SURVIVORSHIP AND OTHER FACTORS RELATING TO POPULATION FLUCTUATIONS OF THE PINE NEEDLE GALL MIDGE, THECODIPLOSIS JAPOiVENSIS (DIPTERA, CECIDOMYIIDAE)

概要

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Comparative studies of the population dynamics of the pine gall midge, Thecodiplosis japonensis, were made in four Korean red pine forests. Survivorship curves developed from these studies indicate that most gall midge mortality occurs in three periods of the larval stage : 1) in newly hatched larvae, prior to gall formation, 2) in young larvae, after the galls have formed, and 3) in mature larvae that have dropped to the soil. Atsites where midge populations were decreasing following a period of severe damage, mortality rates were much higher in all developmental stages than at sites with increasing populations. Examples of density-dependent mortality which can combine to suppress populations or stabilize them are : mortality of newly hatched larvae induced by physiological changes of needles resulting from severe midge damage ; larval mortality resulting from early gall withering ; and mortality caused by Piutygaster mutsutama, a wasp parasite that attacks the midge larvae very early but kills them after they have dropped to the soil.
九州大学の論文