\ A QUARTERLY JOURNAL OF NATURAL HISTORY FOR THE NORTH OF ENGLAND irW V V » * Yorkshire Mayflies — Leslie Magee Otters ( Lutra lutra L.) as Scavengers: an Experiment — Ray Hewson Aculeate Wasps and Bees (Hymenoptera: Aculeata) of Blaxton Common in Watsonian Yorkshire with the Introduction of a New National Quality Scoring System — Michael E. Archer Some Records of Feather Mites (Acari: Astigmata) in Yorkshire — Barry Nattress A Sub-fossil Record of Pomatis elegans (Muller), a Mollusc Previously Unrecorded in the East Riding of Yorkshire — R. Middleton and B. R. Kirk Vertigo geyeri (Lindholm 1925), a Snail New to Yorkshire — David J. Lindley Road Verge Halophytes in S. E. Yorkshire — Peter J. Cook Published by the Yorkshire Naturalists’ Union Editor M. R. D. Seaward, MSc, PhD, DSc, FLS, The University, Bradford BD7 1DP Notice to Contributors to “The Naturalist’ Manuscripts (two copies if possible), typed double-spaced on one side of the paper only with margins at top and left-hand at least 2.5cm wide, should be submitted. Latin names of genera and species, but nothing else, should be underlined. S.I. Units should be used wherever possible. Authors must ensure that their references are accurately cited, and that the titles of the journals are correctly abbreviated. Volumes of The Naturalist for the years 1886 to 1975 have been retrospectively numbered 11 to 100 to accord with numbering before and after this period (see YNU Bulletin no. 3, pp. 21-22 1985); please cite these volume numbers in all references. Table and text-figures should be prepared on separate sheets of paper. Drawings and graphs, drawn about twice the linear size they are to appear, should be in jet-black Indian ink, and legends should not be written on the figures. Publishable manuscripts not conforming to the above requirements will be returned for alteration. Photographic Plates Readers of The Naturalist will have noticed that the number of photographic illustrations has increased in recent years. Good clear photographs, suitably captioned, to accompany articles or as independent features are always welcome. To encourage this development, a long-standing member of the YNU, who wishes to remain anonymous, has most generously offered to make a donation, the income from which would finance the publication of a plate or equivalent illustration in future issues whenever possible. The editor, on behalf of the YNU, wishes to record this deep appreciation of this imaginative gesture. ©Yorkshire Naturalists’ Union — 1995 Single Copies may be made of single articles in this journal provided that due acknow- ledgement is made and the copies are for non-profit making educational or private use. 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. 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. All matters other than subscriptions should be addressed to: Mr John A. Newbould, Tapton House 30 Moorlands, Wickersley Rotherham S66 OAT Items which should be sent to the above include: All membership applications, changes of address, resignations and problems concerning non-receipt of any of the YNU’s publications. Please quote the membership number printed underneath your address on all correspondence. Subscriptions (unless covered by Banker’s Order) should continue to be sent to: Mr Derek Allen, c/o Doncaster Museum, Chequer Road Doncaster DN 1 2AE The Naturalist is issued free to individual members of the Yorkshire Naturalists’ Union and to Affiliated Societies. Institutions and Subscribers £20.00 Registered Charity No. 224018 A QUARTERLY JOURNAL OF NATURAL HISTORY FOR THE NORTH OF ENGLAND Editor M. R. D. Seaward, msc, PhD, DSc, fls The University, Bradford BD7 1DP Volume 120 1995 Published by the Yorkshire Naturalists’ Union 3 YORKSHIRE MAYFLIES LESLIE MAGEE Presidential Address to the Yorkshire Naturalists' Union, Doncaster, 3 December 1994 I begin this address with a quotation by the Rev. A. E. Eaton in his 1883-88 monograph on the Ephemeridae : “On many accounts these insects are very eligible subjects for scientific research: but so long as they are ill known, and their exact identification is a matter difficult of accomplishment, their employment in any branch of zoological learning is surrounded with disadvantages too patent to need identification.” This quotation is highly significant in relation to the content of the remainder of my address. The name Ephemeroptera comes from the Greek Ephemeros , lasting for a day; pteron, wing. The Germans call the insects Eintagsfliegen, the one day fly; the French, Ephemere. The common name ‘mayfly’ is today applied generally to all British species, notwithstanding an unsuccessful attempt in recent years to rename them dayflies. Originally, anglers applied the name ‘mayfly’ to the two best known and the largest species, viz. Ephemera danica and E. vulgata. The name ‘mayfly’ was given to the larger species of stoneflies and to the larvae known as stonefly ‘creepers’ and this name still applies in some parts of northern England. The habits of the stoneflies and the descriptions of the insects in angling literature are numerous and do not give rise to confusion today. The main hatch of these two species is during June, when they are greedily devoured by birds and fishes. The reason for the insects not being called ‘juneflies’ rather than mayflies is that during the period when the Julian calendar was in use the peak period of the hatch was towards the end of May. History About 2,400 years ago the Greek philosopher Aristotle wrote briefly about an animal which emerged from a river near the Black Sea. It had four wings, four feet and had a life span of only one day. It was called Ephemeron, i.e. one day living. About 200ad Claudius Aelianus repeated the same story with a description of catching trout or grayling in a river in Macedonia with an artificial fly made of wool and feathers. Occasional mention is made in the translations of the classics of the animal Ephemeron , but it is not until the 15th century that there appeared descriptions of insects which we may confidently judge to be mayflies. Julius Caesar Scaliger (1484-1558) described an aquatic insect with a split tail (two or three ends) which was almost certainly a mayfly. In 1496 Wynkyn de Worde, a pupil of Caxton, printed at Westminster The Treatise of Fishing with an Angle. The author is unknown but it has been attributed to Dame Juliana Berners, an Abbess oT St. Albans. It is famous for the description of twelve artificial flies, copied from natural insects, and the months of the year when they were to be used. The Maure (Mulberry-coloured) Fly and the Tandy with a body of tan coloured wool and wings of the lightest feather of the mallard can be nothing but two copies of the Mayfly in different states (imago or sub-imago). These patterns, known as the Drakes, were plagiarised by generations of writers of angling books until the end of the 18th century. The Entomologists In 1634, a Dutchman, Outgert Cluyt (Augenius Clutius) published a book which described and illustrated (although not very well) an insect which hatched in vast numbers on the Rhine. After this date there was no doubt whatever what animal was intended by Ephemeron. Forty years later Jan Swammerdam published his marvellous description of the life history of the mayfly Palingenia longicauda under the title of ‘Ephemera Vita’. This insect, which is now extinct on the Rhine, hatched in millions (‘as thick as snow flakes in winter’). In 1903, Professor L. C. Miall, a former President of the Yorkshire Naturalists’ Union, wrote The Natural History of Aquatic Insects and devoted a whole chapter to the Mayflies. Naturalist 120 (1995) 4 Yorkshire Mayflies This included a translation of Swammerdam’s work which described in detail the anatomy of the insects and their life cycle. In the same chapter Miall quoted the writings of Reaumur on the mayfly, taken from the 12th memoire of his sixth volume of The History of Insects. By the end of the 18th century, 16 of the now known total of 48 recognised British species had been given scientific names by entomologists, but there was another group of people working on the natural history of aquatic insects. These were the angler-naturalists, almost entirely amateurs among whom, perhaps, the best known to naturalists is Charles Cotton, because his work is included in the later editions of The Compleat Angler written by his friend Izaak Walton. This work, said to have been written in less than a week, was Part 2 of The Compleat Angler published in 1676 and was entitled ‘How to angle for Trout and Grayling in a Clear Stream’. The work lists artificial flies for every month of the year and gives a description of the mayfly’s short existence as a winged insect. Cotton was educated at Cambridge and lived the life of a country gentleman (albeit impoverished) at Beresford Hall, situated closed to the banks of the R. Dove in Derbyshire. During the exuberant days after Waterloo the country came to life and there was a spate of books on all aspects of natural history, partly inspired by the writings of Gilbert White of Selbome and his contemporaries, several of whom were members of the Royal Society and who were to become members of the Linnean Society, founded in 1788. Simultaneously there appeared books on angling, shooting and hunting; the earlier works were mostly mere copies or blatant plagiarisms passed off as original works but now, with the opportunity to travel freely, came new authors. Most of the books were poorly illustrated, making identification of aquatic insects difficult. Suddenly out of the blue in 1836 came a book that made easier identification of the common insects seen on or around water. It was the The Fly -Fisher's Entomology by Alfred Ronalds. The hand-coloured copperplate engravings have never been surpassed, making it possible for some species to be identified with certainty from the plates alone; moreover the scientific classifications were accurate for the period, following those of Linnaeus (although the orders and genera have in most cases been superceded). Ronalds’ observations were made on the little R. Blithe in Staffordshire where he built an observatory at the water’s edge, with windows so obscured that the feeding trout were undisturbed. There were others