STUDIES IN THE ECOLOGY OF CARABIDAE (COLEOPTERA). by P.J.M. Greenslade, B.A., D.I.C. A Thesis submitted in part fulfilment of the requirements for the Degree of Doctor of Philosophy in the University of London. Imperial College Field Station, Silwood Park, Sunninghill, Jul y, 1961. Ascot, Berkshire. ABSTRACT. Aspects of the ecology of Carabidae (Coleoptera) were studied on the Imperial College Field Station from autumn 1958 to autumn 1960. Sampling was carried out by pitfall traps and it was found that this method did not give a reliable indication of the relative numbers of species. Allowance was made for this during the course of the work. The life histories of 25 species, common on the Field Station, were investigated with especial reference to annual cycles of adult activity. The vegetation of the drier parts of the Field Station was described and the distribution of the Carabid species related to it. Their daily cycles of activity were investigated and are discussed in relation to habitat and life-history. Work was carried out on distribution of populations of Nebria brevicollis F. and Pterostichus madidus F. Population densities and dispersal were studied by marking and recapture, and some observations were made on populations of four other species. Boundary and area patterns were described, and distribution and dispersal are discussed in relation to the probable effect of weather as a mortality factor. TABLE OF CONTENTS. Page A. INTRODUCTION AND SAMPLING METHODS. I. INTRODUCTION. 1 II. CARABIDAE STUDIED. 1) Review of literature and general biology. 6 2) Species recorded at .Silwood. 11 III. ASSESSMENT OF SAMPLING METHODS. 1) Introduction. 17 2) Pitfall trapping. a) Movement and pitfall catches. 21 b) Behaviour and pitfall catches. 37 c) Weather and activity. 39 d) Trap density and catch. 44 e) Baited traps. 47 3) Discussion. 49 B. ASPECTS OF THE BIONOMICS OF SPECIES. I. LIFE HISTORIES AND ANNUAL CYCLES OF ADULT ACTIVITY. 1) Introduction. 54 2) Description of life histories. a) Nebria brevicollis. 57 b) Pterostichus madidus. 58 c) Other species, 64 d) Classification of life history types. 72 3) Discussion, 78 HABITATS OF CARABIDAE AT SILWOOD. 1) Vegetation of Field Station. 82 2) Distribution of Carabid species. a) Introduction. 88 b) Occurrence of adults in pitfall traps. 89 c) " larvae. 102 d) Temperatures in vegetation types. 103 3) Habitat and food of Carabidae. 105 3) Discussion. 107 Page III. DAILY CYCLES OF ACTIVITY. 1) Introduction. 110 2) Methods. 112 3) Results. a) Times of activity of species. 115 b) Factors affecting times of activity. 116 4) Discussion. 121. IV. THE RELATION BETWEEN ACTIVITY AND HABITAT IN CARABIDAE. 126 C. STUDIES ON SELECTED POPULATIONS. I. METHODS. 1) Marking Carabidae. 141 a) Recapture rates and the analysis of release/ recapture data. 144 II. Nebria brevicollis. 1) Site of population studied. 150 2) Results. a) Distribution. 154 b) Movement of Nebria within the beech litter plot. 158 c) Dispersal beyond the beech litter area. 168 d) Autumn population densities. 179 e) Observations on larvae and callows. 187 f) Aggregation. 195 3) Conclusions. 203 III. Pterostichus madidus. 1) Areas studied and introduction. 204 2) Results. a) Distribution 206 b) Population density 210 c) Dispersal 217 3) Conclusions. 222 IV. OTHER SPECIES. 1) Calathus ydceus. 224 2) Abax parallelopipedus. 227 3) Amara species. 229, 4) Conclusions. 232 1122 D. DISCUSSION. 233 ACKNOWLEDGMENTS. 243 REFERENCES. 244 253 EGURB.E.s• APPENDIX. • 1) Map of Field Station.' 324 2) fieccrded Carabid aggregations. 325 3) A concentrahon of Carabidae at Fleet in Dorset. 326 4) Changes in catch between 1959 and 1960. 328 5) Plates, 340 65 Tables, 343 ....A. INTRODUCTION AND SAMPLING METHODS. I. INTRODUCTION. The object of the work described in this thesis was to investigate the distribution of individuals in populations of selected species of Carabidae. It may be placed in context by a brief discussion of the nature of a population. A population has been defined by Friederichs, quoted by Carpenter (1956), as the sum total of individuals of a species in a given area, while Richards (1960) has suggested as a possible definition that a population is a number of individuals of one species whose lives are sufficiently integrated to have an influence on one another; such a population will normally occupy a spatially fairly well defined area even though the distribution is hardly ever strictly continuous. The term population therefore carries two meanings, one identifying the total number of individuals in a taxonomic group in an arbitrary area, the other referring to a taxonomically related, but more or less spatially isolated group of individuals, communicating more among themselves than with other such groups of the same taxon. However, the proper use of the term is the first (Shorter Oxford English Dictionary, 1952: 'Population the degree in which a place is populated or inhabited; hence, the total number of its inhabitants'), and Gilmour and Gregor (1939) have suggested a terminology to occupy the second meaning. In this a 'deme' is defined as any assemblage of taxonomically closely related individuals, while population in this sense becomes synonymous with 'gamodeme': a deme forming a more or less isolated, local interbreeding community. 