North American Arthropod Envenomation and Parasitism
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biology
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published 19/11/2007
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SummaryThe phylum Arthropoda contains about four fifths of the known animals of the world, and insects are the largest group of arthropods. Insects are an important part of the biota of all terrestrial and freshwater environments that support life; only in marine environments are they relatively unimportant. More species of insects exist than of any other form of multicellular life, and they may well exceed all other land animals in biomass. Insects can use most animal and plant substances as food, and their feeding plays a vital role in recycling organic compounds. They compete with other organisms for the world's food supplies but are themselves a major food source for many forms of life. They are essential for the pollination of many plants. Insect life cycles are diverse and often complex, involving developmental and sexual stages that are widely different in morphology and ways of life. Although sexual reproduction is the rule, parthenogenesis (unisexual reproduction) and pedogenesis occur. Some groups, such as ants, bees, and termites, have developed a high degree of social organization. During at least part of its life cycle, an insect's body is divided into three distinct regions (head, thorax, and abdomen), with three pairs of legs attached to the thorax. Except for a few primitive or parasitic groups, most adult insects have wings.
Table of Contents
- The greatest direct medical importance of insects is associated with their feeding on human blood and tissue fluids.
- In the eastern United States, blister beetle dermatitis is usually caused by Epicauta species, which occur on many garden plants.
- Patients with delusions of parasitosis are convinced, against all evidence to the contrary, that parasites infest their skin and often their homes and clothing.
- Many patients with parasitophobia know that their fear is groundless but are still unable to overcome it.
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