in Yorkshire observing and recording in detail the insects which were the food of the trout and grayling, all keen naturalists in their own way; among these were William Pilling of Pool Mill, List of Flies for ye River Wharf e, 1794; John Swarbrick, Farmer of Austby, List of Wharf edale Flies , 1807; T. C. Hofland, The British Angler’s Manual , 1839; Michael Theakston, A List of Natural Flies taken by Trout , Grayling and Smelt in the streams ofRipon, 1853. Hofland was a wealthy landscape artist who often stayed at the shooting lodge at Bolton Abbey as a guest of the Duke of Devonshire but who also travelled widely throughout the British Isles. Theakston was bom at Ripon in 1786 and died there in 1866. His book is remarkable for the excellent engravings of terrestrial and aquatic insects which were drawn from life over a long period of time. The observations were made mainly on the Yore and the little R. Skell which flowed past his house in Waterskellgate. The publication of Ronalds’ work did not solve the problem of identification because the use of local and vernacular names continued until well into the 20th century; moreover they were applied to different insects in different parts of the country and the commoner the insect the more names there were. Some, like that of the Greendrake, E. danica , go back to the Treatise and there are others, such as the Primrose Dun, Heptagenia sulphurea , of whose identification there can be no doubt; we can obtain some idea of their distribution and abundance in the past from studies of the angling literature (Magee 1994). The Yorkshire Entomologists The results of the work of the Yorkshire entomologists were somewhat meagre and scattered and there was no published list of Yorkshire records. Eaton’s monograph Yorkshire Mayflies 5 (1833-88) referred to earlier had a few records from the North of England but none from Yorkshire. The Ephemeroptera were apparently totally neglected by the naturalists in Victorian times and no list appears in the Victoria County History for Yorkshire published in 1907. The first published list of Yorkshire mayflies was that of Prof. E. Percival and H. Whitehead in the The Entomologist’ s Monthly Magazine in 1927. The list appeared in the same year as the death of Geo. T. Porritt. George T. Porritt (1848-1927) had dominated the Entomology Section of the YNU over a long period of time. He made his first contribution to The Entomologist in 1865 when still a youth of 17. By 1870 he was becoming a recognised authority on Yorkshire Lepidoptera and in 1 872 became a Fellow of the Linnean Society. Having seen the demise of The Naturalist (1865-67) and the Yorkshire Naturalists Recorder (1872-1873), he made another bid for success in August 1875 with the launching of The Naturalist under the joint editorship of Charles P. Hobkirk and G. T. Porritt. Porritt’s name was to appear on the title page as an assistant editor for another 51 years. He was President of the Union in 1900. Porritt was a dedicated collector of insects and welcomed specimens from other collectors. In 1897 he made a request in The Naturalist for specimens of the Neuroptera and the Orthoptera but specifically excluded the Ephemeridae (sic) {Mayflies}, “which I do not propose to touch for the present”. In 1920 Porritt wrote in his annual report in The Naturalist “Still no mayflies”. Porritt’s discouragement of the collecting of mayflies must have played some part in the apparent lack of interest of the entomologists in the order. As a result the two decades after his death was the period of the greatest interest and activity in the Yorkshire mayflies. The Porritt Collection of Insects The Porritt Collection of Macro-Lepidoptera consists of 23,000 specimens housed in 71 cabinet drawers. His collection of Neuroptera (Mayflies, Dragonflies and Caddis flies) and Orthoptera (Earwigs, Grasshoppers, Crickets and Cockroaches) comprised 16,000 specimens housed in 65 cabinet drawers. The Lepidoptera collection was purchased by subscription and is now kept at the Tolson Memorial Museum in Huddersfield, together with the Neuroptera and Orthoptera collection which was his personal bequest; it does not however contain any mayflies. In 1925 the YNU set up a River Investigation Committee with monthly collecting from the Wharfe at Grassington and Harewood; collecting at Beckermonds, Ilkley and Ulleskelf was to be twice yearly. The first secretary of the Committee was C. A. Cheetham. In 1926, the names of J. R. Dibb and W. C. Hincks appear in the excursion reports in The Naturalist , and in 1929 came the first Fresh Water Biology Report, edited by J. M. Brown. This was followed by the First Ephemeroptera Report in 1932 and the names of several entomologists working on the order were acknowledged. In 1945 J. R. Dibb’s paper Yorkshire Mayflies or Ephemeroptera was published as part of the Transactions of the YNU. This list of 37 species recorded in Yorkshire covered all the vice-counties, although it is far from comprehensive in terms of distribution. It also included a bibliography and remains the basis for all later work. In 1945 H. Whitehead published additional records for 18 species and in 1946 J. R. Dibb published a short Addenda and Corrigenda to his 1945 paper. Between 1927 and 1947 was the period of the greatest activity and research in this field by members of the Union. The report produced jointly by Percival and Whitehead on the ecology of rivers belong to this period. In the following decades interest in fresh water biology declined and there were few active workers interested in the mayflies. During the 50 years which have elapsed, records of mayflies published in The Naturalist are sparse and the information of the YNU entomological record cards for the Ephemeroptera is indeed meagre. However, since the relaunching of the Fresh Water Biological Section of the YNU in 1989, many new records from all the vice-counties have been added and the distribution and life cycles of the less common upland species, e.g. Amelitus inopinatus and Siphlonurus lacustris, are becoming better known. 6 Yorkshire Mayflies My own interest in the mayflies goes back more than 60 years. I had an interest in fishing from an early age and was aware of the importance of the mayflies from The Compleat Angler. In 1928, 1 visited Bolton Abbey for the first time with a school party and persuaded an angler to show me the contents of his fly-wallet. I clearly remember the fine imitations of the Greendrake. After many years living in the north-east and other parts of the county I came to live quite close to the river at Pool-in- Wharfedale. Eric Thompson, who is still active in the Union and who had been a pupil of Whitehead, reminded me that much of the investigation work which had formed the basis of Percival and Whitehead’s report had been done on the Wharfe at Pool and Harewood. He suggested that I might wish to re-investigate the river fauna after an interval of 40 years because very little had been done in the meantime; moreover the Executive of the YNC had already approved the re- activation of the defunct Fresh Water Biological Section and the time might be opportune to attempt to do so. A further 23 years were to pass before the Section was reformed. Eric Thompson possessed several of Whitehead’s published papers and kindly gave them to me. There have been very few entomologists in the YNU studying the Yorkshire mayflies during that period. However, the predecessor of the Yorkshire Water Authority (YWA), the Ouse River Board, had partly financed the work of Percival and Whitehead and more extensive work had been done since 1956 by them and later by their successors the YWA. In 1967 the YWA began monitoring the invertebrates at 60 sites throughout the area of the county which they controlled, and by 1976 had carried out surveys at more than 1,000 sites. The sampling of invertebrates was encouraged by the Department of the Environment due to the growing awareness of the need for a biological classification of rivers as well as a chemical one. The Water Quality of Rivers The demand for pure water for potable and industrial use had increased rapidly after 1945 and the supplies of the impounded water from the upland reservoirs became inadequate, as was shown dramatically in 1959 when supplies in the Washburn Valley reservoirs failed and they virtually dried up. Additional supplies were sought and although some new reservoirs were built it was clear that new supplies would have to come (at least in the short term) from boreholes and river abstraction. The consequences of this have had profound effects on the flora and fauna and have created problems which are still far from being resolved. Rivers are more prone to pollution than reservoirs since pollution can be spread downstream. Chemical analysis is one method of assessing pollution but it was already well known that invertebrate sampling on a regular basis could be used to assess water quality and to determine short and long term changes in quality. The development of systems of classification of river quality by invertebrate sampling was encouraged by the authorities and a number of systems came into use. All are based on the presence or relative abundance of families of aquatic invertebrates, which are affected by differing degrees of organic pollution. The presence of these groups can be linked to a standard test of a water sample, the Biochemical (Biological) Oxygen Demand (BOD). Among the systems which have evolved are; Trent Biotic Index (Woodiwiss); Biotic Score (Chandler 1970); Biological Monitoring Working Part Score (BMWP). The latter is the one most widely used at the present time. The method is not complicated and in most cases it is not necessary to determine the invertebrates collected down to species. A score on a scale of 10 down to 1 is allotted to groups of invertebrates collected in a sample; mayflies, caddis flies and stoneflies mostly score 10; in the lowest groups are: some molluscs = 3, Chironmids = 2, all Oligochaeta = 1. The total score is added to produce an average score per taxa which can be directly related to a classification scale. A computer programme RIVPACS is also under development but at the present time it is not in general use. Since mayflies at some time