Invasive hornet Vespa velutina nigrithorax, which was found at Yeongdo, Busan for the first time in 2003, has been spreading to whole area of Gyeongnam and even to some southern parts of Gyeongbuk for last ten years, causing lots of damage. Urban area of Busan already showed dominant distribution of V. v. nigrithorax marking more than 90% of emergence rate by its spread, while in forest area, its rate had not been so high due to its competition with native Vespa species. However, recently dominance of this species was detected continuously in some forests in Busan.
Thus, this study conducted a survey of emergence rate of V. v. nigrithorax at Mt. Bongraesan, Yeongdo-gu, Busan where it was discovered for the first time and also conducted observation of its behaviors related with competition for prey in order to understand its ecological niche relation with native Vespa species. Consequently, 4,560 individuals were collected in total out of main five species of Vespa at Mt. Bongraesan. Of these, V. mandarinia made up 8.7% with 397, V. crabro flavofasciata 21.2% with 965, V. analis parallela 23% with 1,048, V. simillima simillima 0.6% with 27, while V. v. nigrithorax made up 46.6% with 2,123, demonstrating the aspect of the most dominant emergence of V. v. nigrithorax. On the other hand, ecological niche due to competition for prey between V. v. nigrithorax and native Vespa species was revealed in the order of V. mandarinia >> V. crabro flavofasciata > V. analis parallela ≥ V. v. nigrithorax, telling ecological niche of V. v. nigrithorax was relatively low compared to native Vespa species, despite its dominant emergence. This background may explain why in forest area, V. v. nigrithorax had a limited spread and dominance compared to urban area of less competition among Vespa species. On the other hand, V. v. nigrithorax seems to have advantage in catching small insects due to developed agility with its smaller size than other Vespa species, and its rapid spread and adaptation in the local environment may be mainly attributable to its far more number of individuals than native Vespa species and consequent high reproductive rates and diversity of nesting site.

• Moon-Bo Choi(Department of Life Sciences, Yeungnam University)
• Jeong-Kyu Kim(Department of Biological Sciences, Hanseo University)
• Jong-Wook Lee(Department of Life Sciences, Yeungnam University)