Contents

1 Introduction 1

1.1 Physiological variation 2

1.2 How much variation? 3

1.3 Diversity at large scales: macrophysiology 7

1.4 Growing integration 9

1.5 This book 10

2 Nutritional physiology and ecology 14

2.1 Method and measurement 16

2.1.1 Artificial diets 16

2.1.2 Indices of food conversion efficiency 16

2.1.3 Use of a geometric framework 17

2.2 Physiological aspects of feeding behaviour 18

2.2.1 Optimal feeding in caterpillars 18

2.2.2 Regulation of meal size: volumetric or nutritional feedback 20

2.2.3 Regulation of protein and carbohydrate intake 22

2.3 Digestion and absorption of nutrients 23

2.3.1 Digestive enzymes and the organization of digestion 23

2.3.2 Gut physicochemistry of caterpillars 26

2.3.3 Absorption of nutrients 27

2.4 Overcoming problems with plant feeding 30

2.4.1 Cellulose digestion: endogenous or microbial? 30

2.4.2 Nitrogen as a limiting nutrient 32

2.4.3 Secondary plant compounds 34

2.5 Growth, development, and life history 39

2.5.1 Development time versus body size 39

2.5.2 Developmental trade-offs between body parts 41

2.6 Temperature and growth 44

2.6.1 Thermal effects on feeding and growth 44

2.6.2 Interactions with food quality 46

3 Metabolism and gas exchange 49

3.1 Method and measurement 50

3.2 Metabolism 51

3.2.1 Aerobic pathways 51

3.2.2 Anaerobic pathways and environmental hypoxia 52

3.3 Gas exchange structures and principles 54

3.3.1 Gas exchange and transport in insects 55

3.3.2 Gas exchange principles 57

3.4 Gas exchange and metabolic rate at rest 60

3.4.1 Gas exchange patterns 60

3.4.2 Discontinuous gas exchange cycles 63

3.4.3 Variation in discontinuous gas exchange cycles 66

3.4.4 Origin and adaptive value of the DGC 68

3.4.5 Metabolic rate variation: size 73

3.4.6 Metabolic rate variation: temperature and water availability 75

3.5 Gas exchange and metabolic rate during activity 79

3.5.1 Flight 80

3.5.2 Crawling, running, carrying 83

3.5.3 Feeding 85

3.6 Metabolic rate and ecology 86

4 Water balance physiology 87

4.1 Water loss 87

4.1.1 Cuticle 88

4.1.2 Respiration 91

4.1.3 Excretion 94

4.2 Water gain 99

4.2.1 Food 100

4.2.2 Drinking 101

4.2.3 Metabolism 102

4.2.4 Water vapour absorption 102

4.3 Osmoregulation 103

4.3.1 Haemolymph composition 103

4.3.2 Responses to osmotic stress 105

4.3.3 Salt intake 107

4.4 Desiccation resistance 107

4.4.1 Microclimates 108

4.4.2 Group effects 109

4.4.3 Dormancy, size, and phylogeny 109

4.5 The evidence for adaptation: Drosophila as a model 111

5 Lethal temperature limits 115

5.1 Method and measurement 115

5.1.1 Rates of change 117

5.1.2 Measures of thermal stress 118

5.1.3 Exposure and recovery time 120

5.2 Heat shock, cold shock, and rapid hardening 121

5.2.1 Acclimation 122

5.2.2 Heat shock 124

5.2.3 Cold shock 131

5.2.4 Relationships between heat and cold shock responses 134

5.3 Programmed responses to cold 137

5.3.1 Cold hardiness classifications 137

5.3.2 Freeze intolerance 139

5.3.3 Cryoprotective dehydration 144

5.3.4 Freezing tolerance 145

5.4 Large-scale patterns 146

5.4.1 Cold tolerance strategies: phylogeny, geography, benefits 147

5.4.2 The geography of upper and lower limits 150

6 Thermoregulation 154

6.1 Method and measurement 155

6.2 Power output and temperature 157

6.3 Behavioural regulation 160

6.3.1 Microhabitats and activity 161

6.3.2 Colour and body size 163

6.3.3 Evaporative cooling in ectothermic cicadas 165

6.4 Butterflies: interactions between levels 166

6.4.1 Variation at the phosphoglucose isomerase locus 167

6.4.2 Wing colour 167

6.4.3 The influence of predation 168

6.5 Regulation by endothermy 169

6.5.1 Preflight warm-up 170

6.5.2 Regulation of heat gain 170

6.5.3 Regulation of heat loss 171

6.6 Endothermy: ecological and evolutionary aspects 172

6.6.1 Bees: body size and foraging 173

6.6.2 Bees: food quality and body temperature 175

7 Conclusion 177

7.1 Spatial variation and its implications 177

7.1.1 Decoupling of upper and lower lethal limits 177

7.1.2 Latitudinal variation in species richness and generation time 180

7.1.3 Spatial extent of the data 181

7.2 Body size 182

7.3 Interactions: internal and external 185

7.3.1 Internal interactions 185

7.3.2 External interactions 186

7.3.3 Interactions: critical questions 187

7.4 Climate change 188

7.5 To conclude 190

References 191

Index

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