Ecological Methods: With Particular Reference to the Study of Insect Populations

the virtual impossibility of extracting the many different species from a habitat with equal efficiency by a single method (e.g. Nef, 1960). 1.1 Population estimates Population estimates can be classified into a number of different types; the most convenient classification is that adopted by Morris (1955), although he used the terms somewhat differently in a later paper (1960). 1.1.1 Absolute and related estimates The animal numbers may be expressed as a density per unit area of the ground of the habitat. Such estimates are given by nearest neighbour and related techniques (Chapter 2), marking and recapture (Chapter 3), by sampling a known fraction of the habitat (Chapter 4-6) and by removal sampling and random walk techniques (Chapter 7). Absolute population The number of animals per unit area (e.g. hectare, acre). It is almost impossible to construct a budget or to study mortality factors without the conversion of population estimates to absolute figures, for not only do insects often move from the plant to the soil at different developmental stages, but the amount of plant material is itself always changing. The importance of obtaining absolute estimates cannot be overemphasized.

1 Introduction to the study of animal populations.- 1.1 Population Estimates.- 1.1.1 Absolute and related estimates.- Absolute population.- Population intensity.- Basic population.- 1.1.2 Relative estimates.- 1.1.3 Population indices.- 1.2 Errors and Confidence.- 2 The sampling programme and the measurement and description of dispersion.- 2.1 Preliminary Sampling.- 2.1.1 Planning and field work.- 2.1.2 Statistical aspects.- The normal distribution and transformations.- Taylor’s power law.- Choosing the transformation.- Checking the adequacy of the transformation.- The use of probability paper.- Analysis of variance.- 2.2 The Sampling Programme.- 2.2.1 The number of samples per habitat unit.- Subdivision of the habitat.- The number of samples per subdivision.- 2.2.2 The sampling unit, its selection, size and shape.- 2.2.3 The number of samples.- 2.2.4 The pattern of sampling.- 2.2.5 The timing of sampling.- 2.3 Dispersion.- 2.3.1 Mathematical distributions that serve as models.- Binomial family.- Calculating k of the negative binomial.- Testing the fit of the negative binomial.- Calculating a common k.- Logarthmic and other contagious models.- Implications of the distribution models and of changes in the type of distribution.- Comparison of aggregation indices.- 2.3.2 Biological interpretation of dispersion parameters.- Index of dispersion-the departure of the distribution from randomness.- ‘k’ of the negative binomial — an index of aggregation in the population.- ‘b’of Taylor’s power law — an index of aggregation for the species.- Lloyd’s mean crowding and Iwao’s patchiness regression — indices for the population and species.- Iwao’s ?-index — a measure of colony area.- Breder’s equations — a measure of the cohesion of aggregations.- Deevey’s coefficient of crowding.- 2.3.3 Nearest neighbour and related techniques — measures of population size or of the departure from randomness of the distribution.- Nearest neighbour methods.- Closest individual or distance method.- 2.4 Sequential Sampling.- 2.5 Presence or Absence Sampling.- 2.6 Sampling a Fauna.- 2.7 Biological and Other Qualitative Aspects of Sampling.- 3 Absolute population estimates using marking techniques.- 3.1 Methods of Marking Animals.- 3.1.1 Group marking methods.- Paints and solutions of dyes.- Materials.- Application.- Dyes and fluorescent substances in powder form.- Labels.- Mutilation.- Marking internally by injection.- Marking by feeding with dyes.- Genes, mutant and normal.- Rare elements.- Radioactive isotopes.- Labels.- Incorporation in tissues.- Detection.- Autoradiographic discrimination between32P and35S marked insects.- 3.1.2 Individual marking methods.- 3.1.3 Handling techniques.- 3.1.4 Release.