Lhf

510 such as the particular odor or taste of a chemical. The chemicals that promote feeding

(phagostimulants) may have no nutritional value for an insect.

Typically saliva lubricates and initiates digestion of the food. However, it may include compounds that act indirectly to facilitate food uptake and digestion or that have functions unrelated to feeding. The gut includes three primary subdivisions, foregut, midgut, and hindgut, and these are typically differentiated into regions of differing function. The foregut is concerned with storage and trituration of food, the midgut with digestion and absorption of small organic molecules, and the hindgut with absorption of water and ions, though some absorption of small organic molecules may occur across the hindgut wall, especially in insects with symbiotic microorganisms in their hindgut.

The digestive enzymes produced match qualitatively and quantitatively the normal composition of the diet. The enzymes may have low specificity, enabling an insect to digest a variety of molecules of a given type, or may be highly specific, for example, when a species feeds solely on a particular food. Gut fluid is buffered within a narrow pH range to facilitate digestion and absorption. Enzymes are released as soon as they are synthesized. Synthesis is regulated so that an appropriate amount of enzyme is produced for the food consumed. Microorganisms in the gut may be important in digestion, especially in wood-eating species, where they degrade cellulose.

Absorption of digestion products occurs mostly in the anterior midgut and mesenteric ceca. It is generally a passive process, though carrier molecules may be used to facilitate the process. The rate at which sugars are absorbed is linked to the rate at which they are converted to trehalose and, hence, glycogen. Lipid absorption is generally slow, with the lipids being converted into di- and triglycerides as they move through the midgut epithelium. Amino acid absorption may be preceded by absorption of water across the midgut wall to produce a favorable gradient for diffusion. However, facilitated diffusion and active transport systems are used for some amino acids in some species.

The fat body is the primary site of intermediary metabolism as well as a site for storage of metabolic reserves. In most insects, trehalose in the hemolymph is the sugar of importance as an energy reserve. Its concentration in the hemolymph is constant and is in dynamic equilibrium with glycogen stored in the fat body. Lipids in the fat body form the major energy reserve molecules and are used in long-term energy-requiring processes such as flight, metamorphosis, starvation, and embryogenesis. The fat body is important in protein metabolism, including amino acid transamination and synthesis of some specific proteins.

The development of resistance to insecticides is normally the result of increased ability of an insect to degrade the insecticides to less harmful and excretable products, but may be related also to increased physical resistance, that is, to structural changes that prevent insecticides from reaching or recognizing the site of action. Metabolic resistance normally develops through the production of more specific or greater quantities of insecticide-degrading enzymes.

Beekeeping for Beginners

Beekeeping for Beginners

The information in this book is useful to anyone wanting to start beekeeping as a hobby or a business. It was written for beginners. Those who have never looked into beekeeping, may not understand the meaning of the terminology used by people in the industry. We have tried to overcome the problem by giving explanations. We want you to be able to use this book as a guide in to beekeeping.

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