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MUur<\LisL April 2017 Volume 142 Number 1094 # The Naturalist Vol. 142 No. 1094 April 2017 Contents Page An exceptional influx of the Diamond-back Moth in Yorkshire 1 in the spring of 2016 H. E. Beaumont and C. H. Fletcher Homage to Lloyd: revisiting a pioneering biogeographical paper in The 4 Naturalist * Robert A. D. Cameron Field Note: The Lealholm Proboscidean tooth Chris Pellant 12 Freshwater plants and SSSI canals in the East Midlands and North of 15 England 2: Chesterfield Canal, Cromford Canal and Grantham Canal R. Goulder The bats of Rockley Tramway Tunnel* Peter Middleton and Robert A. 33 Bell Calomicrus circumfusus (Coleoptera: Chrysomelidae) in Yorkshire - a 40 correction RJ. Marsh Gains and losses of species abundances of bees of Watsonian Yorkshire 41 Michael Archer Field Note: Drone Fly impaled on thistle Richard Shillaker 48 Species-rich neutral grassland management on roadside verges in 50 Burley-in-Wharfedale, West Yorkshire Robyn Guppy, Karl Harrison, Gordon B. Haycock The Mollusca of some ancient semi-natural woodlands in coastal N.E. 54 Yorkshire* A. A. Wardhaugh Yorkshire Ichneumons: Part 6 W.A.Ely 60 Excursion Circulars 2017 69 Book reviews 77 Calendar 80 Notices: pl4 YNU AGM 2017 p32 Staff changes Erratum: p60 An asterisk* indicates a peer-reviewed paper Front cover: Lealholm Proboscidean tooth (see pl2) Photo: Chris Pellant Back cover: YNU members Jill Warwick and Mike Denton talking to visitors to the YNU stand at the BTO Conference at the University of York, 18 March 2017. Yorkshire Naturalists' Union c/o NEYEDC, 10a Minster Gates, York YOl 7HL Tel: 01904 641631 Email: membership@ynu.org.uk Website: www.ynu.org.uk Registered Charity No. 224018 The Naturalist This publication is issued free to individual members of the Yorkshire Naturalists' Union and to Affiliated Societies. The Editorial Board of The Naturalist is currently: J. Bowers, W. Ely, A. Henderson, A. Millard, P. Simmons, D. 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Copying of more than one article or multiple copying of a single article is forbidden unless special permission has been obtained from the Yorkshire Naturalists' Union. Articles accepted for publication in The Naturalist may not be submitted to another journal for publication. Permission is granted for the use of brief quotations in published work provided that acknowledgement of the source is clearly stated but the use of substantial sections of text and any illustrative matter requires the express permission of the Yorkshire Naturalists' Union. The Naturalist is printed by Swallowtail Print, Norwich ISSN 0028-0771 The J\/<\jLuraXisL An exceptional influx of the Diamond-back Moth in Yorkshire in the spring of 2016 H. E. Beaumont 1 and C. H. Fletcher 2 ^7 Melton Green, West Melton, Rotherham, South Yorkshire, S63 6AA 2 The Forge, Hutton Conyers, Ripon, North Yorkshire, HG4 5EB For many Yorkshire lepidopterists the first indication of a sudden arrival of large numbers of the Diamond-back Moth Plutella xylostella (Linnaeus) came from the BBC natural history programme Springwatch transmitted from the RSPB reserve at Minsmere, Suffolk on 31 May, 2016, when considerable numbers were attracted to a mercury vapour moth trap operated at the site. Almost immediately this moth was recorded widely across the country, including Yorkshire, and the phenomenon attracted widespread publicity in the national media, where the emphasis was on the damage and economic repercussions that the moths could have on Brassica crops. The Diamond-back Moth (see Plate 1, centre pages) is a well-known immigrant and potential pest, perhaps originating in Asia Minor but which has been spread around the world by human activity and now occurs on every continent except Antarctica. It is recorded annually in varying numbers across Yorkshire and, although widespread, the totals involved are usually unremarkable. Periodically, however, it appears in numbers so great that the presence of the moth becomes apparent to the wider public. The major influxes of this species seem to come from northern Europe and are thus most evident in north and eastern England and in eastern Scotland. The 2016 influx was sudden and unexpected. The first hint was the arrival of unusual numbers in eastern and northerly parts of Yorkshire on 30 May. By the following day there were reports from all across the county and over the next few days numbers rapidly increased to record levels. Social media was buzzing with reports of huge counts. On 31 May Ian Marshall estimated 1250 in a single MV trap in North Ferriby and the following day Lenora Bruce reported 800 to a single actinic trap at Bridlington. On 2 June Jim Morgan, whilst walking across an area of damp long grass in Hornsea Town Park, flushed "clouds of Diamond-back with every step" - a conservative estimate was made of at least 4000 individuals. On 3 June Andy Hood reported over 3000 in one small area of Filey with similar numbers at Flamborough the The Naturalist 142 ( 2017 ) 1 following day. By 5 June the same observer estimated 20,000 in a single field at Flamborough and the same day Damian Money reported 1800 to light at Skinningrove and 1500 at Brotton. Although the largest numbers were seen in coastal areas, there were some impressive counts inland. Dave Hunton in Garforth noted on 8 June "this morning was the first time in over twenty years that I have seen anything like the number of moths in my trap; admittedly 90% were Diamond-back