) also had increased distribution size, and the northern range margins of a sample of eight macro-moth species had shifted northwards considerably (mean, 79.5 km 10 year−1 northward shift, 1982–2009), rivalling the largest equivalent results for butterflies and Odonata (Hill et al., 2002; Hickling et al., 2005; Fox et al., 2011b). This intimates that southern moths may conform to the general pattern of poleward range expansions recorded among other taxa in Britain and globally (Hickling et al., 2006; Chen et al., 2011). The study by Salama et al. (2007) in central Scotland found that increasing moth diversity was positively correlated with mean annual temperature.
The absence of moth abundance decline in northern Britain compared with significant decreases in southern Britain appears to relate to a greater proportion of species with increasing population trends in the north (Conrad et al., 2006; Fox et al., 2006b; Scottish Government, 2007). This pattern is consistent with poleward range expansion and increasing abundance of some moth species through northern Britain in response to climate change. However, other factors, such as different patterns of land use and land-use change in northern Britain, could equally be responsible.
Other generally positive climate change impacts on moths in Britain include increased immigration (Sparks et al., 2005; Morecroft et al., 2009), colonisation (Parsons, 2003, 2010) and phenological change. The latter includes many examples of advancement and increased duration of flight period and additional generations in apparent response to climate warming, both in Britain and elsewhere in Europe (e.g. Fletcher, 2006, 2009; Salama et al., 2007; Altermatt, 2010; Pöyry et al., 2011).
In summary, although the evidence is limited at present, Britain’s moths appear to be responding to climate change in qualitatively similar ways to butterflies. There are suggestions of climatic effects leading to the decline of some species, but also clear evidence of apparently positive impacts on species populations and distributions. Future climate change may, of course, alter this balance if new conditions are unsuitable for moth species in Britain, plus the interaction between climate change and habitat loss, for example through sea-level rises, may damage specialist moth communities of coastal wetland habitats (e.g. Gortyna borelii Fisher’s estuarine moth; Ringwood et al., 2004).
Globally, non-native species are regarded as a principle driver of biodiversity decline and an ongoing threat to species and habitats (Mack et al., 2000; Manchester & Bullock, 2000; Gurevitch & Padilla, 2004; McGeoch et al., 2010). Many species of non-native plants, vertebrates and invertebrates are established in Britain, and there are numerous negative impacts on native biodiversity (Brown et al., 2008; Lack, 2010; Lever, 2010; Holt et al., 2011).
There have been no quantitative assessments of the impact of non-native species on moth populations in Britain. Nonetheless, negative effects might be expected via the influence of invasive plant species and introduced animals (e.g. deer) on habitat quality and larval hostplant resources. Examples of specific impacts include the invasion of semi-natural habitats of Zygaena loti slender scotch burnet, Z. purpuralis transparent burnet and Eudarcia richardsoni by Cotoneaster spp. shrubs (M. Parsons & T. Prescott, pers. comm.). Experiments in the United States found that non-native woody plants supported significantly lower abundance and species richness of moth and butterfly larvae than native trees and shrubs, even if the alien plants were in the same genus as the native hostplants (Burghardt et al., 2010). The impact of new predators is even more poorly understood, with species such as Harmonia axyridis harlequin ladybird and the parasitic fly Sturmia bella spreading rapidly and having the potential to impact on moth populations as well as other insects (Brown et al., 2011; Gripenberg et al., 2011).
Set against these examples is the success of some colonising and rapidly increasing moths that utilise non-native plants as larval hosts (Parsons, 2003, 2010; Conrad et al., 2006; Fox et al., 2011b). Lithophane leautieri Blair’s shoulder-knot, for example, utilises Cupressaceae trees and shrubs and, having become established on the south coast of Britain in the mid-twentieth century, spread rapidly northwards (146 km 10 year−1, 1982–2009) and increased substantially in abundance (16.5% year−1, 1968–2002). Other Cupressaceae-feeding moths show similar patterns, including recent colonists (e.g. Thera cupressata cypress carpet and Eupithecia phoeniceata cypress pug) and native species (e.g. T. juniperata juniper carpet and E. pusillata juniper pug). The latter moths were formerly restricted to semi-natural habitats where their only native larval hostplant Juniperus communis juniper occurs but, in recent decades, both moths have colonised many gardens in which ornamental Cupressaceae species have been planted (Waring et al., 2009).
Non-native species have not been directly linked with moth declines or extinctions in Britain as yet, although there is clear potential for negative impacts. On the contrary, non-native plants have enabled new moths to colonise Britain and a few native species to extend their distributions.
Exploitation of populations
Collecting of wild specimens of macro-moths was once an integral part of the natural history study of this taxon in Britain. In modern times, despite an increase in popular interest in macro-moths, collecting of specimens is less commonplace. Although over-collecting has often been postulated as a cause of decline or extinction for rare moths and butterflies in Britain, there is little evidence to support the assertion (Young, 1997; Asher et al., 2001), contrary to other taxa (Diamond et al., 1989; Roberts & Hawkins, 1999; Jackson et al., 2001; Rosser & Mainka, 2002; Dirzo & Raven, 2003). Indeed, the large population sizes, phased emergence and short lifespan of many moth species also make it theoretically unlikely that anything but highly organised, exhaustive collecting could impact on any but the rarest localised species. Nevertheless, responsible collecting is strongly urged by relevant UK organisations, and there is a widely accepted code of conduct (Invertebrate Link, 2002).
Young (1997) considered Z. viciae to be the only moth species for which there was credible evidence of extinction caused by collecting in Britain. After discovery in 1869, nine sites were found in the New Forest in southern England, attracting large numbers of collectors, and the moth became extinct in 1927. The extinction proved short-lived, however, as another, isolated colony of the moth was later discovered in Scotland. The precise location of this remaining colony has not been publicised to reduce potential damage from collecting.