- 3.2 Capture-Recapture Methods of Estimating Population Parameters.- 3.2.1 Lincoln Index type methods.- Assumptions.- The validity of the assumptions.- Marking has no effect.- Equal catchability.- Methods of calculation.- The Lincoln Index.- Other single mark methods.- Review of methods for a series of marking occasions.- Choice of method for a series of marking occasions.- The Fisher — Ford method.- Bailey’s triple-catch method.- The Jolly — Seber stochastic method.- Manly & Parr’s method.- 3.2.2 Frequency of capture methods (Schnabel census).- 3.2.3 Craig’s method: constant probability of capture.- 3.2.4 Change in ratio methods (Kelker’s selective removal).- 4 Absolute population estimates by sampling a unit of habitat —air, plants, plant products and vertebrate hosts.- 4.1 Sampling from the AIR.- 4.1.1 Sampling apparatus.- Exposed cone type of suction trap.- Enclosed cone types of suction trap.- Rotary and other traps.- Comparison and efficiencies of the different types of suction traps.- 4.1.2 Conversion of catch to aerial density.- 4.1.3 Conversion of density to total aerial population.- 4.2 Sampling From Plants.- 4.2.1 Assessing the plant.- 4.2.2 Determining the numbers of insects.- Direct counting.- The separation of exposed small animals from the foliage on which they are living.- Knockdown — by chemicals, jarring and heat.- Brushing.- Washing.- Imprinting.- The expulsion of animals from tall vegetation.- Jarring or beating.- Chemical knockdown.- Collection of naturally descending animals.- The extraction of animals from herbage and debris.- Suction apparatus.- Cylinder or covering method.- Tents for sampling strongly phototactic animals.- Extraction by heat, drying and/or flotation.- Methods for animals in plant tissues.- Dissection.- Bleaching and/ or selective staining.- X-rays.- Methods based on the different mass of the whole and the infested material.- Aural detection.- 4.2.3 Special sampling problems with animals in plant material.- The marking of turf samples.- The sampling of bulk grain.- The sampling of bark.- 4.3 Sampling from Vertebrate Hosts.- 4.3.1 Sampling from living hosts.- Searching.- Combing.- Fumigation.- 4.3.2 Sampling from dead hosts.- Searching and combing.- Fumigation.- Dissolving.- Clearing.- Washing.- 4.3.3 Sampling from vertebrate ‘homes’.- 5 Absolute population estimates by sampling a unit of habitat-soil and litter.- 5.1 Sampling.- 5.2 Mechanical Methods of Extraction.- 5.2.1 Dry sieving.- 5.2.2 Soil washing (or wet sieving).- 5.2.3 Soil washing and flotation.- 5.2.4 Flotation.- 5.2.5 The separation of plant and animal matter by differential wetting.- 5.2.6 Centrifugation.- 5.2.7 Sedimentation.- 5.2.8 Elutriation.- 5.2.9 Sectioning.- 5.3 Behavioural or Dynamic Methods.- 5.3.1 Dry extractors.- Large Berlese funnel.- Horizontal extractor.- High gradient (Multiple canister) extractor.- Kempson bowl extractor.- 5.3.2 Wet extractors.- Baermann funnel.- Hot water extractors.- Sand extractors.- Cold water extractor.- Mistifier.- 5.3.3 Chemical extraction.- 5.3.4 Electrical extraction.- 5.4 Summary of the Applicability of the Methods.- 6 Absolute population estimates by sampling a unit of habitat — freshwater habitats.- 6.1 Open Water.- Nets.- Pumps and baling.- The Clarke — Bumpus plankton sampler.- The Belleville mosquito sampler.- 6.2 Vegetation.- Sampling cylinder for floating vegetation.- Wisconsin trap.- The Gerking sampler.- McCauley’s samplers.- Sampling cages.- 6.3 Bottom Fauna.- The ‘Planting’ of removable portions of the substrate.- Lifting stones.- Cylinders and boxes for delimiting an area.- Movable nets — drags.- Dredges and other devices for removing portions of the substrate.- Air-lift and suction devices.- 7 Relative methods of population measurement and the derivation of absolute estimates.- 7.1 Factors Affecting the size of Relative Estimates.- 7.1.1 The ‘phase’ of the animal.- 7.1.2 The activity of the animal.- 7.1.3 Variation in the responsiveness of different sexes and species to trap stimuli.- 7.1.4 The efficiency of the trap or searching method.