Moths! What an incredible sight. I've logged 1000 but this was a conservative figure". Numbers peaked in the first week of June then gradually declined, with 350 at Saltburn on 21 June (Damian Money) being the last big count. A smaller second peak of records occurred from late July, especially in the north-east of the county, with 350 by day at Fen Bog (Ian Marshall) on 24 July, 195 at Skelton (Damian Money) on 2 August and 171 at the same site on 6 August. These were presumably the progeny of the original migrants. After this numbers fell dramatically to normal levels with the last double-figure count of 14 at North Ferriby on 22 August and the last individual at West Melton on 1 November. The mass migration was not confined to Yorkshire and similar numbers were reported all across the country. On 7 June it was widely reported in the media that "a two-mile cloud of moths reported in Leominster...was like driving through rain". The national press was not to be left out, particularly in view of the referendum on Brexit due on 23 June. The Sun led the way with "Nasty Euro Moths hit UK" and "Time to Mothball the EU" on the front page of its 15 June edition; the inside pages urging the public to vote Leave in order to "protect our country...and our cabbages". The newspapers were seemingly unaware of the fact that the influx occurred during a period of north-easterly winds so the moths probably originated from parts of the Baltic region outside the EU! It was widely predicted that Brassica farmers would be badly affected and there was much media speculation that Brussels sprouts would be in short supply at Christmas. Again The Sun led the way with "Christmas dinners under threat as plague of Brussels sprout-eating moths invade UK". The Daily Telegraph countered with "Brussels sprouts could be off the menu this year as the crop could be ruined by a plague of immigrant moths invading the UK" but then misleadingly stated that the moth in question was known as "Cabbage Moth". By late summer, however, numbers of Diamond-back Moths had fallen to levels seen in an average year and fortunately (or unfortunately depending on your point of view) Christmas dinners did not appear to be significantly affected by a lack of sprouts. There were many articles in the media forecasting that crop damage was going to be bad but very few supported that these predictions had come true. An article in Lincolnshire Live entitled "Moth invasion wipes out 60% of Lincolnshire's sprout supplies" was misleading as the quote from the farmer was "We've actually had one field where we have thrown away about 60 per cent of the crop" so the damage overall will have been less. A "DEFRA spokesman" was reported in the Daily Express as saying "while the number observed this year is particularly high, there has been no significant damage reported in crops and a number of control methods are available for farmers" - which was rather glossing over the fact that control methods are poor. The moth seems to become quickly resistant to commonly used pesticides, in fact samples of Diamond-back Moths from Lincolnshire, Suffolk and Scotland were tested at Rothamsted Research and all were found to be resistant to pyrethroids. So, to sum up, despite resistance to some commonly used pesticides, in most cases damage was much less than predicted. 2 The Naturalist 142 ( 2017 ) The most severe recent outbreaks occurred in the years 1891, 1914 and 1958. Agassiz (1996) mentions a "great immigration in 1891 that whole fields of crops were destroyed in Lincolnshire". Arkle (1891) has a lovely story of how Mr. A.H. Paynter visited the Longstone Lighthouse (Fame Islands) on 10 July to find the surrounding rocks covered in moths and that the lighthouse keepers told him that they had to keep sweeping them off the light throughout the night so that it could be seen by passing shipping. Although Chu (1986) cites 1914 as a year when there was a large immigration of Diamond-back Moths into Britain, they seem to have been largely ignored by Yorkshire lepidopterists. The recent onset of the Great War perhaps deflected interest and observer effort. In fact the only mention traced is by T.A. Lofthouse when reporting on the YNU excursion to Eskdale in early August, who states "There were also a few Plutella cruciferorum, the 'pest' of the season about." A major outbreak of the species in 1958 saw spectacular numbers in northeast coastal towns from Berwick to Scarborough that caused chaos. Mackenzie (1958) reported that the moths entered houses in such numbers as to cause alarm, cyclists were forced to ride through swarms, and car drivers had to stop and clean their windscreens. Unfortunately at that period interest in the smaller moths in Yorkshire was almost non-existent and local information was derived from only a handful of observers. Frank Hewson, the YNU Lepidoptera recorder at that time, relates in his annual report for 1958 that during May many were reported right across the north of England but that myriads were yet to come. R.S. Pollard (the Scarborough Naturalists' Society moth recorder) wrote that on 2 June there occurred an incredible invasion of Plutella maculipermis (as the moth was then known) as far south as Withernsea with literally millions in both town and country. Several local farmers who omitted to spray lost all their swedes and kale. J. Briggs reported that on the morning of 30 June the moth made a sudden appearance with about thirty in his moth trap at Bradford. Towards the end of July and early