BIOLOGICAL RECORDS - SOME NOTES ON TWITCHERS, SPLITTERS, LUMPERS AND APHIDS G . D . HEATHCOTE
Greenfly, I find it hard to see, Why God, Who made the Rose, Madethee. A. P. Herbert. All natural history studies can be said to add to the sum of human knowledge. However, most are made for no other reason than that the work gives interest and pleasure to the worker concerned, and not in the hope that he or she will make a major discovery or develop a theory of fundamental importance. There are, for example, the equivalent of the 'twitchers' of the bird world (i.e. those bird watchers who will travel long distances to see an uncommon bird, however briefly, to add it to their list of 'sightings') in most groups of naturalists, including entomologists. For some, making a list of species is seen as an end in itself, and this is rather like stamp collecting, but is there any scientific value in such lists and should they be published in these Transactions? I am sure that I am not alone in finding long lists of species, with equally long scientific names, very boring, but I hope to establish that there is a real need to correctly identify and record the distribution of plants and animals in Suffolk for the benefit of other naturalists. No matter what animal or plant is being studied it is helpful, and often essential to know what other animals and plants are living in the study area. Plants and animals do not live in isolation and their inter-relationships can be complex. To illustrate this, a case can be made to show that the number of old ladies living in a village will affect the amount of honey produced locally. It goes like this:'Old ladies keep cats - cats eat mice - mice destroy bumble bees' nests bumble bees pollinate flowers - flowers produce pollen and nectar - bees collect pollen and nectar to make honey Q.E.D. We usually have to rely upon others to identify and record the distribution of most of the species in our study areas, i.e. fall back on lists and distribution maps, and a major difficulty soon becomes obvious to anyone doing so. Lists and distribution maps reflect the distribution of the specialists interested in those particular groups. Species may be common in an area which is blank on a distribution map. We must also accept that a list of species is never complete, but it may still be useful, provided the identifications are correct. Several unrelated species may be adapted to a particular habitat in the same way (by 'parallel evolution') but may still differ in several important respects;
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confusion can be caused if they are not identified correctly. Correct identification can be even more important when closely related and morphologically identical species ('sibling species') are ecologically separate. For example, some blackfly of the 'Aphisfabae group' will feed on broad beans and not on Nasturtium (Tropaeolum majus) while others, apparently identical in form, produce few offspring and die prematurely on beans and multiply on Nasturtium. It is in an attempt to reduce this confusion that scientific rather than common or local names are given for plants and animals when it is important to establish their identity. For example, 'fulfer' or 'dow fulfer' were the names given by East Anglians to the thrush more familiar to most of us the Fieldfare, which is known scientifically as Tarduspilaris L., but these 'local' names would mean little to a Japanese ornithologist. Neither would I know the Japanese local names for T. pilaris, incidentally, but I would recognise the Latin name in an ornithological work otherwise written in Japanese characters. The 'double barreled' scientific name (genus and species) is usually printed in italics to make it more obvious in the text, whereas the abbreviated name that often follows, that of the 'authority' who 'invented' the species' name, is not. In the above example 'L.' is the abbreviated name of C. von Linne ('Linnaeus') (1707-1778) the famous Swedish naturalist. If we accept that there is some value in Publishing lists of species found in an area, most of usfindthem more interesting and useful if additional information is given, particularly the numbers found at a specific time. A species may be regarded as 'common' in one location in certain years, or months, but be distinctly 'uncommon' or even absent in others. For example, the Waxwing, Ampelis garrulus (L.), is an irregulär visitor to Suffolk, but there are occasional 'irruptions' when scattered flocks of these birds arrive during the winter months. Only once in 23 years have I seen Waxwings in my garden (eating Cotoneaster berries) and there were then seven of them. It is therefore important to record the common species - they may not be common in years to come, or may not have been so in the past. There are particular difficulties in recording the numbers and distribution of the more obscure groups of plants or animals in an area like Suffolk where there will be few naturalists studying them. I was interested professionally in a large group of insects, the aphids, which are all too familiar to most of us but which are difficult to identify and are poorly 'recorded' in Suffolk. They can therefore be considered an obscure group of insects, although aphids ('greenfly' and 'blackfly') are of great economic importance, not only because of the damage they do when feeding but because they spread many virus diseases in crop plants. Aphid species have very different life histories and feed on different plants but they may differ morphologically only in details such as the relative length of various joints of the antennae or legs, or on the number of hairs on the tail (cauda). There is no one book which can be used to identify all British aphids, although those of economic importance can be recognised from Blackman and Eastop's Aphids on the world's crop (1984), which also gives summaries of what is known of each species. Aphids are particularly difficult to identify because the same species occurs in many different forms. Individuais may be wingless (and are then known as Trans. Suffolk Nat. Soc. 22
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'apterae'), or winged ('alatae'), and those which hatch from eggs (Jundatrigeniae') differ from those that are born alive from unmated mothers ('virginogeniae'). Winged aphids may be blown long distances by the wind and may land by chance in regions which lack their particular food plants. Should we therefore record all the winged aphids found in Suffolk? Probably it is a mistake to regard them as 'Suffolk aphids' unless they have colonized plants. I do not propose to list all the winged or wingless aphids which have been found in Suffolk, on or off plants, but will show the size of the problems involved by analysing the catch of winged aphids from a Single aphid trap in Suffolk in a Single year and relate the trap catch to records of aphids which have appeared in the Suffolk Naturalists' Transactions. I will also point out some of the changes in nomenclature since the time of Claude Morley, who founded our Society. The trap I have chosen is a suction trap operating at 12-2m (40ft.) Over grass at Broom's Barn Experimental Station, Higham, Bury St Edmunds, (Taylor, 1977), which is operated as part of Rothamsted's 'Insect Survey', and the year 1984, the most recent for which all the aphid data are available to me. The trap has operated continuously (except for short periods when the electric power supply failed) since 1965. Any serious Student could obtain details of all the aphids caught from the Entomology Department at Rothamsted Experimental Station, Harpenden, Herts. The Broom's Barn trap was originally operated by me, and now by Mr W. A. Thornhill and Dr A. M. Dewar. Specimens are examined by specialists at Harpenden when there are problems over identification. As far as Suffolk naturalists are concerned the story of aphids in Suffolk begins with Claude Morley. In 1905 he published his Hemiptera of Suffolk, but wrote: 'It has been thought expedient to refrain from Publishing what little is known of the Aphididae and Coccidae of Suffolk.' It was not until the second volume of the Transactions (Morley, 1932) that he listed the aphids which had been found in Suffolk. Morley's list included 87 of the 186 species then known in Britain; 51 species were found in his garden at Monks Soham. H e followed Buckton's Monograph of British Aphidae (1875-1884), published by the Ray Society, and not Theobald's The Plant Lice or Aphidae of Great Britain (1926-27) which became the recognised work on the group. For a list of British aphids today entomologists would refer to Kloet and Hincks (1964) which recognises 526 British species of aphids belonging to 62 genera, but a few more have been named since this list was published. This greatly extended list is due partly to the discovery of aphids which clearly differed from those previously described and also to the work of 'splitters' (entomologists who show that groups of individuals previously thought to be of the same species differ in some major and consistent way, i.e. that they should be considered as of separate species). However, since Morley published his list some 'lumpers' (entomologists who show that groups of individuals considered to be of separate species do not differ sufficiently to justify that Separation, e.g. they may be different colour forms of the same species) have also been at work, and some of Morley's species have 'dis-