- 7.2 The uses of Relative Methods.- 7.2.1 Measures of the availability.- 7.2.2 Indices of absolute population.- 7.2.3 Estimates of absolute population.- ‘Calibration’ by comparison with absolute estimates.- Correcting the catch to allow for variations in trap efficiency.- Line transects.- Removal trapping or collecting.- 7.2.4 Collecting.- 7.3 Relative Methods — Catch Per Unit Effort.- 7.3.1 Visual observation.- 7.3.2 Population estimates from line transects.- 7.3.3 Observation by Radar.- 7.3.4 Aural detection.- 7.3.5 Exposure by plough.- 7.3.6 Collecting with a net or similar device.- 7.4 Relative Methods — Trapping.- 7.4.1 Interception traps.- Air — flight traps.- Water — aquatic traps.- Land — pitfall and other traps.- 7.4.2 Flight traps combining interception and attraction.- Sticky traps.- Water traps.- 7.4.3 Light and other visual traps.- Mode of action and limitations.- The effects of trap design on catch.- Techniques and types of trap.- The Rothamsted trap.- The Robinson trap.- The Pennsylvanian and Texas traps.- The New Jersey trap.- The Haufe — Burgess visual trap.- The Manitoba horse fly trap.- Aquatic light traps.- 7.4.4 Traps that attract the animal by some natural stimulus or a substitute.- Shelter traps.- Trap host plants.- The use of vertebrate hosts or substitutes as bait.- Moving baits.- Stationary baits.- Bait traps.- Traps.- Baits or lures.- Sound traps.- 8 Estimates based on products and effects of insects.- 8.1 Products.- 8.1.1 Exuviae.- 8.1.2 Frass.- Identification.- The rate of frass production.- Efficiency of collection.- 8.1.3 Other products.- 8.2 Effects.- 8.2.1 Effects due to an individual insect.- 8.2.2 General effects — damage.- Criteria.- Economic damage.- Loss of yield.- The amount of plant consumed.- Determining the relationship between damage and insect populations.- 9 Observational and experimental methods for the estimation of natality, mortality and dispersal.- 9.1 Natality.- 9.1.1 Fertility.- 9.1.2 Numbers entering a stage.- 9.1.3 The birth-rate from mark and recapture data.- 9.2 Mortality.- 9.2.1 Total.- 9.2.2 The death-rate from mark and recapture data.- 9.2.3 Climatic factors.- 9.2.4 Biotic factors.- Examination of the prey (host).- Examination of the predator.- Serological methods.- Labelled prey.- Predator or parasite exclusion techniques.- Mechanical or other barriers.- Elimination of predator or parasite.- Direct observation.- Experimental assessment of natural enemies.- Death rate of prey/prey density.- Death rate of prey/predator density.- Predator dispersion/prey dispresion.- Fecundity, developmental and survival rates of predators/prey density.- The role of other prey.- Changes during development of the predator.- Changes due to other animals.- Climatic and similar effects.- 9.5 Dispersal.- 9.3.1 Laboratory assessments.- 9.3.2 The use of marked or introduced animals.- The measurement and description of dispersal.- The detection of heterogeneity, with respect to the rate of dispersal, in the individuals of the population.- The numbers at various distances from the release point.- The fall-off of density with distance.- The mean-distance travelled and the rate of dispersal.- The number of marked animals that have left an area.- The rate of population interchange between two areas.- The description of population displacement in relation to its dispersion.- The measurement and description of home range and territory.- Minimum area method.- The matrix index.- 9.3.3 Direct field measurements.- The elimination of emigration.- The use of quadrat counts of unmarked individuals.- The rate of colonization of a new habitat.- The direction of migration.- 10 The Construction, description and analysis of age-specific life-tables.- 10.1 Types of Life-Table and the Budget.- 10.2 The Construction of a Budget.- 10.2.1 Graphical method.- 10.2.2 Richards & Waloff’s first method.- 10.2.3 Manly’s method.- 10.2.4 Birley’s method.- 10.2.5 Ruesink’s method.- 10.2.6 Dempster’s method.- 10.2.7 Richards & Waloff’s second method.