Frontispiece. Birch leaf roller, Deporaus betulae (L. ) (Attelabidae) A phytophagousweevil of birch, alder and hazel, remains of which were recovered from modem woodlands,and death assemblagesof Late Bronze Age date at St George's Field, York. Magnification approximately x 25. INSECT DEATH ASSEMBLAGES AND THE INTERPRETATION OF WOODLAND HISTORY: evidence from the Vale of York Michael JamesHill submitted for the degree of D. Phil. University of York, Environmental Archaeology Unit October 1993 Abstract Insect death assemblages (the accumulated remains of insect body parts), preserved in archaeological and natural deposits, have often been used as an aid to interpreting past environments. This thesis assessesthe extent to which beetle and bug assemblages can be used in palaeoenvironmental reconstruction, particularly for woodland habitats, using data from both modern and fossil assemblages from the Vale of York. The study of insect assemblagesaccumulating in modem woodland habitats suggests that species composition may be used to determine whether an assemblage formed under woodland conditions. However, the taxa present in an assemblage appear to be insufficiently constant to permit further interpretation of woodland structure using statistical methods. The use of `ecological groups' to classify species appears to be of value in reducing the complexity of species lists without reducing the interpretative value of the assemblage. The numbers in the broad ecological groups identified could be used to provide a reliable guide to the general ecological conditions under which an assemblage formed. The tree species present in a woodland were well-represented amongst the host- specific phytophagous insects present in the insect assemblages studied, but certain groups of plants, such as the woodland herbs, were not represented. Fossil insect assemblagesfrom two sites in the Vale have been studied.It appeared that the Late Bronze Age faunas from St George's Field, York, were laid down in (or near) old woodland rich in woodland insect taxa. However, from deposits dated is 180 BC - AD 500 at Thornton, there little evidence for habitats beyond the local marshland in which the assemblages formed, and none for woodlands. The results of these studies suggest that the depositional environment, and post-depositional conditions can both act as important influences on the nature of preserved death assemblages, and this must be considered when they are used to reconstruct past environments. Contents Acknowledgements 1 ........................................... Author's Declaration 2 .......................................... Chapter 1 Introduction 3 ......................................... 1.1 Woodlands, landuse history insect death 3 and assemblages.......... 1.2 The Vale York 4 of ...................................... 1.3 Other evidence available for the reconstruction of past woodland extent 14 and management ..................................... 1.4 The insect death in 18 use of assemblages woodland archaeology ....... 1.5 Aims 20 of this project .................................... 1.6 Nomenclature 20 conventions ................................ Chapter 2 The insects 21 classification of according to their ecology ........... 2.1 Introduction 21 .......................................... 2.2 Some 22 problems associated with the ecological coding technique ..... 2.3 Hostplants 27 ........................................... 2.4 The 28 ecological classification system used ..................... 2.5 A list of the major publications used for the ecological classification of insect 36 species ....................................... Chapter 3 Modern insect death 38 assemblages .......................... 3.1 Introduction 38 .......................................... 3.2 The 38 modern sites studied ................................. 3.3 Field investigations Yorkshire 44 of modern woodlands ............. 3.4 Laboratory 50 methods .................................... 3.5 Results 54 ............................................. 3.6 Discussion 92 ........................................... 3.7 Conclusions 99 .......................................... Chapter 4 The Thornton, Humberside 101 palaeoecology of a site at ............ 4.1 Introduction 101 .......................................... 4.2 The Site 101 ............................................ 4.3 Methods 104 ............................................ 4.4 Results 106 ............................................. 4.5 Rare insect 114 and notable species ............................ 4.6 Discussion 117 ........................................... 4.7 Conclusions 122 .......................................... Chapter 5 The St George's Field, York 123 nalaeoecology of a site at ........... 