of the year may account for as much as 20% of the biomass, they are an important integer in any invertebrate classification system. Yorkshire Mayflies 7 In the case of the Ephemeroptera the surveys are carried out entirely upon the nymphs and although if they are well developed most can be identified fairly easily down to species, there are problems in doing so in some families, e.g. Baetidae , particularly when they are very small. It is for this reason that one of the most abundant species on the Wharfe, The Pale Watery, Baetis fuscatus is not separated in the YWA lists. It is necessary to explain that the eggs hatch as larvae and are termed nymphs as they develop; they resemble fairly closely the adult and after a series of moults (instars) emerge to become the winged sub-imago (the angler’s Dun). The final metamorphosis is the imago (the angler’s Spinner). However, the distribution records of the YWA collated between 1971 and 1976 are probably the largest group of records of Yorkshire mayflies available at the present time and voucher specimens identified by various authorities have been retained. Work has slowed down during the past decade although some of the work is not done by the National Rivers Authority (NRA). The other large group of records is that of the author who has identified and recorded adult insects as well as nymphs. The collection of nymphs throughout the year is simple; it can be done at specific locations and at different seasons. The observation of adults is more difficult for the following reasons: 1 . Some species have a two year life cycle. 2. Some species are univoltine while others are bivoltine and this may vary in different years. 3. The emergence of the whole population of some species may occur in a very short period of time, so that records depend on the presence of the observer. 4. The period of emergence of the adults may take place over several weeks or even months and the numbers hatching may at times be quite small, e.g. Baetis spp. 5. Some species emerge at dusk or at dawn and the metamorphosis from sub-imago to imago is quite rapid, e.g. Caenis spp. 6. The adults are often difficult to locate in their shelter in high trees or even on bridges and buildings. 7. The populations of certain species are small and the duns emerge individually, e.g. Heptagenia sulphurea. 8. The less common species, which in Yorkshire are mainly confined to the uplands, appear to emerge over a very short period of time in good weather when the wind speed is low. It is clear that a naturalist studying the Ephemeroptera and living close to a large river system has considerable advantages over the casual observer. The method of sampling invertebrates is by disturbing the bed by a set number of standard ‘kicks’ and collecting the invertebrates in a net; after sorting, this produces a reasonably reliable indication of the biological quality of a river; it is less so for lakes, reservoirs and deep tidal stretches where there are physical limitations in sampling. In rivers, the statistical variations can be complex; surveying may be hindered by the topography and the season of sampling (although it is mainly confined to Spring, Summer and Autumn). The aquatic and marginal vegetation was not taken into account in the earlier surveys and the biological effects of augmentation, abstraction and inter-river transfers has only begun to be investigated in recent years. The Distribution of Ephemeroptera in Yorkshire The maps showing the water quality of Yorkshire rivers equate closely to the distribution maps of the riverine species of the Ephemeroptera in the county. Apart from some genera of the Caenidae and the Baetidae , the abundance of mayflies, stoneflies and most caddis- flies declines as the water quality deteriorates from Class 1 to Class 2. The higher levels of the rivers and their tributaries are swift flowing and mainly stony-bottomed and the invertebrate and vertebrate fauna are highly specialised. Mayflies also have a distinct preference for streams which have a pH value >7 although this may be directly related to the algae and microflora on which they feed. None of the British species are predators. The most ubiquitous species are the Baetidae ; one species, Baetis rhodani, called by 8 Yorkshire Mayflies anglers the Large Dark Olive, is found in every Yorkshire river system and is widespread throughout the British Isles. It may be seen on the wing in small numbers during every month of the year and occurs in such varied habitats as the calcareous rills which drain into Malham Tam to the deep slow-flowing waters of the Ouse. The stated periods during which the Ephemeroptera may be seen on the wing can be misleading; for instance, the peak hatch of B. rhodani in Yorkshire is during May and it appears to be univoltine in most years, being bivoltine in years when there is a prolonged drought and high water temperature. Pond and Lake Species Many of the upland reservoirs in Yorkshire have been created in steep-side narrow valleys and do not have large populations of mayflies; there are few natural lakes in Yorkshire but small ponds and disused gravel pits with macrophytes are likely habitats provided that they are not polluted. There are no British species which are only found in lakes and ponds, but certain species which are adapted to slow flowing rivers may be found in Stillwater and reservoirs, particularly those which are formed by damming streams. The large mayfly Ephemera danica is widely distributed throughout Yorkshire on calcareous rivers but as the nymphs are silt burrowers they tend to be absent from fast flowing, stony-bottomed rivers unless the habitat has been modified. Occasionally this occurs naturally when a stream becomes blocked and silt accumulates, but more often when a dam has been built across the river, allowing deep silt to build up along the banks. This is typical of the R. Nidd which has a large greendrake population upstream of the weirs. If the weirs are destroyed, the insects usually disappear from that reach of the river, as is known to have happened at Arthington on the R. Wharfe. On the little R. Dove in Douth waite Dale in North Yorkshire there is a large population of E. danica in deep silt washed down from the moors but this stream is calcareous and has a high pH value. A close relative, E. vulgata, the anglers’ Dark Mackerel, occurs in huge numbers in Swinsty Reservoir, in some adjacent reservoirs and in the Leeds/Liverpool Canal from Gargrave to the centre of Leeds. In the eastern side of the county it was once recorded from the Sea Cut at Scalby where its current status is not known. Its distribution is very local in England, occurring mainly in slow flowing rivers and meres in the west, but is spreading to man-made lakes and disused gravel pits in the Midlands and the south. E. vulgata was first recorded on the Leeds/Liverpool Canal at Gargrave in 1927 and in 1931 at Winterbum Reservoir which is a supply reservoir for the Canal. It is remarkable that its spread via the Canal was unnoticed by the entomologists, although swarms were pointed out to me at Esholt by a Bradford naturalist in 1952 under the name of E. danica. The sub-imagos frequently rest on barges during cool weather and travel many kilometres in this way. My investigations of its occurrence in Cheshire and Lancashire when I lived there would indicate that the canal is the obvious route by which the species came into Yorkshire. Two species of the Baetidae, Cloeon simile and Cloeon dipterum, the Pond and the Lake Oliver, have been recorded from Malham Tam. On the record cards at Malham and in the YNU Malham Reports only Cloeon simile is recorded, but during the two-day YNU excursion to Malham in May 1993, only nymphs and adults of Cloeon dipterum were found. Extensive surveys of the Tam were made from a boat during the excursion and a light trap was operated. Further surveys have not produced any specimens of C. simile; C. simile nymphs are usually found at a depth of c. 2 metres and have a preference as a habitat for the Water Milfoil Myriophyllum spicatum , which does occur in the Tam. It is interesting too that C. dipterum is the only European mayfly which is ovi-viviparous; the female rests 10 to 12 days before returning to the water to oviposition, when the eggs hatch immediately on contact with the water. I have only once located resting, fertilised females. 25 Years of Studying The Yorkshire Mayflies The author’s approach was first to attempt to determine what changes, if any, in the 9 Yorkshire Mayflies distribution and abundance of mayflies had taken place in the intervening years since Percival and Whitehead published their 1930 report. Fortunately, the exact dates of the surveys are given in the reports, making comparisons fairly reliable. The list of mayfly species recorded at Pool was unchanged but pollution from industry, agriculture and sewage was on a scale much greater than that noted at Pool Bridge between 1928/1930. The comparison of the abundance of the populations was more difficult but it was possible to make biological classification comparisons for some stations. In 1968 the river declined to class 2 downstream of Pool Bridge and mayflies declined in numbers towards the tidal reaches. Feeding Dippers are a good indicator of the presence of mayflies; they are not often seen downstream of Arthington Viaduct. In subsequent years, in spite of the improvements in sewage treatment, the quality did not improve dramatically and the industrial pollution was a source of concern. The maps showing the water quality of Yorkshire rivers between 1968 and 1994 equate closely to the distribution of mayflies. The Macrophytes The most noticeable change over the next 15 years was in the reduction in the river vegetation of the Wharfe. Limited information on the distribution of the macrophytes of Yorkshire rivers over the past 120 years may be obtained from the Transactions of the YNU and the Floras of F. A. Lees, W. G. Baker and J. F. Robinson. A more recent survey of the Wharfe was that of R. W. Butcher in 1933; this indicated for example, that the Water crowfoot Ranunculus fluitans was dominant in the swift portions and frequent in the slower portions. This plant does not occur on the Wharfe today and may be extinct