Ost

720 Insects that are preyed on by other organisms may reduce their chances of being eaten by burrowing into a substrate, hiding in vegetation, becoming active during a restricted period, or through camouflage. Some species are aposematically colored and distasteful. Distasteful species may resemble each other (Mullerian mimicry), so that when a predator learns their pattern of coloration, all species are protected. An edible species (the mimic) may resemble an inedible (distasteful) species (the model) to avoid detection (Batesian mimicry), though this method requires that the population density of the model be much greater than that of the mimic.

Most insect predators, parasitoids, and parasites are relatively or highly prey-(host-)specific. They may find suitable prey in a sequence of steps: (1) location of the prey's habitat, often by the odor of the prey's food (especially if this has been damaged by the prey); (2) search for and location of prey, stimulated by specific odors, for example, that of the prey's feces; and (3) acceptance of prey, which may be dependent on its size, color, shape, texture, or taste.

Diseases caused by pathogenic microorganisms, particularly bacteria, viruses, fungi, protozoa, and nematodes, are important regulators of insect populations. Often the incidence of disease in a population is low and the disease is said to be in the enzootic stage. When conditions are such that a disease can spread rapidly through a population, the disease is described as in the epizootic stage. The occurrence of an epizootic depends on a pathogen's virulence, infectivity, and viability, on the host's density, distribution, and mobility, and on abiotic factors such as temperature, humidity, light, and wind. The normal route of entry of pathogens is via the midgut, though fungi commonly enter via the integument. How microorganisms cause a pathological condition is varied. Bacteria may damage the midgut epithelium, causing starvation, or may invade other tissues causing septicemia and/or liberating toxins. Viruses disrupt the metabolism of the host's cells. Fungi may physically disrupt tissues, or may secrete histolyzing or toxic substances. Protozoa have a generally debilitating effect and may release toxins. Nematodes may be parasitic or pathogenic. Parasitic species typically cause protracted or morphologically abnormal larval development, or reduced fecundity. Some feed on selected organs, for example, the gonads, and thereby exert specific effects on the host. Pathogenic nematodes release their mutualistic bacteria into the host's body cavity, causing rapid septicemia and death of the host.

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.

Get My Free Ebook


Post a comment