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appeared'. Some generic names have been changed, and some new genera created. For example, the first aphid on Morley's 1932 list is Siphonophora rosae L., which today we place in the genus Macrosiphum. The fĂźll scientific name is now therefore Macrosiphum rosae (L.) today. Note that the 'L.' for Linnaeus is now in brackets, signifying that the generic name is not that used by Linnaeus when he described the aphid in 1758. However, the aphid called Siphonophora fragariae by Koch in 1855, which also appeared in Morley's list of Suffolk aphids, is now also thought to be M. rosae (L.); i.e. S. roseaL. = S. fragariae Koch = M. rosae (L.). Synonyms (different names given to the same species) present a major problem for the aphidologist and I am not competent to bring Morley's list fully up to date. To give just one more illustration, Kloet and Hincks (1964) give 32 synonyms for the common Leaf-curling plum aphid, Brachycaudus helichrysi (Kaltb.), which is probably Morley's Aphis myosotidis Koch. It does not encourage one to study aphids! To turn to more recent studies on aphids, in 1984 the Broom's Barn insect trap caught a total of 18,008 winged aphids, comprising 128 different species, roughly one quarter of the total number of species now recognised in B ritain. The number of individuals of the different species varied enormously. For example, more than half the species (74 spp.) were represented by less than 10 individuals, and 84% (108 spp.) by less than 100 individuals. There were more than 1000 each of three species, namely: 6466 Grain aphids, Sitobion avenae (Fab.) (= Morley's Siphonophora granaria Kirby); 2546 Bird-cherry aphids, Rhopalosiphum padi (L.) (= Aphis padi Linn, in Morley's list); and 1787 Sycamore apids, Drepanosiphum platanoides (Sehr.) (a name unchanged since Morley's publication). As might be expected, the abundance of aphids reflects the abundance of their food plants, and 59% of the total catch of aphids at Broom's Barn was formed by the common species which attack cereals and other grasses. In addition to the S. avenae and R. padi there were 900 Rose-grain aphids, Metopolophium dirhodum (Walker), 451 Oat-apple aphids, Rhopalosiphum insertum (Walker) and 294 Grass aphids, Metopolophium feslucae (Theob.). Many cereal growers today find it necessary to spray their crops with insecticide to decrease the damage caused by these aphids feeding, and also to limit the spread of barley yellow dwarf virus which they can carry from plant to plant and which can also greatly reduce the crop yield. Most of the aphids caught in the trap in large numbers were pests of agricultural crops, the most important being the Peach-potato aphid, Myzus persicae (Sulz.), of which 538 were caught in 1984. This species not only attacks potatoes but also sugar beet, lettuce, brassicas and other crops, carrying virus diseases to many of them, including potato leaf-roll, potato rugose mosaic, lettuce mosaic and virus yellows of sugar beet. Other virus vectors (carriers) caught included 726 B. helichrysi, which can carry plum pox, 379 Willow-carrot aphids, Cavariella aegopodii (Scop.), which can carry carrot motley dwarf virus, and 162 Hop-damson aphids, Phorodon humuli (Sehr.), which spread virus disease in hops. Other common aphids which are more important because of the feeding
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damage they cause than as virus vectors included 385 Black-bean aphids, Aphisfabae Group (a pest of sugar beet as well as of beans), 127 Pea aphids, Acryrthosipon pisum (Harris), and 192 Meally plum aphids, Hyalopterus pruni (Geoff.). In 1984 only 45 Meally cabbage aphids, Brevicoryne brassicae (L.) were caught, although these can be an important pest in some years. Few if any of the more important agricultural crops in Suffolk escaped from the attack of aphids. In complete contrast there were 24 species of aphids represented by Single individuals in the trap in 1984, most of interest only to aphidologists. (Yes, such an animal docs exist. Readers may be amused to learn that there is a publication called the Aphidologist's Newsletter, which circulates among some 500 specialists in about 50 countries, giving new lines of work being undertaken, lists of publications and so on). Only two of these species are of economic importance, Aphis