in Yorkshire. The Water Crowfoot R. penicillatus subsp. pseudofluitans, which had been a feature of the river, had decreased since the 1930s and had become virtually extinct upstream of Pool. The presence of macrophytes plays an important role in the abundance of invertebrates in any river system, resulting in some authors giving a pollution tolerance relating to groups of British macrophytes. Replanting of R. penicillatus subsp. pseudofluitans has been taking place systematically in the Wharfe from Grassington down to Hare wood Bridge since 1990 and the plant is becoming re-established in well oxygenated parts of the river. The reappearance in huge numbers of a caddis fly Brachycentrus subnubilus on the mid- Wharfe is believed to be in part due to the increase of some macrophytes in recent years. Although the increase in macrophytes in some rivers is due to eutrophication, the presence of the mayflies in some numbers (except Baetis rhodani) does usually indicate good quality. Current Research on the Ephemetoptera The Fresh Water Biological Association published its first key to the Ephemeroptera by D. E. Kimmins in 1942, followed by a separate key to the larvae in 1961. Since the first publication there has been a growing interest in the order in Europe and in America, which has resulted in a large number of published references. There have also been several International Ephemeroptera Conferences. There are few aspects of the life cycle which have not now been studied. We now know that of the 48 British species, 30 occur mainly in running water and 18 in both running and standing waters. In spite of the intensive work on individual species both in the field and in the laboratory, there are some aspects of the life cycles or behaviour which have not been resolved and the author has kept observations on a number of species which are common or locally common and over whose habits there is a question mark. Oviposition The method of oviposition varies: some Yorkshire species enter the water to deposit their eggs on stones, e.g. Baetis rhodani. Although this is well documented I have not found it easy to observe on large rivers, and the females do dip the abdomen while flying upstream. It has been suggested that the purpose is to moisten the eggs. (There is a parallel with a British caddis fly Brachycentrus subnubilus which dips but ovipositions under water.) 10 Yorkshire Mayflies Baetis fuscatus hatches in huge numbers on the Wharfe and the Ure with a peak between the end of May and mid-June. It is estimated that 90% of the nymphs emerge during this period. The triggering factor appears to be a combination of light intensity, high barometric pressure, low water flow and light wind speed. During the period of emergence, birds, fish and bats feed intensively upon both the nymphs and the winged adults. After swarming and mating the females fly upstream and oviposition by dipping in the surface film, usually in water 0.5 to 1 metre deep, but avoid ‘broken water’. Although I have never seen winged adults of this species entering the water, other observers claim to have done so. It is possible that experiments with artificial streams may give rise to variations in behaviour. Ephemera vulgata In Yorkshire and elsewhere the eggs are deposited on warm days when there is very little wind. The usual time is during the afternoon but when the weather has been windy during the preceding days, followed by a calm day, very large numbers of females will leave the surrounding trees from as early as 7 a.m. and ovipositioning may continue throughout the day until evening. On such days swarms of males may be seen flying close to a marker; dam walls, buildings and dead trees are typical sites and are always close to the area where ovipositioning will take place. The same sites have been noted for over a period of 20 years. The areas selected for ovipositioning are the same areas where the nymphs have passed the previous two years in their burrows. These areas follow the course of streams which were submerged when the reservoirs were built and through which currents of water flow from the connecting feeders. At normal water levels it is not possible to capture nymphs but in drought years it is possible to examine the sites and to count the number of burrows per square metre. Downstream Drift and Migration There is a downstream drift and some upstream movement of nymphs in rivers and streams. Some of this voluntary but very large numbers of invertebrates are washed out during periods of heavy flooding, particularly on the spate rivers; macrophytes are tom out and may be deposited to regenerate successfully downstream; in some severe floods more than 50% of the beds of aquatic mosses such as those found on the extended base of Harewood Bridge may be completely washed away and even be deposited in adjoining fields. The larvae and the over-wintering eggs of one of the most abundant species of mayfly Ephemerella ignita (the anglers’ Blue-winged Olive) occur in millions in some of the beds of aquatic mosses, particularly Eurhynchium rusciforme. Those species whose eggs overwinter or whose larvae do not develop during the winter would therefore appear to be most vulnerable to loss of habitat. The adult mayflies whose nymphs are burrowers (Ephemera) do not travel very far from the point of emergence. The adults of the Baetidae and Ephemerellidae certainly do fly long distances (up to 1 km has been observed). In Yorkshire, this movement is mainly upstream, but downstream movement ‘in huge numbers’ in search of ‘broken water’ (indicating submerged vegetation) was described by the well known Test river keeper, A. J. Lunn. At Castley on the Wharfe and elsewhere, E. ignita has been known to leave the river and follow nearby roads for more than 1 km and oviposition on the damp road surface and upon parked motor vehicles. This behaviour has been noted towards dusk after rain, when the river is running high; no doubt the road surface with pools is mistaken for ‘broken water’ as observed by L. Magee over the period 1970-1990. Published references do suggest that upstream migration is minimal; the author’s observation is that this is true for the species which are least vulnerable to disturbance, e.g. species with burrowing nymphs and those with stone-clinging nymphs. Colonisation Mayflies do colonise lakes but little has been published. They are known to have been 11 Yorkshire Mayflies introduced successfully by anglers into man-made lakes such as fish ponds and gravel pits, and have also colonised lakes and ponds close to rivers and canals ( Cleon dipterum can be found even in water butts). In 1991 Ephemera vulgata was seen emerging in a moorland pond which had been formed in 1989 by damming a small stream. This pond was 8 km from the nearest known colony and the owner was adamant that no insects or animals had been deliberately introduced. Eaton (1883-88) quotes examples of swarms seen at a height of 500 feet above the Rhine but most descriptions of mating flights in literature indicate a height of between 2 and 10m. Swarms of Baetis rhodani have been observed at a height of 15m, above tall trees adjacent to several Yorkshire rivers. Conclusions There have been few additions to the list of Yorkshire mayflies published by J. R. Dibb in the Transactions of the YNU in 1945 and it seems unlikely that many more will be added. Additional species found in Yorkshire in recent years are Heptagenia fuscogrisea and Caenis luctuosa (moesta). There are however a number of species for which there are few Yorkshire records but which may prove to be more widespread since they occur in neighbouring vice-counties. A Check List of Yorkshire Mayflies Anglers’ Name Status 1. Siphlonurus armatus Summer Mayfly Local, VC64. No recent records. 2. Siphlonurus lacustris Summer Mayfly Local, VC62, VC63, VC64, VC65 (Upland species). 3. Ameletus inopinatus Local, VC62, VC64, VC65. 4. Baetis rhodani Dark Olive Widespread in Yorkshire in rivers. 5. Baetis atrebatinus Dark Dun Rare. R. Swale. 6. Baetis fuse atus Pale Watery Abundant on some rivers in all vice-counties. 7. Baetis scambus Small Olive Widespread in rivers in all vice-counties. 8. Baetis vernus Medium Olive In all vice-counties but less common than B. scambus. 9. Baetis muticus Iron Blue Widespread in rivers in all vice-counties. 10. Centroptilum luteolum Little Sky Blue In all vice-counties but not on all main river systems. 11. Centroptilum pennulatum Blue-winged Pale Watery Local, VC62, VC63, VC64, VC65. 12. Cloeon dipterum Pond or Lake Olive In unpolluted ponds and lakes with aquatic vegetation. 13. Cloeon simile Pond or Lake Olive Local, VC64, VC65. 14. Procloeum bifidum Little Pale Blue VC62, VC62, VC63, VC64, VC65. 15. Rhithrogena semicolorata Yellow Upright Widespread in stony bottomed streams. 16. Heptagenia sulphurea Primrose Dun Local, main rivers in VC64, VC65. 