in August considerable damage was done to Brassica plants and wallflowers by the larvae, of which seven or eight could be found on one cabbage leaf. He went on to say that the expected second brood did not appear and only occasional moths turned up in the trap subsequently. Further south J.H. Seago first noticed moths flying in his garden at Wath-on-Dearne in misty rain early in the morning of 3 July. By midday large numbers were at rest on bushes and plants and at each tap of the foliage a hundred or so would fly out; the garden must have contained several thousands of moths. By the following morning numbers had greatly reduced and only half a dozen could be found. It could perhaps be said that, although the 2016 influx was dramatic, it was by no means unprecedented and numbers in the past may have been even greater. One thing which possibly sets the 2016 event apart from minor influxes over the last 20 years is that there are often several small immigrations per year but this year it was just one huge influx and almost nothing afterwards. Most later season records were likely to have been due to second (and subsequent) generations but numbers seemed to be much fewer than would normally be expected and there was little evidence of further invasion. In that respect it was rather reminiscent of the 1958 influx. The Naturalist 142 ( 2017 ) 3 References Agassiz, D.J.L. (1996) Yponomeutidae - in The Moths and Butterflies of Great Britain and Ireland. Vol. 3. Harley Books, Great Horkesley. Arkle, J. (1891) The diamond-back moth ( Plutella cruciferarum). Entomologist 24: 256-260. Chu, Yau-I. (1986) The Migration of Diamondback Moth - in Diamondback Moth Management, Proceedings of the First International Workshop, Tainan, Taiwan, 11-14 March 1985: 77- 81. Hewson, F. (1959) Lepidoptera - in Yorkshire Naturalists' Union, Annual Report for 1958. The Naturalist 84: 12-15. Lofthouse, T.A. (1914) Lepidoptera - in Yorkshire Naturalists in Eskdale. The Naturalist 39: 322. Mackenzie, J.M.B. (1958) Invasion of diamondback moth ( Plutella maculipennis Curtis). Entomologist 91: 247-250. Homage to Lloyd: revisiting a pioneering biogeographical paper in The Naturalist Robert A.D. Cameron Department of Animal and Plant Sciences, University of Sheffield, S10 2TN. Email: r.cameron@sheffield.ac.uk Introduction Following a long-standing tradition, Lewis Lloyd-Evans ("Lloyd") published his 1974 Presidential Address to the YNU in The Naturalist : "The biogeography of snails in Yorkshire" (Lloyd-Evans, 1975). It is a short but wide-ranging account, dealing with many interesting records of land and freshwater molluscs in the county. It also includes a detailed account of his systematic sampling of tetrads (2km squares) within a single 10km square (Ordnance Survey 44:20, Penistone). Among other ways of analysing his data, he examined the relationship between the size of area and the number of species to be found in it, extending beyond the square to the then known fauna of increasing areas within Yorkshire and to the whole of Great Britain. Included in his analysis is a graph (his Figure 6) showing the relationship between the number of species of land and freshwater molluscs and the logarithms of the areas concerned. This kind of quantitative examination, species/area relationships (SARs hereafter) has a long history, but he was almost certainly unaware that his was the first attempt to do so for molluscs within a single land mass. These SARs have played a significant part in the development of biogeographical ideas (Rosenzweig, 1995) but the next attempts to analyse such SARs for continental as opposed to island molluscs did not appear until the end of the 20th century (Nekola and Smith, 1999; Cameron, 2002). His paper was not only a pioneering venture in this field; with some modifications in analysis and with the addition of a few later records, many obtained by Lloyd himself, his data shed light on some of the factors that influence variation in species richness among areas of the same size and enable us to examine some of the problems that arise in interpreting these SARs. We can now compare his results with those obtained elsewhere. In this paper, I give the context in which SARs give us important clues to the factors governing the distribution of 4 The Naturalist 142 ( 2017 ) animals and plants and then re-analyse Lloyd's data to explore some of the influences on land snail distribution at the scale he used. Lloyd was a man with many interests and skills in natural history (Obituary: The Naturalist, 127 (2002): 81-83). At a time of 'big data' and very sophisticated professional analyses, I pay homage to systematic and informed amateur observation, motivated by curiosity. Species/Area relationships (SARs) Assuming that sampling is adequate we naturally expect that, as we extend the area in which we make records, so the number of species we find will increase, even though the rate at which that happens might depend on scale and on the kinds of animal or plant we are interested in. According to Rosenzweig ( loc. cit.) the first attempt to look quantitatively at the way in which the number of species increased as the area considered got larger was carried out by H.C. Watson in 1859 on plants recorded in increasing areas from a part of Surrey to the whole of Great Britain. Over time, many more analyses have been carried out and the ways of expressing them have become standardised. The increase can be modelled as a power law: S = cA z , where S is the number of species, A