insanity In criminal law, a disease, defect, or condition of the mind that renders one unable to understand the nature of a criminal act or the fact that it is wrong. Tests of insanity are not intended as medical diagnoses but rather only as determinations of whether a person may be held criminally responsible for his or her actions. The most enduring definition of insanity in Anglo-American law was that proposed by Alexander Cockburn (1843). Many U.S. states and several courts have adopted a standard under which the accused must lack “substantial capacity either to appreciate the crimi¬ nality of his conduct or to conform his conduct to the requirements of the law.” Some states have abolished the insanity plea, and others allow a find¬ ing of “guilty but mentally ill.” See also diminished responsibility.
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944 I insect ► Institutional Revolutionary Party
insect Any member of the class Insecta, the largest arthropod class, including nearly 1 million known species (about three-fourths of all ani¬ mals) and an estimated 5-10 million undescribed species. Insect bodies have three segments: head, thorax (which bears three pairs of legs and usu¬ ally two pairs of wings), and many-segmented abdomen. Many species undergo complete metamorphosis. There are two subclasses: Apterygota (primitive, wingless forms, including silverfish and bristletails) and Ptery- gota (more advanced, winged or secondarily wingless forms). The approxi¬ mately 27 orders of Pterygota are generally classified by wing form: e.g., Coleoptera (beetles), Diptera (dipterans), Heteroptera (bugs). Insects are found in almost all terrestrial and freshwater and some marine habitats.
Body plan of a generalized insect. The body is usually divided into a head, thorax, and abdomen. The head bears appendages modified into mouthparts and anten¬ nae bearing sense organs. Mouthparts include the toothed mandibles and bladelike maxillae found behind the "upper lip," or labrum. A second pair of maxillae, partly fused, form the "lower lip," or labium. An adult usually has both simple eyes (ocelli) and more-complex faceted compound eyes, as well as a pair of wings on the tho¬ rax. The tarsal segment of the jointed leg often has claws with adhesive pads, enabling the insect to hold onto smooth surfaces. In some insects (including crickets and cockroaches), a pair of feelers (cerci) bearing sense organs are located at the rear of the abdomen. Tiny openings (spiracles) on the thorax and abdomen allow passage of oxygen to and release of carbon dioxide from internal air-filled tubules or tracheae. Sperm from the male is stored in the female's spermatheca until an egg released from the ovary passes through the oviduct. The female may have an ovipositor for depositing eggs.
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insecticide Any of a large group of substances used to kill insects. Such substances are mainly used to control pests that infest cultivated plants and crops or to eliminate disease-carrying insects in specific areas. Inor¬ ganic insecticides include arsenic, lead, and copper compounds. Some organic insecticides are natural, such as rotenone, pyrethrins, and nicotine (see toxin). Others are synthetic, such as chlorinated hydrocarbons (e.g., DDT, dieldrin, lindane); carbamates, related to urea (e.g., carbaryl, carbo- furan); and parathions, organic phosphorus esters. Insect hormones may be included as a class. Insecticides may affect the nervous system, inhibit essential enzymes, or prevent larvae from maturing (e.g., juvenile hor¬ mone). Some are stomach poisons, some inhalation poisons, and others contact poisons. Agents such as inert oils act mechanically, simply block¬ ing the breathing pores. Insecticides vary widely not only in effectiveness against target insects (which may develop resistance) but also in toxicity to nontarget species (including humans) and environmental effects; many of the worst (e.g., DDT) have been banned or their use curtailed.
insectivore Un-'sek-to-.voA Any member of the mammalian order (Insectivora) that includes the hedgehogs, moles, and sometimes shrews (some of which are considered primates by some authorities), or, more generally, any animal that eats mainly insects. The mammalian insecti- vores are generally small, active, and nocturnal. They are found in most parts of the world except Antarctica, Australia, and South America. Most species are solitary (except during the breeding season) and short-lived.
insei Japanese "cloistered government" Rule by retired emper¬ ors who have taken Buddhist vows and retired to cloisters. During the late 11th and the 12th century, governmental control of Japan passed from the Fujiwara family, which had maintained power through marriages to the imperial family, to cloistered emperors. By abdicating, these emperors escaped the control of Fujiwara regents and chancellors; once inside a temple or monastary, they surrounded themselves with capable non- Fujiwara aristocrats. It was the edicts of the cloistered emperor, not the
reigning one, that were obeyed, insofar as any orders were obeyed in a period of increasing collapse of central authority. The practice came to an end with the reign of the emperor Go-Daigo (1318-39). See also shoen.
inside contracting System of manufacturing intermediate between the putting-out system and full factory production. A factory proprietor sup¬ plies to an artisan who then hires the workers needed to make a particu¬ lar part under a contract with the proprietor. Inside contracting was used extensively in the U.S. in the 19th century.
Inside Passage or Inland Passage Natural sheltered sea route along the U.S.-Canadian coast from Seattle, Wash., to Skagway, Alaska. Extending northwest for more than 1,000 mi (1,600 km), it comprises channels and straits between the mainland and islands (including Van¬ couver Island) that protect it from Pacific storms. It is the favoured route for coastal shipping to Alaska. Ports in British Columbia include Victo¬ ria, Vancouver, and Prince Rupert; those in Alaska include Ketchikan, Wrangell, and Juneau.
insider trading Illegal use of insider information for profit in finan¬ cial trading. Since 1934, the Securities and Exchange Commission has pro¬ hibited trading while in possession of material nonpublic information. See also ARBITRAGE, MlCHAEL R. MlLKEN.
insolvency Condition in which liabilities exceed assets so that credi¬ tors cannot be paid. It is a financial condition that often precedes bank¬ ruptcy. In the context of equity, insolvency is the inability to pay debts as they become due; insolvency under the balance-sheet approach means that total liabilities exceed total assets.
insomnia Inability to sleep adequately. The causes may include poor sleeping conditions, circulatory or brain disorders, breathing disorders (e.g., sleep apnea), mental distress (e.g., tension or depression), or physi¬ cal discomfort. Mild insomnia may be treated by improving sleeping con¬ ditions or through traditional remedies such as warm baths, milk, or systematic relaxation. Apnea and its associated insomnia may be treated surgically or mechanically with breathing apparatus. Severe or chronic insomnia may necessitate the temporary use of barbiturates or tranquil¬ izers, but such drugs are often addictive and may be decreasingly effec¬ tive as the body builds up tolerance. Other methods of treatment include PSYCHOTHERAPY and HYPNOSIS.
instinct Involuntary response by an animal, resulting in a predictable and relatively fixed behaviour pattern. Instinctive behaviour is an inher¬ ited mechanism that serves to promote the survival of an animal or spe¬ cies. It is most apparent in fighting and sexual activity. The simplest form is the reflex. All animals have instinct, but, in general, the higher the ani¬ mal form, the more flexible the behaviour. Among mammals, learned behaviour often prevails over instinctive behaviour.
Institut Canadien \a n -ste-'tiE-ka-nad- , ya n \ Literary and scientific soci¬ ety that came into conflict with the Catholic Church in 19th-century French Canada. It was founded in Montreal in 1844 as a discussion forum and free library, and it established branches throughout French-speaking Canada. It criticized the institutionalism of the church in Quebec and dis¬ played books considered undesirable. Church leaders, including Ignace Bourget, bishop of Montreal (1840-76), attacked the institute, which appealed to Rome for support. In 1869 the church condemned the move¬ ment, and most members withdrew.