<p> NUTRITIONAL ECOLOGY OF PLANT FEEDING INSECTS</p><p>(Or: “What do Insects Need, and Where’s (& How) the Best Place to get It?”)</p><p>I. Insect Nutritional Requirements A. Carbohydrates: Polyhedroxyl aldehydes & ketones 1. Classifications a. Mono-, di-, oligo-, poly- saccharides b. Pure, Derived, Conjugated 2. Use: Very similar to mammals a. Energy b. Vitamin synthesis c. Structure: Particularly chitin, Some pigments (protection) d. Storage, cold hardiness, pheromone synthesis d. Defensive compounds 3. Unutilizable & toxic carbohydrates a. Ripe berries often rich in sorbose (unutilizable by insects) b. 5-C sugars often toxic: Galactose Arabinose B. Lipids: Polyunsaturated fatty acids & sterols 1. Use a. Structural compounds: cell membranes, cuticle b. Source of metabolic energy: Linked to flight behavior c. Water conservation 2. Absolute requirements a. Polyunsaturated fatty acids: C18 b. Sterols: 1. Structure 2. Endocrine system: Ecdysone precursor 3. Carrier Molecules: Lipoproteins C. Proteins: 1. Uses: extremely broad range a. Structure, enzymes, DNA & RNA, storage, etc. b. Bioluminescence, Silk 2. Requires dietary Nitrogen 3. Some N containing compounds are toxic: Alkaloids, cyanogenic glycosides, etc. D. Water E. Vitamins & Micronutrients: Coenzymes (K,P, Mg, Zn, Fe, Mn, Ca)</p><p>II. Insect Nutritional Physiology A. Digestion & Excretion 1. Carbohydrates a. Digestion: Simple carbohydrases b. Excretion 2. Lipids: Simple hydrolysis 3. Proteins: Enzymes (sensitive to Ph, etc.) B. Nutritional Indices: Waldbauer 1968 1. Definitions Relative Growth Rate (RGR) = Biomass Gain/Original size per day Biomass Gain = Ingested - Feces - Metabolism Relative Consumption Rate (RCR) = Food Ingested/Original size per day Approximate Digestibility (AD) = (Ingested - Feces)/Ingested Efficiency of Conversion of Digested Food (ECD) = Biomass G/I-F Efficiency of Conversion of Ingested Food (ECI) = Biomass G/I</p><p>RGR = RCR * ECD * AD ECI = AD * ECD</p><p>2. Homeostasis C. The dilemma to eating plants: N availability; Implications III. Variable Distribution of Nutrients: Nitrogen A. Plant Taxa B. Plant Part Storage tissues (seeds) > Organs with high turnover rates (Flowers, fruits, leaves, cambium > Saps: (Phloem > xylem sap) > Wood C. Plant Phenology: Plant Age, Tissue Age D. Environmental Conditions E. Interactions with Allelochemicals </p><p>Water A. Plant Taxa Forbs> Grasses> Shrubs> Trees B. Plant Part 1. Foliage > wood C. Plant Phenology: Younger tissue has higher water content D. Environmental Conditions</p><p>Variations in insect performance on different plant parts & taxa Approximate digestibilities: tree foliage > forb foliage ECI’s; AD’s Seeds, Pollen > Leaves > Wood</p><p>IV. Mechanisms for contending with low Nitrogen Availability A. Higher food consumption or development time B. Specialized digestive systems & symbiotic relationships 1. Elongated side pouches (caecae) house bacteria, yeasts, protozoa 2. External symbionts C. Occasional cannibalism & carnivory D. Switching among plant parts E. Regulation of plant chemistry </p><p>V. Implications of Variable Nutrient Quality A. Plant Defense Theory 1. Induced Defenses 2. Interactions with Allelochemicals 3. Plant Stress Theory 4. Low nutritional quality as a form of defense? Berenbaum B. Natural & Sustainable Resource Management 1. Breeding for high quality plants 2. Fertilization & Irrigation 3. Acid Precipitation:</p>