is the area and c and z are constants. In practice, most analyses of SARs are performed using the equivalent equation: log S = z log A + log c. In this form, z is the slope of the relationship and log c is the intercept, the value of log S when log A is 0. To get a feel for what this means, a slope of 0.1 indicates that for a thousand-fold increase in area, the number of species has merely a twofold increase. A very large number of these SARs are now known; most have a slope considerably less than 1 (Rosenzweig, loc. cit.). In a classic account, Rosenzweig [loc. cit.) distinguished four kinds of SAR. Three concerned increasing areas of a landmass in which the results for small areas were included in the larger (so the slope could never be negative). At very small scales relative to the mobility of the organism, the slopes were relatively steep. At intermediate scales, the slopes were very shallow, but at very large scales they again steepened, often to the extent that the number of species increased in direct proportion to the area. The fourth was rather different; it concerned the relationship between number of species and the areas of islands in an archipelago. Here, each island is considered separately (so, in principle, a negative slope is possible: a smaller island may have more species than a larger). The explanations for these patterns are considered later but they are recognised as being among the most general patterns that we can find in nature (Rosenzweig, loc. cit.; Whittaker & Triantis, 2012). The area, the data and their analysis Lloyd-Evans [loc. cit.) gave a detailed description of his chosen 10km square. He described it as nothing exceptional, containing no great rarities: "an oasis of pleasant, unspoilt countryside in a district scarred by industrial development". He chose it for its very ordinary character. The range of altitude is 70-360m asl (Fig. 1). The rocks are mainly sandstones of the Coal Measures and Millstone Grit, all of Carboniferous age. The lack of limestone makes it a relatively hostile environment for snails. Within this square he sampled each tetrad (2km square) at roughly the same intensity, visiting each several times. He presented his data in the form of a table (his Figure 1), listing all the species found within the 10km square and showing in which tetrads each had been found. His The Naturalist 142 ( 2017 ) 5 list included freshwater as well as terrestrial molluscs and he presented simple maps indicating the distribution of species among tetrads. To construct his SAR, he worked out the average number of species in areas of increasing size within the 10km square and extended the range by using data for larger areas within Yorkshire, Yorkshire itself and the whole of Great Britain. Following a number of other studies at the time, he plotted the actual number of species (not its logarithm) against the log of the area. His figure 6 shows a remarkably tight fit of points to a regression line, with a correlation coefficient of 0.99! He noted that the number of species found in each tetrad varied considerably and that freshwater ones were particularly frequent in tetrads containing substantial water bodies. I used his original data in a more general paper on molluscan SARs in Britain (Cameron, loc. cit.). Shortly after his paper was published a small number of unpublished additional records were made, many by Lloyd himself. Adrian Norris has made these available to me, and they are included in what follows. The data used here thus differ slightly from those in Lloyd-Evans [loc. cit.) and Cameron [loc. cit.). As in 2002, I have considered only the land molluscs. Apart from the fact that Lloyd noticed the very uneven distribution of freshwater snails among tetrads, the restriction enables us to compare the results with others using land molluscs only. For the same comparative reason I have used the logarithms of both the number of species and area. As Rosenzweig {loc. cit.) remarks, the log/log plot is now the standard for nearly all SAR studies and one can compare slopes among them. Beyond the average number of species in each tetrad (4km 2 ), Lloyd used the average for intermediate areas of 20km 2 but did not say how he chose such areas or whether they overlapped. Of necessity, there is only one figure for the whole 10km square. It is worth noting here that 'average' is a rather slippery term. The average (i.e. mean) richness of all tetrads is in itself straightforward, though potentially misleading (see below), but the averages for larger areas within the 10km square are more problematic because if all possible sets of such areas are considered, even if restricted to squares of contiguous tetrads, there are overlaps in the areas concerned so that some tetrads will contribute more to the final estimate than others. I have estimated the mean richness of all possible sets of square intermediate areas (4 tetrads, 16km 2 ; 9 tetrads, 36km 2 ; 16 tetrads, 64km 2 ), but I have also given the maximum and minimum species totals recorded for each size of square. Maximum figures have been used in some other analyses (Cameron, loc. cit.). Lloyd sang the praises of the Ordnance Survey and used the 1:25,000 map to estimate the amount of cover provided by different habitats: woods, agricultural and urban. I have re¬ evaluated woodland cover, distinguishing between coniferous and deciduous woods, but for each tetrad separately, using a map roughly contemporaneous with his survey. I have also used data on the range of altitude within each tetrad and the proportion of land within it lying above 200m. Thus, the analysis can be taken beyond the estimation of an SAR to account for variation in the number of species in each tetrad. These analyses generally use ranks rather than actual values to avoid statistical pitfalls, using Spearman's p. 6 The Naturalist 142 ( 2017 ) 10 E J P U Z 08 nfi D 1 N T Y 04 C H M S X 02 B G L R W * A F K Q V 00 20 22 24 26 28 30 Fig. 1. A topographical map of Ordnance Survey square 44:20, Penistone, with the tetrads within it identified by letters as in Lloyd-Evans (1975). Shading is at 50m intervals. 