Miscellaneous : Abstracts of Ph . D . Dissertations Published in 1987 : Studies on the Population Dynamics of the Pine Needle Gall Midge , Thecodiposis japonensis Uchida et Inouye , in the Frontal Zones of its infestation

Comparative studies of the population dynamics of the pine needle gall midge, Thecodiplosis japonensis Uchida et Inouye, were made in four Korean red pine forests located in Chungchongnamdo (province), where the midge appeared recently. the results were summarized as follows 1. After of the pine needle gall midge into a red pine forest, its annual changes in patterns of population density reached peak severity gradationally arid then decreased rapidly to non-injurious level thereafter. And the positive correlation-ship between percentages of current needles infested and the number of adults emerged in unit area was not found within a generation. 2. The midge populations reached to low equilibrium Levels within two or three years after the peak. 3. The survivorship curves of the pine needle gall midge showed a stop-like curves representing low mortality in its larval stage within galls at the both sites increasing in population density and stabilized in low level, but those at the sites that its density began to decrease following peak severity of damage showed much straightened survivorship curves having more constant mortality per unit time-intervals. 4. The survivorship differences relating to the state of infestation progress were evident for newly hatched larvae, larvae in galls and larvae or pupae in the soil. 5. The realized fecundity of female adults among tire potential eggs were ranging from 6.6% to 40.4% in accordance with the infestation progress and also the year surveyed. The major mortality in this stage was possibly influenced by the climatic conditions and the shortage of suitable pine needles for oviposition. 6. For the immature stages of newly hatched larvae in the tree crown, the survivorship trends showed obvious differences ranging from 15% to 85% in mortality between the sites with increasing and decreasing populations. The mortality factors in this stage were unfavorable morphological and physiological conditions of host needles ; they are narrowness and consequent flexibility of the needles and high rate of needle divergence in hatching season. 7. The mortality of larvae within galls were 3.4% at the minimum and 88.7% at the maximum, which reflected much heavier mortality at the sites just after peak severity of damage. Most of the mortality occured in this larval feeding period in galls was induced by the early withering of shoots or of galls themselves. 8. For sites with high population levels, intr.aspecific competition for food were recognized at the larva. stage in galls. 9. The total mortality for larvae and pupae in soi habitat was increased along with the stage of infestation progressed as 51.3% at site with. increasing population, 67.8 to 82.5 at site; with decreasing one and 80.7% to 88.7% at stabilized sites respectively. 10. The mortality of overwintering larvae in soi: until late March were higher at the site where follows peak severity as 34.2% to 55.8% in comparison with the figure of 30.9% and 24.8% to 39.0% at sites with increasing and stabilized population respectively. 11. The periodic mortality of larvae and pupae in soil since early April was 29.5% to 37.5% at increasing sites, 35.3% to 60.0% at decreasing sites and 67.3 to 85.3% at stabilized sites. These differences during this period were caused mainly by its parasites. 12. Female/male sex ratio of adults collected in emergence traps varied along with different sites and were correlated with population density. 13. Parasitization by Platygaster matsutama was high at decreasing and stabilized population sites, but that by Inostemma seoulis was negligible at all sites, and coincidental parasite species with host had high parasitism. The density increasing of parasite had delayed-density dependent process following the peak density of the host. 14. The parasites have probably weak functional response in host searching behavior and consequently their realized fecundity was very low. 15. The species composition and dive