12 17. Heptagenia fuscogrisea 18. Heptagenia lateralis 19. Ecdyonurus torrentis 20. Ecdyonurus venosus 21. Ecdyonurus dispar 22. Ecdyonurus insignis 23. Leptophlebia marginata 24. Leptophlebia vespertina 25. Habbrophlebia fusca 26. Paraleptophlebia submarginata 27. Paraleptophlebia cincta 28. Ephemera vulgata 29. Ephemera danica 30. Ephemerella ignita 31. Ephemerella notata 32. Brachycercus harrisella 33. Caenis macrura 34. Caenis luctuosa 35. Caenis horaria 36. Caenis rivulorum Yorkshire Mayflies Brown May Dun Dark Dun Brook Dun March brown August Dun Large Green Dun Sepia Dun Claret Dun Ditch Dun Turkey Brown Purple Dun Dark Mackerel Greendrake Blue-Winged Olive Yellow Evening Dun Anglers’ Curse Anglers’ Curse Anglers’ Curse Anglers’ Curse Only in R. Derwent, Driffield Beck and R. Hull. In lakes and rivers, local, VC62, VC64, VC65. In all vice-counties. Prefers stony bottomed streams. Widespread in unpolluted stony bottomed streams. In all vice-counties. Prefers stony bottomed streams. Local, R. Ribble, R. Wenning and R. Swale. Local, VC63, VC64 lakes and streams. Local, lakes and slow streams. Slow streams with vegetation, VC61, VC62, VC64, VC65. Small stony streams, VC62, VC64, VC65. Small stony rivers, VC62, VC64, VC65. Morehall Reservoir VC63, Leeds/Liverpool Canal VC63 and VC64; reservoirs in VC64. All vice-counties; lakes and rivers, chiefly slow- flowing. In fast flowing rivers in all vice-counties. Similar habitat to last species but much more local, VC64, VC65. Local on Ouse tributaries: Wharfe, Swale, Ure, Nidd and Pocklington Canal. Maybe under-recorded. Very local. Aire, Wharfe and Ure. Local, VC62, VC63, VC64. Local, VC63, VC64. Stony streams. Local, VC64, VC65. Note. Very large areas of Yorkshire are underworked and some old records are dubious. The checklist is therefore merely a guide to the verified Yorkshire species. Distribution maps for all species are in preparation. Book Reviews 13 Acknowledgements The author wishes to acknowledge the encouragement of E. Thompson who suggested the studies and for the gift of reports; A. Henderson for tracing obscure references: D. T. Richardson for microscopic examination of some species; members of the YNU for submitting records and biologists of the former Yorkshire Water Authority for details of unpublished invertebrate surveys. References Aelianus, Claudius (1784) De natura animalium. Libri xvii. Schneider, Leipzig. Aristotles, De partibus animalium 682 a 27. Berners, J. (1496) The Treatyse of Fysshinge wyth an Angle. Wynkyn de Worde, Westminster, London. Bratton, J. H. (1990) A review of the scarcer Ephemeroptera and Plecoptera of Great Britain. Research and Survey in Nature Conservancy No 29. Nature Conservancy Council, Peterborough. Butcher, R. W. (1933) Studies on the ecology of rivers. I On the distribution of macrophytic vegetation in the rivers of Britain. J. Ecol. 21: 58-91. Cluyt, Outgert (1634) Opuscula duo singularia. II. De Hemerobia sive Ephemero Insecto Majali verme. Amsterdam. Dibb, J. R. (1945) Yorkshire Mayflies or Ephemeroptera. Trans. Yorks. Nat. Un. 36(2): 1- 20. Eaton, A. E. (1883-88) A revisional monograph of recent Ephemeridae or Mayflies. Trans Linn. Soc., Zool., series 2, 3(1): 1-352. Hellawell, J. M. (1990) The Biological Surveillance of Rivers. Water Research Centre, Stevenage. Hofland, T. C. (1839) The British Anglers' Manual. Whitehead, London. Magee, L. (1994) Fly Fishing. The North Country Tradition. Smith Settle, Otley. Miall, L. C. (1903) The Natural History of Aquatic Insects. Macmillan, London. Mol, A. W. M. (1984) The Earliest Epoch in the Study of Mayflies ( Ephemeroptera ). Proceedings of the Fourth International Conference, Ephemeroptera, 3-9, CSAV, 1984. Percival, E. and Whitehead, H. (1930) Biological survey of the River Wharfe, II. Report on the invertebrate fauna. J. Ecol. 18: 286-302. Ronalds, A. (1836) The F ly fisher’ s Entomology. 10th edition. Longmans, London. Scaliger, J. C. (1557) Exotericarum exercitationum. Paris. Swammerdam, J. (1675) Ephemeri vitae. Haft of Oever-aas, Amsterdam. Theakston, M. (1853) A List of Natural Flies that are taken by Trout, Grayling and Smelt in the Streams ofRipon. W. Harrison, Ripon. Walton, Izaak (1653) The Compleat Angler. (2nd edition 1655). Marriott, London. BOOK REVIEWS The Badger Man: memoirs of a biologist by Ernest Neal. Pp. x + 274. with 22 black and white photographs and 6 cartoons. 1994. Providence Press, Ely, Cambridgeshire. £13.95 paperback. Ernest Neal is well known as the leading authority on the biology of our native badger. His reputation has been established through many years of study, publication of books and scientific papers, service on committees and advisory bodies and appearances on radio and television. This is the public image but only when reading his autobiography does one appreciate the much greater diversity of his contributions in what has been a rewarding life. The son of a Baptist minister, Ernest (bom in 1911) was the youngest of four children. While the family lived modestly, Ernest nevertheless experienced a diverse and rewarding childhood, being introduced to natural history through his father’s interest in butterflies. Completion of a degree course at London University, while posing few academic 14 Book Reviews difficulties, did throw up a number of financial problems which were only resolved by taking up junior teaching positions, undertaking odd jobs and attending evening classes at Chelsea Polytechnic. Throughout his memoir comes through a burning enthusiasm for natural history, not only of butterflies but equally of all plants and animals whether terrestrial or marine. His badger interests were, in fact, not initiated until he was established in his first teaching post at Rendcombe College. Ernest Neal’s prime professional commitment was to school teaching, first at Rendcombe and then at Taunton, where he served as Head of Science, Housemaster and Deputy Head. His dedication, wisdom and sincere interest in his boys constantly emerges. Even with these considerable responsibilities his commitment to natural history could not be submerged. More than that, he has undertaken fundamental research on the biology of the badger, particularly its reproduction, social behaviour and status which has been the foundation for much further study. How stimulating it must have been for his students to have had such a teacher. Photography and the media were among his other interests and it is through his anecdotes and vignettes of various episodes that the events of the past, many in the early days of natural history broadcasting, come to life. That Ernest Neal has lived a full and rewarding life bursts forth from this book. Teacher, author, scientist, administrator, photographer and broadcaster are among his many roles, while his geographical experience extends from Britain to much of Africa and Europe. His family connections, which feature prominently, have been deep and strong, initially through his parents and siblings and subsequently and for over fifty years through his wife Betty and their children. Equally strong is his religious commitment. He writes well, conveying his own enthusiasm, but is never assertive as to his own successes and contributions. The book is more than a good read, it is an example of considerable achievement (from time to time against a background of serious ill health) for which we are all the richer. MJD Flora Europaea. Volume 1: Psilotaceae to Platanaceae. Edited by T. G. Tutin et al. 2nd edition. Pp. xlvi + 581, including 5 maps. Cambridge University Press. 1993. £100.00. The first volume of this prestigious work, hailed on its first publication 30 years ago as a model of its kind for international use, has now been thoroughly revised and considerably extended to include a larger number of taxa, each of which is described with admirable clarity and conciseness. The original highly satisfactory format and style have been retained. It will be noted that its subtitle has necessarily been changed to accommodate the interesting discovery in south-west Spain of a ‘tropical and subtropical’ psilophyte, Psilotum nudum. All the useful features of the first edition are included, but the use of contrastingly coloured pages for easy cross-referencing of the Explanatory Notes and the Glossary of Technical Terms has been dropped, which is a pity: presumably the publishers felt that this was an unjustifiable luxury in an already unavoidably expensive volume. Flora Europaea is sponsored by the Linnean Society of London and the preparation of this new edition of Volume 1 has been supervised by an editorial committee based in Britain and Ireland which has coordinated a mass of data from international sources, much of it via an impressive body of experts; the appendices, for example, provide biographical and bibliographical information on more than 1300 botanists and their publications. Both editors and publishers are to be heartily congratulated on realising this monumental project, which will be enthusiastically welcomed throughout the botanical world. Sadly, however, it seems that at present some doubt hangs over the production of a revision of the remaining four volumes of this indispensable work. MRDS 15 OTTERS {LUTRA LUTRA L.) AS SCAVENGERS: AN EXPERIMENT RAY HEWSON Department of Zoology, University of Aberdeen, Tillydrone Avenue, Aberdeen AB9 2TN Introduction Salmon Salmo salar, spawning in the upper reaches of the River Dee and its tributaries in north-east Scotland in November and December, provide a potentially large supply of food for otters, either as prey or carrion. Otters readily take salmon in the shallow water at the spawning redds (Carss et al. 1990), in addition to which many salmon carcases are available to scavengers from fish that die after spawning. Only 3-6% of salmon that have spawned return to spawn a second time (Mills 1986). Thus salmon carrion provides an abundant seasonal food supply along the Dee, amounting to as much as 36 kg. km 1 along the river bank (Hewson 1995). This paper describes scavenging by otters based on an experiment in which radio-tagged salmon carcases were provided to determine the extent to which otters scavenge when live fish are readily available. Study Areas The study areas comprised 900 m of the Bum of Cattie from its junction with the river Dee, and 400m of the Beltie Bum, which joins the Dee 4.0 km downstream and 6.5 km downstream of the confluence of Dee and Cattie (Figure 1). Both are used by spawning salmon which travel several km further upstream to spawning redds. FIGURE 1 Study areas on River Dee; A Dinnet, B Blackhall. Streams used by spawning salmon; (1) Tarland, (2) Cattie, (3) Beltie, (4) Sheeoch. The Cattie is 4-5m wide, and 0.3 -1.0m deep, with riffles and pools, the bottom sandy or gravel-covered. Alder Alnus glutinosa and birch Betula spp. line the banks and fallen branches obstruct the flow of the stream and cause salmon carcases to lodge in them. The 400m of the Beltie bum is 3-4m wide, slow-moving and silt-bottomed. It is therefore unsuitable for spawning salmon which pass through to spawn in the upper reaches. The banks were steep and man-made during former drainage operations, and were Naturalist 120 (1995) 16 Otters (Lutra lutra L.) as Scavengers: an Experiment partially lined with willows Salix spp. Otters were common and fed largely upon brown trout Salmo trutta outside the spawning season of salmon when there was little other aquatic prey (Kruuk et al. 1993). Other scavengers, which occurred on both study areas and might have benefited from salmon carcases landed by otters included mink Mustela vison, fox Vulpes vulpes and various scavenging birds, heron