100 ISO 200 250 300 350 Results The topography of the square and the position of each tetrad are shown in Fig. 1, using the alphabetical system employed by Lloyd. Table 1 shows the species records and environmental details for each tetrad. Species are arranged in descending order of frequency. Names have been adjusted to conform to the latest British and Irish checklist (Anderson, 2008). 47 species have been recorded overall (13 slugs and 34 snails). The overall pattern, as noted by Lloyd, is one in which very frequent species (15, 32%, occurring in more than 80% of tetrads) and infrequent species (also 15, 32%, occurring in less than 20% of tetrads) outnumber those occurring in each of the intermediate 20% bands. Ten species occur in all the tetrads. Table 1. The total number of mollusc species, the highest and lowest points, the percentage of land over 200m and the percentage occupied by deciduous woodland in each tetrad of the Penistone square. Note that a full version of this table, showing all mollusc species found in each tetrad, is available at http://www.ynu.org.uk/naturalist. Tetrad A B C D E F G H 1 J K L Species total 21 18 15 19 25 23 22 17 25 23 18 23 Highest point m 350 330 350 330 280 360 350 310 270 220 320 270 Lowest point m 210 210 230 200 180 190 190 170  7.2 4.8 1.2 0.9 6.4 5.3 2.2 1.4 Tetrad M N P Q R S T U V W X Y Z Species total 23 33 27 22 29 28 24 27 26 24 33 28 28 Highest point m 270 190 240 300 260 270 180 215 250 230 190 150 170 Lowest point m 150 105 130 160 150 140 85 80 140 120 100 80 65 % above 200 m 70 0 20 70 65 25 0 10 55 20 0 0 0 % deciduous woods 3.2 7.1 11.3 4.2 7.1 11.2 9.2 15 7 10.5 20.5 5 13.2 The Naturalist 142 ( 2017 ) 7 Table 2. The means and ranges of numbers of slug and snail species recorded in areas of different sizes within the Penistone square, and the ratio of least to greatest richness overall. N is the number of square areas considered in each case. Area Km 2 N Mean slugs Range slugs Mean snails Range snails Mean all Range all Ratio 4 25 8.6 5-11 15.5 8-24 24.1 15-33 1:2.2 16 16 10.7 9-12 22.6 17-29 33.3 27-39 1:1.4 36 9 12.1 11-13 27.9 22-33 40.0 35-45 1:1.3 64 4 13 13 31.8 30-34 44.8 43-47 1:1.1 100 1 13 n/a 34 n/a 47 n/a n/a Table 2 shows the details of the species richness found in each area category. It is obvious, as expected, that species richness increases with size of area whether we look at slugs, snails or both combined, and this increase happens whether we consider the mean, the maximum or the minimum for each case. There is, however, another trend in these figures. The proportionate range of counts for individual areas within each size class decreases as the class itself increases. This is in part a statistical artefact: there are fewer examples of the larger size classes and they increasingly overlap. At the limit (the whole 10km square), we have only one value. However, there is no overlap among the tetrads and the evidence is that they differ considerably among themselves. The obvious consequence of these differences is that while there is a positive SAR in all cases (Fig 2), explaining more than 95% of the variation among sizes of area (the R 2 values in the figure), the slopes differ greatly among the relationships shown by using minimum, average or maximum richness. While the meaning of these differences is discussed later, it prompts questions about the variation shown among the tetrads. While we cannot dismiss the possibility that inadequate or variable sampling efficiency makes a contribution (Cameron & Pokryszko, 2005), any environmental correlations with richness will suggest that there is real variation in richness among tetrads. Fig.2. The species/area relationships within square 44:20 using maximum, mean and minimum values of richness for each area category. The slopes and R 2 values are shown. The large black circle represents the value for the whole square. There is a strong association between species richness and minimum altitude within each tetrad (the lower, the more species. Table 3). There are similar, but weaker, negative 8 The Naturalist 142 ( 2017 ) relationships with the maximum altitude and the proportion of the tetrad above 200m. There is also a strong positive association between species richness and deciduous woodland cover. Including coniferous woodland weakens this relationship; coniferous woods are hostile for snails. The two features, altitude and deciduous woodland cover, are themselves strongly associated. While ranking removes some possible statistical artefacts it can obscure the shape of a relationship. Fig. 3 shows that while the relationship with altitude is roughly linear, that with woodland cover is better expressed as a logarithmic relationship; there appears to be something approaching a threshold of woodland cover above which further increases have little effect. Table 3. The values of Spearman's p for the association of ranked values