Population dynamics of the pine needle gall midge, Thecodiplosis japoniensis Uchida et Inouye (Diptera, Cecidomyiidae)
1987
Sone, K. (Kyoto Univ. (Japan). Dept. of Forestry)
The population dynamics of the pine needle gall midge, Thecodiplosis japonensis, was studied during the period from 1975 to 1982 in a young stand of Pinus thunbergii Parl. at Kamigamo Experimental Forest Station of Kyoto University, Kyoto. Life tables were obtained for 6 generations. Population density decreased drastically before the formation of galls and during the period when 3rd-stage larve and pupae were in the soil. Decline in population density was attributed to abiotic factors rather than biotic ones (such as predation, competition, and parasitism). The natural population of T. japonensis was maintained at very low density and was well regulated. Life table analysis for 6 generati1157ons of population data indicated that the key factor was the failure to realize maximum fecundity. The natural populaton seemed to be regulated mainly by mortality prior to gall formation, but the major density-dependent mechanisms which contributed to the population regulation could not be detected from census
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