Ardea cinerea , carrion crow Corvus corone, and moorhen Gallinula chloropus. Great black-backed gulls Larus marinus , which regularly scavenge salmon carcases along the Dee, did not forage along the tributary bums. Methods Twenty-three female salmon carcases, intact except for the stomach and part of the snout, were fitted with radio transmitters (Hewson 1995). Between 24 November 1992 and 10 March 1993, 14 of these were placed, two at a time, in shallow backwaters in the Cattie and two in the Dee nearby. They were replaced when scavenged or washed away by spates. Seven carcases were placed singly, and replaced when gone, on a small sandy spit at the water’s edge on the Beltie which regularly showed tracks of otters, and where otters had scavenged carcases in an earlier study (Hewson 1995). The spit was too small to accommodate two salmon and the adjacent stream narrow and shallow. Radio-tracking was carried at intervals of 1-3 days on the Cattie and 1-12 days on the Beltie. The remains of salmon killed or scavenged by otters were generally found within 2m of the water with a trail through the vegetation from the water’s edge and in some cases otter tracks in sand or mud. There was no attempt to conceal the carcase and otters did not seek secluded places to feed. Otters fed between the head and dorsal or belly fins of salmon carcases, sometimes biting through the spine or removing the carcase except for the head. Freshly killed fish showed blood and scattered scales. Of the other scavengers of salmon carcases, crow and great black-backed gulls were seen feeding at some of the experimental carcases. Crows have difficulty in breaking into salmon carcases and generally do so at the anus or by making small pits l-2cm in diameter and 1cm deep in rotting carcases. They remove the eyes from fresh carcases of various species often without further scavenging (Houston 1978, Hewson 1984, 1995). Great black-backed gulls tore large pieces from salmon carcases but left no diagnostic signs. Mink fed where an otter had already broken into a salmon carcase, sometimes extending the area by feeding to a depth of c. 1cm below the skin, and also at the head between eye socket and snout. Results Scavenging by otters Of the 16 radio-tagged carcases put into the Cattie and Dee six were washed away by spates (see below). Otters hauled out the remaining 10 and scavenged nine of them (Table 1). The tenth was scavenged by birds. TABLE 1 Scavenging of salmon carcases placed in water (Cattie bum) or at water’s edge (Beltie bum) Number of carcases Put in Removed by spates Hauled out Otter scavenged Fate unknown or other scavenger Cattie/Dee 16 6 10 9 1 Beltie 7 0 7 4 2 Otters (Lutra lutra L.) as Scavengers: an Experiment 17 All the carcases were found within 2m of the water or in the stream or river. Within a three-week period three carcases had been taken 20-30m upstream where they were scavenged on boulders and at the water’s edge. One of the two carcases in the Dee was scavenged at the water’s edge, the other on a groyne 2m upstream of where it had been put in. Both were fully scavenged. All seven carcases put out at the Beltie were moved by otters, which left tracks in the sand; they scavenged at least four of them (Table 1). They did not take carcases from the water to the nearest place on the bank as at Cattie presumably because the banks of the Beltie bum were steep and one bank was alongside a public road. Instead, salmon carcases were either taken to the mouth of a culvert beneath the road, 1 10m upstream from the spit where they had been placed, or to the far bank 95m downstream. Radios from two of the remaining three carcases were traced to the middle of an arable field 800m from the Beltie and a conifer plantation 1.0 km away respectively. They may have been taken there by foxes after otters had recovered them from the shallow water and silt which had covered them since they were put out. Foxes are known to remove salmon carcases from the bank before feeding on them (Cuthbert 1973, Hewson 1994). Carcases moved by spates (Table 2) were washed into deeper water or lodged beneath driftwood. They were not scavenged by otters. Four of the six were moved out of the study area. One of these was found, thought to be scavenged by great black-backed gulls, 6 km downstream of the study area. TABLE 2 Salmon carcases placed in Cattie bum and removed by spates Date put in Date of spate Observations 13 Dec. 19 Dec. Found 5 Feb., not scavenged 13 Dec. 19 Dec. not found in study area 19 Dec. 26 Dec. lodged beneath driftwood 27 Dec. 5 Jan. 6 km downstream bird scavenged 27 Dec. 15 Jan. in R. Dee, 1 1 Feb. 10 Jan. 15 Jan. not found TABLE 3 Salmon carcases moved by otters from Bum of Cattie Time Initial Amount (days) weight (kg) scavenged by otters (kg)* 2 2.04 1.36 fully scavenged 1 2.81 0.57 10 2.67 2.10 fully scavenged 8 2.16 1.16 3 1.96 >1.50 fully scavenged 12 3.07 1.53 2 2.07 1.59 fully scavenged * when found. Some carcases were further scavenged by otters later . 18 Otters (Lutra lutra L.) as Scavengers: an Experiment Otters fed substantially upon salmon carcases placed in the Cattie, some of which were hauled out and scavenged within three days (Table 3). Carss et al (1990) found that otters killing spawning salmon on the Bum of Sheeoch, another tributary of the Dee, took an average 975g as a single meal. These were larger fish than those used in the present study and feeding occurred chiefly behind the pectoral fins. On the smaller carcases used in this study scavenging occurred in the same area but extended further towards the tail; in fully scavenged carcases only the skull, vertebrae, tail and skin, weighing together about 0.6 kg, remained. Amounts scavenged by otters at Cattie (mean 1.40kg, range 0.57-2.10) were larger than at Sheeoch but fell within the same range, 0.29-2.08kg. At Sheeoch otters obtained most of their daily food requirements by catching one salmon from those readily available on the spawning redds. There was no spawning redd within the Cattie and Beltie study areas and with food less readily available otters ate more from each carcase and returned to some of them for further scavenging. If fully scavenged carcases at Beltie (Table 4) were assumed to weigh 0.6kg the average amount eaten by otters there, 1.35kg, was similar to Cattie. TABLE 4 Salmon carcases moved by otters at Beltie Time (days) Initial weight (kg) Amount scavenged by otters (kg)* 7 2.53 fully scavenged later 10-18 1.08 scavenged by fox later 3 2.44 fully scavenged later 2 1.84 0.97 1 2.70 0.64 1 1.73 scavenged by fox later 12-17 2.12 not found * when found: some carcases were scavenged by otters later. Live prey of otters along the Cattie Between 29 Nov. 92 and 5 Feb. 93 the remains of nine salmon were found along the Cattie. One, a small female on a gravel spit, was scavenged by a heron which was flushed from the carcase. The remaining eight had been put on the bank by otters (Table 5). Seven had been killed (fresh blood). The eighth was a salmon seen dead in the water two days earlier. From these salmon a full meal (c. 1 .4kg) or more had been taken; only the head remained of two fish. A similar amount (1.3kg) was scavenged subsequently, principally by otters. The remains of the heaviest fish killed by an otter, from which a meal had been taken, weighed 4.9kg, indicating a live weight of around 6 kg, near the upper limit for salmon brought ashore by otters. (The average weight of a female otter is 7kg (Chanin (1991)). Other scavengers of salmon carcases Otters help other scavenging mammals and birds by removing salmon to the bank and leaving them partly eaten. Six of the seven salmon killed (and one scavenged) by otters along the Cattie provided food for other scavengers (Table 5). Crows were involved in all cases, removing eyes or making small pits in flesh. A great black-backed gull scavenged a carcase on which mink and crows had already fed, but mink scavenged only one carcase and great black-backed gulls two. The experimental carcases hauled out by otters on Cattie also provided food for other scavengers. Mink scavenged three, taking between 7 1 g and 284g per day, when more than one mink may have been involved. Crows removed eyes from four carcases and, during a period of snow-lie, fed upon one which had lain on' the stream bank for 83 days. Tracks and droppings indicated that crows had fed along with mink at three carcases. Otters (Lutra lutra L.) as Scavengers: an Experiment 19 Scavenging of salmon carcases at the Beltie by foxes has already been discussed. On the Sheeoch, Cuthbert (1973) found substantial scavenging of dead salmon by badgers Meles meles and foxes, both of which removed carcases from the stream bank. The amounts taken by scavengers other than otters were usually small and there was no evidence of competition for salmon carrion between otters and other bird or mammal scavengers (Hewson 1995, this study). TABLE 5 Feeding on salmon killed (and one scavenged) by otters along Cattie 29 Nov. 92 to 5 Feb. 93 Date Killed or scavenged Weight (kg) when found Subsequent scavenger Amount eaten later (kg) 29 Nov scavenged 2.36 otter, crow 1.33 1 Dec killed 4.90 mink, crow, gull 12 Dec killed 3.80 crow 28 Dec killed 2.58 otter, crow 1.28 9 Jan killed head only crow 19 Jan killed 1.28 otter, crow, gull? 0.89 19 Jan killed 2.16 otter, crow 1.73 5 Feb killed head only none - Gull refers to great black-backed gull. Discussion Salmon, as prey or carrion, are clearly important to otters during the spawning season (Hewson 1995). On a 7.5 km stretch of the Dee (B on Fig. 1) the salmon carcases found during December and early January could have provided the entire food supply of one or two otters taking only a single meal from each carcase. However, the salmon carcases on a 9 km stretch 21 km upstream (A), with a more rapid flow and few tributaries used by spawning salmon, would not have sustained an otter even if it had scavenged them fully (Hewson 1995). This study shows that otters readily take salmon carrion even when live fish are available and easily taken after spawning. Otters returned to feed on salmon they had killed and fed upon earlier, and then ate amounts equivalent to the average otter’s meal as described by Carss et al (1990). They also ate similar amounts of carrion from the carcases provided experimentally. A tentative estimate of the food of otters on the Cattie during the study indicates that salmon carrion may have been their major food. Captive otters when hungry took dead fish in preference to live ones and slow-moving fish more readily than faster ones (Erlinge 1968). Wild otters presumably find salmon which have spawned (kelts), slow-moving in the backwaters which they frequent, an easy prey. Similarly, dead salmon lying in shallow water provide an easy source of food. Outside their spawning season large salmon are not a usual food of otters (Kruuk et al. 1993) although present in the Dee as fresh-run fish from February onwards, presumably because these are more difficult to catch than smaller prey. In Ireland, O’Sullivan et al (1992) record sporadic otter scavenging of brown trout Salmo trutta L., sheep, cooked shrimps, Crangon vulgaris L. and domestic geese and fowls. Food remains on islands frequented by otters at Loch Park in north-east Scotland included brown hare Lepus europeaus, mallard Anas platyrhynchos, moorhen, woodpigeon Columba palumbus and pheasant Phasianus colchicus, all of which were probably scavenged rather than killed (Hewson 1973). Scavenging of salmon carcases during the spawning season provides a substantial part of the otter’s diet. At other times otters scavenge sporadically. 