of species richness with deciduous woodland cover and the lowest point in each tetrad (lower points ranked higher), and between the two environmental factors. All are highly significant. Association Spearman's p P Richness/Woodland 0.849 <0.001 Richness/Lowest point 0.805 <0.001 <0.001 Woods/ lowest point 0.822 Fig.3. A: the regression of species richness on minimum altitude among tetrads. B: the regression of species richness on the proportion of deciduous woodland cover. In B, the regression lines are shown both for the linear relationship and for species richness on the logarithm of woodland cover. The logarithmic relationship is curved because the scale is arithmetic. The values of R 2 indicate the amount of variation accounted for by the relationship. For deciduous woods, the logarithmic relationship is a better fit. I have not so far mentioned differences in these associations between slugs and snails. The known slug fauna of Britain has increased considerably since Lloyd conducted his survey (Rowson et a!., 2014). Using the list recognised at the time (Walden, 1976), the 13 slugs recorded in the 10km square represent 50% of those deemed to be native to Britain, whereas the 34 snails represent 37% of the number of known natives. Eleven slugs were found in the richest tetrad, 42% of the then known national fauna, compared with 24 snails, 27% of the The Naturalist 142 ( 2017 ) 9 national fauna. Five out of the ten species found in all tetrads were slugs. These differences, though small, suggest that slugs may be more widely distributed at these scales than are snails. Discussion When a SAR is constructed according to Rosenzweig's ( loc. cit.) rules (larger areas must include the smaller), it is obvious that any variation in richness at the smallest scale will mean that the slope obtained will depend on the starting point chosen when the end point is the same in each. As I have pointed out elsewhere (Cameron, loc. cit.), there are many areas of less than lkm 2 in Britain that hold more species than found in the richest of Lloyd's tetrads and a few that hold more than have been found in the whole of his 10km square. It is indeed an "ordinary" square, lacking limestone or significant undisturbed wetlands. While incomplete sampling may account for some differences in richness among small areas identical in size, it is evident from Lloyd's data that even at this scale (tetrads) richness is affected by the range of habitats: lowland is richer than upland; well-wooded areas are richer than those with less, though there is a threshold effect. As the size of area is increased it is more likely to include the best habitats. At the very smallest scales this is something recognised by Rosenzweig {loc. cit.), who pointed out that in this case areas such as lm 2 quadrats will necessarily miss the whole range of habitats present in larger areas, and that therefore slopes of SARs will tend to be steeper at these scales. The point at which they flatten out will depend on which organisms are being considered and the scale, or grain, of habitat heterogeneity. Like many areas of Britain, the Penistone square contains a mosaic of habitats such that some may be missing even from a tetrad while present in the larger 10km square. What this shows is that the neat, linear SARs obtained in many studies apply over only a part of the scale over which studies can be made. In the specific case of snails, I attempted to deal with this by using the maximum values of richness for areas less than 100km 2 (Cameron, loc. cit.). Using Lloyd's original data and extending beyond his square up to the total British fauna, I found a value of z, the slope, of 0.133. Including data added here this decreases slightly to 0.127. The value is close to, but a little steeper than, values based on starting points on the Isle of Wight (0.083) and Suffolk (0.107), reflecting the slight decrease in richness northwards in Britain, but where the end point (the whole of Britain) is the same in each case. What is noteworthy about these values is that they are remarkably similar to that obtained for breeding birds (0.110) by Gaston & Blackburn (2000), starting with a small wood in Berkshire and extending to Britain as a whole. These low values suggest that Britain is relatively homogeneous, biogeographically speaking; most species of both birds and snails have managed to spread over most of the country, occupying those places that are suitable. As Lloyd commented, there were no rarities in his square; it was indeed a typical chunk of countryside. Snails have proverbially poor powers of active dispersal and suitable microhabitats often change over very short distances. Hence it comes as no surprise that the slopes of SARs are much greater in very small-scale studies. Mysak et al. (2013) found z values of 0.325 and 0.373 when moving from areas of 0.062m 2 to 0.562m 2 within fens and forests respectively. But within quite small areas of similar habitat, the slope flattens; Cameron {loc. cit.) found z values in the range 0.07 to 0.13 over an area range from less than lm 2 to a few hundred m 2 within a number of habitats. These are not meaningfully different from those reported for the much larger areas 10 The Naturalist 142 ( 2017 ) considered here but have a different cause. The heterogeneity of richness at the tetrad scale in the Penistone square reflects the particular scale of habitat heterogeneity rather than the dispersal powers of snails. The greater proportion of slugs among those species most