2. The concept of the deme has gained wide acceptance in experimental plant taxonomy, and has been used among zoologists by Carter (1951) and others in discussing evolution at the sub-specific level; however, the term deme has frequently been used for what is strictly an isolated interbreeding population or gamodeno. Here population is used loosely to include both its meanings, as to take any other course would be to anticipate final conclusions. Although the population is the unit on which much recent ecological discussion has been based, there have been few studies on the spatial structure of populations of terrestrial invertebrates, that is on the pattern of distribution of individuals and on the amount of movement they show. Such work as has been carried out includes that of Salt and Hollick (1946) and Guild (1952), on the distribution of soil inveltebrates, and of Brian (1947, 1952) on patterns of density and movement in adult Elateridae, and on the distribution of nests of certain ant species. ;lacLeod and Donnelly (1958) and Dowdeswell, Fisher and Ford (1949) have studied movement and dispersal in flying insects. This -rid other work has established that populations commonly show a non-random distribution which may or may not be attributable to properties of the habitat, and that thcre is considerable variation in the extent to which spatial changes in vegetation and other natural barriers irnede dispersal. However, there remain few cases where any attempt has been made to describe the limits of populations of terrestrial invertebrates, or to establish the presence of gamodemes in a continuous habitat (as opposed to a discontinuous to be found for example 3. in ponds or on small islands). Andrewartha and Birch (1954) have argued that distribution and abundance are two aspects of the same phenomenon, and it is difficult to dissociate the problem of the distribution of a population, from that of variation within it in the density of its constituent individuals. Elton (1949) has distinguished populations with area patterns, that is those forcling the typical gamodeme, and those with boundary patterns. However he also describes populations with a periodic distribution centred for example on individuals of a plant dominant, and those with an inverse periodic distribution, where an animal may perhaps only occur where the dominant plant does not. A population showing a typical boundary or area pattern may be composed of high density nodes or centres, of either periodic or inverse periodic distribution. It is one purpose of this work to discover the extent to which Carabid populations agree with these, or any other, hypothetical patterns. A further reason for investigating distribution within populations lies in the context of the factors controlling numbers. Good (1953) has suggested that on the geographical scale plant distribution is limited by climatic factors, while competition and properties of the soil determine abundance within the range of a species. Jeffree (1960) has had some success in relating the distribution of certain insect species to climatic areas, and althouah Lindroth (1953) has questioned the significance of average properties of the macroclimate, determined over a long period, to insects whiGh are directly affected cnly by microclimatic factors, the former are evidently important in setting the broad limits of distributions. 4. Richards (1960) has applied Good's suggestion to insect populations, arguing that at the limit of a species range where its distribution is patchy chance effects of climcte are important in permitting immigration and causing extinction from place to place. In the centre of the range where the microclimate is optimal a more or less steady state will be maintained by Nicholsonian density-dependent controls, while weather causes only relatively minor fluctuations about this value. After an investigation on larvae of the Tent Moth Malacosoma pluviale (Dyar), Wellington (1957) has put forward the suggestion that in studying the factors controlling populations seasonal and areal differences in the behaviour, survival ability and physiological responses of individuals must be considered. Similarly Elton (1949) observed that theories about population change and interaction are based on concepts of mean density, and pointed out that populeaons are in fact split up into groups and centres. The importance of work on the pattern of distribution in populations becomes apparent with their pleas for greater finesse in studies on these controlling factors, and also if Tdchards' suggestions on controlling factors are considered in relation to Lindroth's(1953) observations, on the importance of the microclimate. Here the latter stressed that in any large area where the microclimate permits the existence of a species the micro- climate will only be suitable in certain parts.