20 Book Review Acknowledgements I am grateful to Anneke Stolte for help in the field, to Dr H. Kruuk for helpful discussions, to J. Morris, (I.T.E. Banchory) for technical assistance, and to landowners on whose ground I worked. The Vincent Wildlife Trust made a grant towards the cost of the work, and the Freshwater Fisheries Laboratory, Pitlochry, provided the salmon carcases. G. Woodroffe made helpful comments on earlier drafts. References Carss, D. N., Kruuk, H. and Conroy, J. W. H. (1990) Predation on adult Atlantic salmon, Salmo salar L. by otters, Lutra lutra (L), within the River Dee system, Aberdeenshire, Scotland. J. Fish Biol. 37: 935-944. Chanin, P. (1991) Otter. In: The Handbook of British Mammals, ed. G. B. Corbet & S. Harris) pp. 424-431. Oxford, Blackwell. Cuthbert, J. H. (1973) Some observations on scavenging of salmon Salmo salar carrion. Western Naturalist 2: 72-74. Erlinge, S. (1968) Food studies on captive otters Lutra lutra L. Oikos 19: 259-270. Hewson, R. (1973) Food and feeding habits of Otters Lutra lutra at Loch Park, north-east Scotland .J.Zool. 170: 159-162. Hewson, R. (1984) Scavenging and predation upon sheep and lambs in west Scotland. J.appl.Ecol. 21:843-868. Hewson, R. (1985) Scavenging of salmon carcases by birds. Scottish Birds 13: 179-182. Hewson, R. (1995) Use of salmonid carcases by vertebrate scavengers. J. Zool. 235: 53-65. Houston, D. C. (1978) The motivation for hooded crow ( Corvus corone ) attacks on young lambs. Proc. Assoc. Appl. Biol. 88: 339-341. Kruuk, H., Carss, D. N., Conroy, J. W. H. and Durbin, L. (1993) Otter (Lutra lutra L.) numbers and fish productivity in two rivers in North-east Scotland. Symp. zool. Soc. Lond. 65: 171-191. O’Sullivan, W. M., Sleeman, D. A. & Murphy, D. M. (1992) Otters Lutra lutra feeding on carrion. Ir. Nat. J. 24: 140-143. Mills, D. H. (1986) The biology of Scottish salmon. In: The Status of Atlantic Salmon in Scotland (ed. D. Jenkins), pp. 10-19. ITE symposium No. 15, Huntingdon. BOOK REVIEW Flora of Radnorshire by R. G. Woods. Pp. xiii + 292, together with 9 pages of colour plates. National Museum of Wales, in association with the Bentham-Moxon Trust. 1993. £28.00 hardback. This work maintains the traditionally high standards of county Floras and is a testimony to Ray Woods’ detailed researches in mid-Wales over the past twenty years. Radnorshire is only one of several counties whose botany he has extensively explored, covering not only its vascular plants, but also its cryptogams; his ecological and conservation interests are also evident in this Flora. Chapters are provided on the county’s physical environment, plant communities (including a conspectus of their phytosociological classification), biogeography, changing flora, conservation and history of plant recording. The main body of the text provides ecological notes and locality details (maps on a tetrad basis given for the more widespread species) of flowering plants, ferns, mosses, liverworts and lichens; shorter sections deal with algae and cyanobacteria, and rust and smut fungi. The volume is well produced, the text being admirably supported by maps, tables, line drawings and colour photographs of habitats. Thanks to the generosity of its several sponsors, the Flora is extremely reasonably priced. MRDS 21 ACULEATE WASPS AND BEES (HYMENOPTERA: ACULEATA) OF BLAXTON COMMON IN WATSONIAN YORKSHIRE WITH THE INTRODUCTION OF A NEW NATIONAL QUALITY SCORING SYSTEM MICHAEL E. ARCHER Blaxton Common has been found to be an excellent locality for aculeate wasps and bees, having 123 recorded species, six species of national importance and ten species of regional significance. The Common, an area of about 150ha, is situated to the north-east of Blaxton, near Doncaster (VC63, SE6901). The region has sandy acid soils worked by the sand and gravel extraction industry. After sand extraction, dry open horizontal sand and small sandy clifflets are left. Vegetation has invaded the open spaces, leading to the development of birch and oak woodland. Sheltered by the woodland the open areas become important nesting and foraging resources for the aculeate wasps and bees. Continued growth of the birch and oak will eventually shade out the open areas but at present many open areas are present. Between 1980 and 1993, 17 visits were made to a sample area, about 25ha, of Blaxton Common along either side of the road from Finningly to Wroot. These visits were distributed throughout the year as follows: April (2 visits). May (4), June (3), July (3), August (3), September (2). During these three-hour visits all species of aculeate wasps and bees seen were recorded (Archer sample) and usually collected with a hand net for identification. In addition, I have had access to a small number of records from H. H. Corbett (June 1918), E. W. Aubrook (June 1969) and P. Skidmore (April 1967), a larger number of records from J. D. Coldwell (August 1991) and J. T. Bum (1972-78), to whom I am most grateful. In the following account biological names are according to Kloet and Hincks (1978). Results Species present at Blaxton Common At the family level. Table 1 shows the taxonomic distribution. The 122 recorded species represent about 46% of the aculeate wasps and bees recorded from Watsonian Yorkshire. In addition, J. T. Bum recorded the dryinid wasp Anteon jurineanum during May 1980. The Archer sample of solitary wasps and bees consists of 3 1 5 records derived from 9 1 species (Table 2). Fifty-eight species (63.7%) were recorded on one, two or three days (unusual species) while the other 33 species (36.3%) were recorded on from four to 15 days (common species) (Table 3). Solitary bee species are more equally represented in the common (21 species) and unusual (27) groups compared with the wasp species which are represented more in the unusual (31) than the common (12) groups of species. Thus solitary wasps species would seem to be more difficult to find than solitary bee species. With 29 species (31.9%) only being found on one visit, the recording of further species is very likely. A further eighteen solitary species have been recorded as follows: Dipogon subintermedius ( =D . nitidus), Anoplius nigerrimus, Ancistrocerus gazella, Tacky sphex unicolor, Trypoxylon attenuatum, Crabro peltarius, Crossocerus cetratus, C. megacephalus, Ectemnius cavifrons, E. cephalotes, Stigmus solskyi, Pemphredon inornatus, Diodontus luperus, Nysson dimidiatus, N. spinosus , N. trimaculatus, Argogorytes mystaceus, Andrena cineraria. Seventeen of these 18 species not found in the Archer sample are wasps species, indicating again the smaller probability of finding the wasp compared with the bee species. The following ant, social wasp, and bee species have been recorded: Formicidae: Myrmica ruginodes, Formica fusca , Lasius niger, Vespidae: Dolichovespula sylvestris, Vespula rufa, Paravespula germanica, P. vulgaris : Apidae: Bombus lucorum, B. terrestris. Naturalist 120 (1995) 22 Aculeate Wasps and Bees (Hymenoptera: Aculeata) ofBlaxton Common B. lapidarius , B. pratorum , B. hortorum , pascuorum, Psithyrus bohemicus , F\ vestalis , mellifera. Seasonal progression of solitary species From the Archer sample the solitary wasp species were only recorded during the summer months (Table 4). August was the most productive month for the number of species and individuals, and June, the month when the solitary wasp species first emerged, the best month for recording new species. The subterranean nesting species of the open sandy areas were very evident including the spider-hunting Pompilus cinereus , the caterpillar-hunting sand-wasp Ammophila sabulosa, the fly-hunting Crossocerus quadrimaculatus , the grasshopper-hunting Tachysphex pompiliformis and Evagetes crassicornis which is a cleptoparasite on other spider-hunting wasps. TABLE 1 The number of species of aculeate wasps and bees recorded from Blaxton Common No. species Solitary wasps Chrysididae 4 Mutillidae 1 Pompilidae 12 Eumenidae 3 Sphecidae 40 Total solitary wasps 60 Solitary bees Colletidae 6 Andrenidae 17 Halictidae 15 Megachilidae 3 Anthophoridae 8 Total solitary bees 49 Total solitary wasps & bees 109 Social wasps & bees Vespidae 4 Apidae 9 Total social wasps & bees 13 TABLE 2 The number of records and species of solitary wasps and bees recorded from Blaxton Common in the Archer sample Family No. species No. records Chrysididae 4 11 Mutillidae 1 4 Pompilidae 10 36 Eumenidae 2 2 Sphecidae 26 65 Collectidae 6 8 Andrenidae 16 94 Halictidae 15 62 Megachilidae 3 6 Anthophoridae 8 27 Aculeate Wasps and Bees ( Hymenoptera : Aculeata) ofBlaxton Common 23 TABLE 3 The number of days on which each species of solitary wasp and bee was recorded at B lax ton Common in the Archer sample No. records No. days Species No. species 29 1 Chrysis angustula , Priocnemis schioedtei, Ancistrocerus parietinus, A. trifasciatus, Trypoxylon clavicerum, Crabro cribrarius* , Crossocerus tarsatus , C. nigritus, Psen lutarius, Psenulus pallipes, Pemphredon lethifer , Diodontus minutus*, D. tristis *, Passaloecus gracilis , P. singulars, Gorytes quadrifasciatus, G. tumidus, Colletes daviesanus, C. succinctus *, Hylaeus communis , H. confusus , H .brevicornis , Andrena angustior , A. barbilabris*, Halictus rubicundus, H. tumulorum, Lasioglossum fratellum, L. punctatissimum , Megachile circumcincta. 