widely distributed may, however, reflect their accidental dispersal by us in horticultural and other exchanges. While I have used Lloyd's data in more ways than he did in his original paper, it is the quality of those data and the inspiration that led him to sample in the way that he did that make such analyses possible. It took others a quarter of a century to catch up. Building on such work is my tribute to informed and thorough amateur observation. Acknowledgements Adrian Norris gave me background information on Lloyd's survey and provided me with other records made by Lloyd and himself a few years after the survey was published. References Anderson, R. (2008) Annotated list of the non-marine Mollusca of Britain and Ireland. Available from: www.conchsoc.org/node/540. Cameron, R.A.D. (2002) Some species/area relationships in the British land mollusc fauna and their implications. Journal of Conchology 37: 337-348. Cameron, R.A.D. & Pokryszko, B.M. (2005) Estimating the species richness and composition of land mollusc communities: problems, consequences and practical advice. Journal of Conchology 38: 529-547. Gaston, K.J. & Blackburn, T.M. (2000) Pattern and process in Macroecology. Blackwell Science, Oxford. Lloyd-Evans, L. (1975) The biogeography of snails in Yorkshire. The Naturalist 100:1-12. Mysak, J., Horsak, M., Svobodova, E. & Cernohorsky, N. (2013) Small-scale distribution of terrestrial snails: patterns of richness and abundance related to area. Journal of Molluscan Studies 79: 118-127. Nekola, J. & Smith, T. (1999) Terrestrial gastropod richness patterns in Wisconsin carbonate cliff communities. Malacologia 41: 253-269. Rosenzweig, M. (1995) Species diversity in space and time. C.U.P., Cambridge. Rowson, B., Turner, J., Anderson, R. & Symondson, B. (2014) Slugs of Britain and Ireland: identification , understanding and control. Field Studies Council, Telford. Walden, H.W. (1976) A nomenclatural list of the land Mollusca of the British Isles. Journal of Conchology 29: 21-25. Whittaker, R.J. & Triantis, K.A. (2012) The species-area relationship: an exploration of that "most general, yet protean pattern". Journal of Biogeography 39: 623-626. The Naturalist 142 ( 2017 ) 11 Field note: The Lealholm Proboscidean tooth Chris Peiiant Email: candhspellant@yahoo.co.uk Introduction In October 2016 a proboscidean tooth was discovered on the hillside above Lealholm village in the Esk Valley of North Yorkshire (VC62). Lealholm is about 10 miles inland from Whitby. This field note records the finding and briefly discusses the condition, identification and possible origin of the tooth and considers other similar finds in this area. Graham Featherstone of Lealholm, Whitby, provided this information about its discovery: "A friend of mine mentioned to me that he had found a large fossil whilst clearing out a ditch at his home above Lealholm. He had no idea what it was. A friend of his, who happened to be a vet, called at his house and suggested that the fossil was a mammoth's tooth. Knowing I was a keen naturalist, the finder mentioned the tooth to me and I asked if I could borrow it to take photographs. The tooth was shown to a geologist friend of mine (Chris Pellant) and he confirmed that it was possibly a mammoth's tooth. Having no interest in the tooth, the original finder gave it to me and it is now proudly in my possession." Location, size and condition The site of the ditch in which the tooth was discovered is almost exactly on the 180m contour line above and to the north of Lealholm village. Here, the floor of the Esk Valley is some 100m asl. The ditch cuts through about 10cm of peaty soil below which, to a depth of lm, the sediment in which the tooth was found is a fine-grained clay with numerous angular fragments of local sandstone up to 15cm in size. It may be relevant that during the most recent glaciation, ice came into this area from three main directions. Boulder clay containing erratics of granite from Shap was brought from the west; ice also moved from the north and left behind erratics from Northumberland, including Whin Sill and Cheviot rocks, and ice came from the east across the North Sea area, bringing with it fragments of rhomb porphyry. At Lealholm there is a moraine that blocked the valley and possibly ponded water to the west, ice filling the valley to the east. The high ground of the North York Moors is thought to have been free from ice, though it would have been tundra-like, no doubt with permafrost conditions. The tooth, which weighs 6.6kg and is 22cm x 32cm, is mainly pale grey, as can be seen from the photographs (see front cover and Plate 2, centre pages). In this it differs from many of the more brown-coloured Pleistocene proboscidean teeth which are not uncommon in outwash gravels and glacial sands farther south in Yorkshire (the Holderness coast, for example), Lincolnshire, Norfolk and the east Midlands. The whitish colouring may be due to mineralization, possibly by calcite (CaC0 3 ). This process could also have increased its weight slightly. Stuart Ogilvy, of the Yorkshire Museum, suggested that the mineralization may take up to a million years (pers.comm.). The grinding surface of the tooth is rather worn, possibly indicating that the animal was reasonably mature. The tooth has slight grooves and a 'crazed' 12 The Naturalist 142 ( 2017 ) pattern on its surfaces. This could be due to exposure to the influence of frost and wind on a tundra or permafrost surface over a considerable time. Identification It was not