nasturtii Kltb., which is a major pest in some countries, e.g. it carries groundnut rosette virus in West Africa, and the Chrysanthemum aphid, Macrosiphoniella samborni (Gill.), which I have known as a pest of Chrysanthemum spp. under glass. To return to Claude Morley, his list of Suffolk aphids (Morley, 1932) gives no biological details of the various species, but he was clearly interested in their biology and not just a collector of names. While he was Honorary Secretary of the Society he published notes on species of economic importance and of only academic interest. For example, he reported that A. pisum spoilt a crop of peas at Waldringfield in June, 1943, so that the crop had to be turned into silage (Morley, 1942), that the Vetch aphid, Megoura viciae BĂźckt, occurred on Dyer's Greenweed, Genista tinctoria L., and an occasion when Pemphigus filaginis (Boyer de Fonsc.) turned Marsh Cudweed, Gnaphalium uliginosum L. among com white with its floculence (scales of wax which protect some aphids from predators) (Morley, 1941). Some of the most interesting aphids to the naturalist are those which cause galls, and Morley (1938) found one of these, Schizoneura (Eriosoma) ulmi (L.), which causes galls in the form of green 'pouches' on elm leaves. He commented: 'Considering the ubiquity of the tree, these perverters are comparatively rare, though known from many Suffolk villages.' In 1984 the Broom's Barn trap caught 25 S. ulmi, and also 21 Tetraneura ulmi (L.), which cause 'Fig galls' on elm (Darlington, 1968). This species also appeared in Morley's original list, as did 7 species of Pemphigus, which cause the characteristic 'purse' and 'spiral' galls on petioles of poplar leaves (Heathcote, 1968). However, only three of Morley's species would be recognised today (P. bursarius (L.), P. filaginis (Boyer de Fonsc.) and P. spirothecae Pass.); Morley's P. bumeliae Sehr, is now placed in the genus Prociphilus, and Pemphigus lactuarius Pass. is considered a synonym of P. bursarius. Hyalopterus pruni also appeared in Morley's list (as H. arundinis Fab.), and I have found this aphid causing galls on Fat Hen, Chenopodium album L., at Barrow. The galls are boat-shaped and very obvious. I will not attempt to comment further on the aphids already reported from Suffolk or to give the Broom's Barn trap records in detail. There are a few recent articles on aphids in the Transactions (e.g. Heathcote, 1969,1984) but no up-to-date list has been published. I am unlikely ever to attempt to
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produce one. I identified the aphids caught in many traps during the years I spent studying aphid-transmitted viruses in Suffolk and I kept a reference collection of aphids, but this was made from specimens collected in all parts of England and I failed to m a k e a list of the species caught in traps or found on plants in Suffolk. Perhaps I should have done so? My readers must be the judge o f t h a t . Happily, l a s the present editorof the Transactions do not have to decide whether such a list would be worth Publishing. However, I must encourage others to record as fully as possible the animals and plants of our county. References Blackman, R . L. & Eastop, V. F. (1984). Aphids on the world's crops. An identification guide. John Wiley & Sons, Chichester. Darlington, A. (1968). The pocket encyclopaedia of plant galls in colour. Blandford Press, London. Heathcote, G . D . (1969). Plant galls. Trans. Suffolk Nat. Soc., 14, 115. Heathcote, G. D. (1969). The defense of aphids against predators and parasites. Trans. Suffolk Nat. Soc., 15, 55. Heathcote, G . D. (1984). Did aphids come to Suffolk from the continent? Trans. Suffolk Nat. Soc., 20, 45. Kloet, G. S. & Hincks, W. D . (1964). A check list of British insects. Part 1. Small Orders and Hemiptera. Royal Entomological Society of London. Morley, C. (1905). Hemiptera of Suffolk. Plymouth: James H . Keys, Printer, Whimple St. Morley, C. (1932). The Hemiptera of Suffolk. First Supplement. Trans. Suffolk Nat. Soc., 2,134. Morley, C. (1938). The elm aphid. Trans. Suffolk Nat. Soc., 4, 68. Morley, C. (1941). The Dyers-weed, Genista tinctoria and its insect fauna. Trans. Suffolk Nat. Soc., 4, 242. Morley, C. (1942). Peas plague. Trans. Suffolk Nat. Soc., 5,104. Taylor, L. R . (1977). Aphid forecasting and the Rothamsted Insect Survey. J. Roy. agric. Soc., 138, 75. Theobald, F. V. (1926-27). The Plant Lice or Aphididae ofGreat Britain. (3 vols.) Headley Bros., Invicta Press, Ashford. D r G . D. Heathcote 2, St Mary's Square, Bury St Edmunds IP33 2AJ
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