5.1 Introduction 123 .......................................... 5.2 The Site 123 ............................................ 5.3 Methods 126 ............................................ 5.4 Results 127 ............................................. 5.5 Discussion 143 ........................................... 5.6 Conclusions 152 .......................................... Chapter 6 Modern fossil insect 154 and assemblages: an overview ............. 6.1 Communities Death 154 and assemblages ........................ 6.2 Catchment the depositional 156 areas and environment ............... 6.3 Post-depositional 159 processes ............................... 6.4 Insect-plant 160 relationships ................................. 6.5 Future 161 work .......................................... Definitions 163 and abbreviations .................................... Bibliography 164 ................................................ Appendices Appendix 1: Specieslists of beetles and bugs from modern Yorkshire woodland 184 sites .................................................. Appendix 2: Species lists of beetles and bugs from Thornton and St. George's Field 202 ................................................. Appendix 3: Notes on the occurrenceof beetle speciesin woodland habitats CARABIDAE 220 ........................................... CURCULIONOIDEA 234 ...................................... Figures Frontispiece:' Deporaus betulae, a phytophagousweevil of birch, alder and hazel. 1.1 The England 6 north-east of .......................... 1.2 The Vale York 7 of ................................ 2.1 Schema for insects 30 the ecological classification of .......... 2.2 Subdivision of the woodland habitat among characteristic beetle 35 groups ............................................ 3.1 Structure database 53 of tables making up the relational ........ 3.2 The size of modem assemblages, in terms of number of taxa (S) individuals (N) 55 and number of ....................... 3.3 S plotted against the logarithm of N for all modern 55 assemblages .:................... ............. 3.4 Plot of 2-dimensional MDS solution for 02 dissimilarity data based lists from 58 on species modern woodlands ............ 3.5a-h Mean S and N in each ecological group, for modern death 68 assemblages. ....................:........, ....... 3.6a-g Proportions of the total assemblagein each ecological group, with a measure of the remoteness of potential sources of insects 70 ........................................ 3.7 Mean percentageof assemblagein each ecological group, for 75 woodland and non-woodland sites ..................... 3.8a-h Rank-abundance for 82 plots modern assemblages..... :..... 3.9 Berger-Parker(d) versus Simpson's (D) indices of diversity for modern assemblages .............................. 87 4.1 Map Thornton 102 of the area around site .................. 4.2 Major types the Thornton 103 soil around site ................ 4.3 Stratigraphy Thornton 104 of site ........................ 4.4 Proportion of the total number of species in each ecological for Thornton 109 group, assemblages ...................... 4.5 Proportion of the total number of individuals in each ecological for Thornton 109 group, assemblages ....................... 4.6 Percentageof the total number of individuals in aquatic and 110 marshland groups .................................. 5.1 Map York, St George's Field 124 of showing position of ........ 5.2 Stratigraphy St George's Field 125 of ...................... 5.3 Calibrated dates, St George's Field 127 radiocarbon ............ 5.4 Assemblage (N), depth 130 sizes against ................... 5.5 Proportion of the total N falling into each ecological group, for St George's Field 132 assemblages ........................... 6.1 The formation fossil death 154 of a assemblage............... Tables 3.1 Modern 43 nettlebed samples ............................... 3.2 Vegetation layers Allerthorpe Common 45 at woods .............. 3.3 Field & ground layers, litter and dead wood, Allerthorpe Common Woods 45 ............................................. 3.4 Vegetation layers Dunnington Rabbit Warren 46 at ............... 3.5 Field & ground layers, litter and dead wood, Dunnington Rabbit Warren 46 ............................................ 3.6 Vegetation layers Stub Wood, SW2 47 at site ................... 3.7 Field & layers, SW2 48 ground site .......................... 3.8 Dead & litter, SW2 48 wood site ............................ layers Stub Wood, SW3 48 3.9 Vegetation at site ................... 3.10 Field & layers, SW3 49 ground site .......................... 3.11 & litter, SW3 50 Dead wood site ............................ 3.12 Values for water content and pH of soil and litter layers for modern Yorkshire 50