difficult to identify the tooth as that of a mammoth or related animal, but a more specific identification was initially not possible. However, the fortuitious arrival of the Yorkshire Geological Circular no 603 which summarised the paper Doggerlarid Mammalian Remains in a Broader Context by Prof. Thijs van Kolfschoten of Leiden University, The Netherlands, enabled me to take the next step in specific identification. I contacted Prof, van Kolfschoten and he commented on the 'interesting find' and forwarded my images to his colleague Dr Hans van Essen, an expert on mammoth remains. Dr van Essen, though always careful to point out that identification from photographs can be 'a bit tricky', commented that the tooth was possibly from the left upper jaw of a mammoth, probably not a straight-tusked elephant Palaeoloxodon sp. which, though not uncommon in some parts of England such as the Cromer Forest Bed Formation in Norfolk, tends to occur in interglacial deposits. There are two mammoths with advanced dental morphology - the Steppe Mammoth Mammuthus trogontherii (Pohlig, 1885) and the Woolly Mammoth M. primigenius (Blumenbach, 1799). These are found more recently than 0.7 million years ago. Initially, Dr van Essen gave it as his opinion that the tooth from Lealholm is probably from the Steppe Mammoth. However, on examining images I emailed to him of the front roots of the tooth, he later suggested that it could be a 'rather rare early Woolly Mammoth or a late Steppe Mammoth/ The tooth has the appearance of middle Pleistocene mammoth molars from the Netherlands (Wolstonian interglacial 352,000 to 130,000 years ago) and the tooth is much heavier and more massive than those from the most recent Devensian glacial episode popularly known as the Ice Age (110,000 to 12,000 years ago). Dr van Essen suggested that the Lealholm proboscidean tooth may be from an animal that lived c.200,000 years ago, before the most recent glacial advance into this area of North Yorkshire, and that its remains, including the tooth, were caught up in later moraine movement and deposition. Certainly this is the case with mammoth teeth from boulder clay in Norfolk containing Scandinavian erratics. Such fossils could have been frozen into the ground over which an ice sheet moved and may then have been picked up by moving ice and carried along. However, to prove definitely from which animal the tooth came, its age should be determined. Dr Van Essen contacted Prof. Adrian Lister at the Natural History Museum, as he is interested in any British mammoth finds. Prof. Lister says that the age of the tooth should be ascertained either by sediment analysis or radio-carbon dating, to prove whether it's from a mammoth or possibly an Asian Elephant Elephas maximus. Other local finds Proboscidean remains are not common in the area and, though a number of museums have been contacted to try to establish field locations for North Yorkshire mammoth fossils, identification of these specimens may not be up to date, especially as many records are historical. Molars labelled 'elephant' are recorded from Kirkdale Cave in 1823 (Buckland, 1823). These have since been deemed to be from a straight-tusked elephant which is typical of an 'Ipswichian' warm interglacial fauna (Boylan, 1981). Many local records tend to be catalogued as Woolly Mammoth and, though North Yorkshire museums hold numbers of such fossils (see Rutter, 1956), it would seem that few have field The Naturalist 142 ( 2017 ) 13 locations. The Dorman Museum in Middlesbrough holds a mammoth tooth collected in 1934 at the now defunct Barmpton quarry near Darlington. Also from Barmpton is a fragment of tusk found in 1978. This is now in the Tyne and Wear Museum. Further tusk remains have been found at Hartlepool Docks (Jessop, 2013) and Robin Hood's Bay (Young, 1822; Bevan, 1909). Acknowledgements Thanks must be extended to Colin Howes (Convenor and Recorder of the Mammal Section of the YNU), who has taken great interest in the tooth and encouraged the writing of this field note. He has helped with references and read through the article in draft form. Zoe Wilson (Dorman Museum, Middlesbrough), Stuart Ogilvy (Yorkshire Museum, York), Will Watts (Scarborough Museum) and Roger Osborne (Whitby Museum) all provided information. Special thanks to Prof. Thijs van Kolfschoten and Dr Hans van Essen of Leiden University, The Netherlands. My wife, Helen, has read the original text and made corrections. References Bevan, D.W. (1909) Mammoth's Tusk at Robin Hood's Bay. The Naturalist 34: 270. Boylan, P.J. (1981) A new revision of the Pleistocene mammal fauna of Kirkdale Cave, Yorkshire. Proceeding of the Yorkshire Geological Society 43: 253-280. Buckland, W. (1823) Reliquiae Diluvianae. Murray, London. Jessop, L. (2013) Extinct mammals from the Pleistocene (p. 183-184) in Bond, I. (ed) Mammals, Amphibians and Reptiles of the North East. The Natural History Society of Northumbria. Newcastle. Rutter, J.G. (1956) The Mammals of the Pleistocene and Prehistoric Times (pages 419-430) in Walsh, G.B. and Rimington, F.C. (eds) The Natural History of the Scarborough District. Vol. 2. Scarborough Field Naturalists' Society, Scarborough. Young, G. (1822) A Geological Survey of the Yorkshire coast. Whitby. YNU Notice: Annual General Meeting The next Annual General Meeting of the Yorkshire Naturalists' Union will be held in the Wolfson Room at the Bramall Learning Centre in the Royal Horticultural Society Garden Harlow Carr, Harrogate, on Saturday 18 th November 2017. 