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Choristoneura fumiferana
''Choristoneura fumiferana'', the eastern spruce budworm, is a species of moth of the Tortricidae family. It is one of the most destructive native insects in the northern spruce and fir forests of the Eastern United States and Canada. According to one common theory, popularized in the 1970s, periodic outbreaks of the spruce budworm are a part of the natural cycle of events associated with the maturing of balsam fir. The catastrophe theory of budworm outbreaks holds that particularly major infestations occur every 40–60 years, as the result of a cusp-catastrophe event, whereby populations jump suddenly from endemic to epidemic levels. An alternative theory holds that outbreaks are the result of spatially synchronized population oscillations that are caused by delayed density-dependent feedback (from various mortality agents) which are synchronized via a process of entrainment.
The first recorded outbreak of the spruce budworm in the United States occurred in Maine about 1807. Another outbreak followed in 1878. Since 1909 there have been waves of budworm outbreaks throughout the Eastern United States and Canada. The States most often affected are Maine, New Hampshire, New York, Michigan, Minnesota, and Wisconsin. These outbreaks have resulted in the loss of millions of cords of spruce and fir. In 20th century eastern Canada, the major outbreaks occurred in the time periods ~1910-20, ~1940-50, and ~1970-80. Longer-term tree-ring studies suggest that spruce budworm outbreaks have been recurring every three decades or so since the 16th century. Paleoecological studies suggest the spruce budworm has been outbreaking in eastern North America for thousands of years.
==Taxonomy==
When the spruce budworm, ''fumiferana'' (Clemens), was recognized as a Nearctic representative of the genus ''Choristoneura'' Lederer (Freeman 1947),〔Freeman, T.N. 1947. A new generic assignment for'' Archips fumiferana'' (Clemens), the spruce budworm. Can. Entomol. 79:21.〕 the name applied to populations in a variety of geographic regions and biotopes. Later, ''C. pinus'' Free., a distinct form that feeds on pines was established as a separate species, but a large group in the western part of North America remained taxonomically undefined as the “western complex” (Freeman 1953),〔Freeman, T.N. 1953. The spruce budworm ''Choristoneura fumiferana'' (Clem.) and an allied new species on pine (Lepidoptera: Tortricidae). Can. Entomol. 85:121–127.〕 until Freeman (1967)〔Freeman, T.N. 1967. On coniferophagous species of ''Choristoneura'' (Lepidoptera: Tortricidae) in North America. I. Some new forms of ''Choristoneura'' allied to ''C. fumiferana''. Can. Entomol. 99:449–455.〕 established several new species. Field collections of late instar larvae of ''Choristoneura'' populations from a wide range of localities in a wide arc, from the Atlantic seaboard along the edge of the Laurentian Shield to the Mackenzie River area near the Arctic Ocean, yielded ''Choristoneura fumiferana'' (Clem.) ''sensu strico'' only from points east of the Rocky Mountain foothills (Stehr 1967).〔Stehr, G.W. 1967. On coniferophagous species of ''Choristoneura'' (Lepidoptera: Tortricidae) in North America. II. Geographic distribution in accordance with forest regions. Can. Entomol. 99:456–463.〕 The 2-year-cycle budworm, ''C. biennis'' Free. occurs only in the Subalpine forest region (Halliday 1937, Rowe 1959),〔Halliday, W.E.D. 1937. A forest classification for Canada. Can. Dep. Mines and Resources, Dominion For. Serv., Ottawa ON, Bull. 89. 50 p.〕〔Rowe, J.S. 1959. Forest regions of Canada. Ottawa, Dept. Northern Affairs & National Resources, Forestry Branch. 71 p.〕 with alpine fir and interior spruce as hosts. Budworm populations from Rocky Mountain regions south of the area of introgressive hybridization of spruce differ from ''C. biennis'' (Stehr 1967).〔 Other budworms are of little or no consequence with respect to spruces.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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