- 10.2.8 Kiritani, Nakasuji & Manly’s method.- 10.3 The Description of Budgets and Life-Tables.- 10.3.1 Survivorship curves.- 10.3.2 The life-table and life expectancy.- 10.3.3 Life and fertility tables and the net reproductive rate.- 10.3.4 Population growth rates.- 10.3.5 The calculation of r.- 10.4 The Analysis of Life-Table Data.- 10.4.1 The comparison of mortality factors within a generation.- Apparent mortality.- Real mortality.- Indispensible mortality.- Mortality — survivor ratio.- 10.4.2 The simple statistical relationship ofpopulation size to a factor.- 10.4.3 Survival and life budget analysis.- Varley & Gradwell’s method.- The investigation of the roles of different factors in single- generation budgets.- 11 Age-grouping of insects, time-specific life-tables and predictive population models.- 11.1 Age-Grouping of Insects.- 11.1.1 Cuticular bands.- 11.1.2 Sclerotization and colour changes in the cuticle and wings.- 11.1.3 Developmental changes in the male genitalia.- 11.1.4 Changes in the internal non-reproductive organs.- 11.1.5 The condition of the ovaries and associated structures.- 11.1.6 Indices of copulation.- 11.1.7 Changes in weight.- 11.1.8 ‘Wear and tear’.- 11.2 Time-Specific Life Table and Survival Rates.- 11.3 Predictive Population Models.- 11.3.1 Physiological time.- 11.3.2 Life-table parameters.- 11.3.3 Recruitment in the field.- 11.3.4 Empirical models.- 11.3.5 Intrinsic rate models and variable life tables.- 11.3.6 Lewis-Leslie matrices.- 12 Systems analysis and modelling in ecology.- 12.1 Types of Systems Model.- 12.1.1 Dioristic models.- 12.1.2 Component models.- 12.1.3 Strategic models.- Deductive and mixed models.- Inductive models.- 12.1.4 Management models.- Population management models.- Ecosystem (biome) models.- 12.1.5 Statistical models.- 12.2 Analysis and Simulation in Models.- 12.3 Deterministic and Stochastic Models.- 12.4 Difference and Differential Models.- 13 Diversity, species packing and habitat description.- 13.1 Diversity.- 13.1.1 Description of ? and ? diversity.- Models for the S:N relationship.- Geometric series.- Logarithmic (or log) series.- Log normal distribution.- Mac Arthur’s broken stick.- Non-parametric indices.- Shannon — Weaver function.- Simpson — Yule index (D).- Berger — Parker Dominance index.- Which model or index?.- Procedure.- 13.1.2 Description of ?-diversity.- Indices.- The sorting of indices.- Trellis diagram.- Dendrogram.- Cluster analysis.- Multivariate methods.- Gradient description.- 13.2 Species Packing.- 13.2.1 Measurement of interspecific association.- The departure of the distribution of presence or absence from independence.- The contingency table.- Coefficients of association.- Proportion of individuals occuring together.- 13.2.2 Measurement of resource utilization.- Species packing in terms of mean and width of resource utilization specturm (‘ d/w’ method).- Species packing in terms of proportional utilization of different resource states (‘pi method’).- 13.2.3 Niche size and competition coefficients.- 13.3 Habitats.- 13.3.1 Qualitative.- 13.3.2 Quantitative.- 14 The estimation of productivity and the construction of energy budgets.- 14.1 Estimation of Standing Crop.- 14.1.1 Measurement of biomass.- 14.1.2 Determination of caloric value.- 14.2 Estimation of Energy Flow.- 14.2.1 The measurement of production.- 14.2.2 The measurement of feeding and assimilation.- The quality of the food eaten.- Feeding and assimilation rates.- Radiotracer techniques.- Gravimetric techniques.- Indicator methods.- 14.2.3 The measurement of the energy loss due to respiration and metabolic processes.- Calorimetric.- The exchange of respiratory gases.- The energy equivalents of oxygen and carbon dioxide.- The respiratory rate.- Gas analysis.- 14.3 The Energy Budget, Efficiencies and Transfer Coefficients.- 14.3.1 The energy budget of a population (or Trophic level).- 14.3.2 Energy transfer across trophic links.- 14.4 Assessment of Energy and Time Cost Strategies.- Author Index.- General Index.