29 34 2 Hedychridium ardens*, Arachnospila anceps, A. trivalis, Anoplius concinnus, Episyron rufipes , Trypoxylon figulus, Crossocerus palmipes , C. wesmaeli, Psen dahlbomi , Pemphredon lugubris, Andrena saundersella, A. varians , Lasioglossum nitidiusculum , Megachile versicolor , Nomada fabriciana, N. ruficornis, N. rufipes *. 17 36 3 Chrysis impressa, Priocnemis exaltata, Arachnospila spissa, Ectemnius continuus, Colletes fodiens, Andrena denticulata*, A. praecox, Lasiogalossum leucopum, Sphecodes gibbus. Megachile willughbiella, Nomada flavoguttata , Epeolus variegatus. 12 36 4 Myrmosa atra , Anoplius viaticus *, Crossocerus ovalis , Entomognathus brevis , Oxybelus uniglumis*, Mellinus arvensis*, Lasioglossum leucozonium, Sphecodes puncticeps , Nomada goodeniana. 9 35 5 Trichrysis cyanea, Andrena clarkella *, A.fulva , A. tibialis, Lasioglossum rufitarse, L. villosulum , Nomada leucophthalma*. 7 18 6 Lasioglossum calceatum, Sphecodes pellucidus*, Nomada marshamella. 3 7 7 Tachysphex pompiliformis*. 1 48 8 Evagetes crassicornis, Crossocerus quadrimaculatus , Ammophila sabulosa*, Andrena chrysosceles, A. scotica, A. subopaca. 6 36 9 Pompilus cine reus*, Andrena haemorrhoa, A. nigroaenea, Sphecodes monilicornis. 4 10 10 Andrena bicolor. 1 11 1 1 Sphecodes fasciatus. 1 15 15 Andrena minutula. 1 * Local species in Watsonian Yorkshire. From the Archer sample, the solitary bee species were recorded during the spring and summer months, being more frequent during the spring months (Table 4). May (for the 24 Aculeate Wasps and Bees (Hymenoptera: Aculeata) ofBlaxton Common spring species) and August (for the summer species) were the most productive months for the number of species and individuals. The number of new species was most frequent during the first month of emergence: April for the spring species and June for the summer species. Typical spring species were the mining bees, Andrena, with their cleptoparasites, Nomada, e.g. A. haemorrhoa with N. ruficornis and A. nigroaenea with N. goodeniana. Typical summer species were the mining bees, e.g. Colletes fodiens with its cleptoparasite Epeolus variegatus , Andrena denticulata with Nomada rufipes, Lasioglossum villosulum with Sphecodes puncticeps and the aerial nesting Megachile willughbiella. Some bee species were found in the spring and the summer having passed through two generations, e.g. Andrena minutula with Nomada flavoguttata , A. bicolor with N. fabriciana and Lasioglossum calceatum with Sphecodes monilicornis . TABLE 4 The number of species, new species and individuals of solitary wasps and bees recorded per month at Blaxton Common from the Archer sample April May June July August September Wasps No. species 0 0 19 20 32 7 No. new species 0 0 19 9 15 0 No. individuals 0 0 28 31 50 9 Bees No. species 22 24 21 11 17 13 No. new species 22 6 8 4 6 2 No. individuals 32 56 32 24 31 22 Quality Assessment of Solitary Species Six species are nationally scarce species (Falk, 1991). One species, Andrena tibialis , which is a category A scarce species, reaches the northern boundary of its British distribution in Watsonian Yorkshire. The other five species, which are category B scarce species, are either at the northern boundary of their distribution ( Priocnemis schioedtei, Nysson trimaculatus, Andrena varians) or are more widespread in Britain ( Crossocerus palmipes, Nysson dimidiatus). No nationally rare species (Falk, 1991) have been found. Ten species are rare in the context of Watsonian Yorkshire (Archer, 1993) ( Episyron rufipes, , Tachysphex unicolor, Crossocerus palmipes, Psen lutarius, Diodontus luperus, Nysson dimidiatus, N. trimaculatus, Hylaeus brevicornis, Andrena tibialis, Sphecodes puncticeps). There are 27 species of solitary wasps and bees, which although not rare in Watsonian Yorkshire, have a local distribution, being more or less restricted to sandy habitats (Archer, 1994a). Eighteen of these local species are found at Blaxton Common and except for C. peltarius are indicated in Table 3. The 109 species of solitary wasps and bees can be considered to have a common, frequent, occasional or rare status in Watsonian Yorkshire (Archer, 1993) (Table 5). By giving each species a score depending on the above statuses, including a higher score for the nationally scarce species, a quality score of 341 can be calculated (Table 6). Dividing the quality score by the 109 species gives a species quality score of 3.1. Ball (1992) proposed a status category scheme for invertebrates in a national context (Table 7). Since such a status coding has not previously been applied solely to the aculeate Hymenoptera of a particular locality the following proposals can be made. The nationally rare and scarce statuses will remain the same as previously considered. The regionally notable species are equated with the regionally rare species. Ball (1993, pers. comm.) defined the term “local” as a species either restricted to a particular habitat type or to a particular geographical area, or to widespread species which are intermediate in status Aculeate Wasps and Bees (Hymenoptera: Aculeata) of Blaxton Common 25 between common and scarce species. At present there is no objective way of assigning a common or local status to the species of the British aculeate Hymenoptera. From personal experience I have therefore assigned common or local status based upon abundance and distribution within England and Wales. Ireland was excluded as little information is available on Irish distributions, as were the Channel Islands, since their fauna relates more to France than to the British Isles, and Scotland, because its cooler climate has a profound effect in reducing the diversity of aculeate Hymenoptera. Using the Ball national status scheme a quality score of 209 and a species quality score of 1 .9 can be calculated (Table 7). TABLE 5 The regional coding of the 109 species of solitary wasps and bees recorded from Blaxton Common Status No. species Common 42 Frequent 34 Occasional 23 Rare 10 TABLE 6 The regional quality score of the species of solitary wasps and bees recorded at Blaxton Common Status Status Score No. species Quality Score (A) (B) (A*B) Common 1 41 41 Frequent 2 34 68 Occasional 4 22 88 Rare 8 6 48 Nationally Scarce 16 6 96 TABLE 7 The Ball national quality score of the species of solitary wasps and bees recorded at Blaxton Common Status Status Score No. species Quality Score (A) (B) (A*B) Common 1 65 65 Local 2 32 64 Regionally notable 4 6 24 Scarce B 8 5 40 Scarce A 16 1 16 Two objections can be raised against the Ball national status scheme. Firstly, since regionally notable species are unknown for many parts of England, Ball’s scheme cannot be applied. Secondly logically a national scheme should give a species status based upon that species’ importance in a national and larger geographical setting but not in a smaller or regional distribution. To overcome the above objections I suggest the following scheme in which the statuses of “Common” “Local” and “Regionally Notable” of Ball are replaced by: “Universal” “Widespread” and “Restricted”. These new statuses are assigned from personal experience of a species’ abundance and distribution within England and Wales. Universal species would be common species found throughout England and Wales, which usually extend into 26 Aculeate Wasps and Bees (Hymenoptera: Aculeata) ofBlaxton Common Scotland. Widespread species would be found in about three-quarters of England and Wales, usually with a distribution in Wales, southern and midland England or in northern and western England and Wales. Widespread species also may be found throughout England and Wales but either with a local distribution or a less than common abundance. Restricted species would mainly be found in about one-half of England and Wales, usually confined to southern England and East Anglia. Using this new national status scheme, a quality score of 205 (Table 8) and a species quality score of 1.9 can be calculated for Blaxton Common. Cleptoparasitic Load The cleptoparasitc load (CL) is the percentage of aculeate species that are cleptoparasites on other host aculeates (Table 9). At Blaxton Common the CL for the species of solitary bees is higher than the CL for the species of solitary wasps. Aerial Nester Frequency The aerial nester frequency (AF) is the percentage of host aculeate species that have aerial nest sites. Aerial nests are often in old beetle burrows in dead wood or the central cavities of stems such as those of bramble. Subterranean nesters nest in the soil, usually in burrows dug by themselves but sometimes in crevices or pre-formed burrows (Table 10). The AF for the species of solitary wasps is higher than the AF for the species of solitary bees at Blaxton Common. TABLE 8 The Archer national quality score of the species of solitary wasps and bees recorded at Blaxton Common Status Status Score (A) No. species (B) Quality Score (A*B) Universal 1 59 59 Widespread 2 43 86 Restricted 4 1 4 Scarce B 8 5 40 Scarce A 16 1 16 TABLE 9 The relative frequency of the cleptoparasitic species among the solitary wasps and bees from Blaxton Common No. No. Cleptoparasitic hosts cleptoparasites Load (H) (C) CL= 1 00*C/(H+C) Solitary Wasps 51 9 15.0 Solitary Bees 36 13 26.5 TABLE 10 The nesting habits of the host solitary wasp and bee species from Blaxton Common No. aerial No. subterranean Aerial nester nesters nesters frequency (A) (B) AF= 1 00* A/( A+S) Solitary Wasps 22 29 43.1 Solitary Bees 5 31 13.9 TABLE 1 1 A comparison of the quality scores of sandy habitats in Watsonian Yorkshire and elsewhere in England based on the species of solitary wasps and bees. Aculeate Wasps and Bees (Hymenoptera: Aculeata) ofBlaxton Common 27 o £ e .& £ M o 00 u ^ Os 2 ^"03 rr, 3! fa Ui 3! .2 a ft :* W) S3 O fa 06 PQ fa £ .2 .2 1 O c/3 & V, fa 5 £ C/3 " >. <30 .fa .2 -fa '£ § g. a « o © fa w £ <3 g-g fa fa < 03