Read/Search this Article
During the course of 1983, seasonal dynamics of the on-tree population of the adult Viburnum leaf beetle, Pyrrhalta humeralis (CHEN), were monitored and estimated using Jolly's capture-recapture method at Matsudo, Chiba-Pref.. Associated seasonal fluctuations of their feeding intensity on the Viburnum leaf were also observed under the quasi-natural conditions in a large outdoor cage. With these basic information, factors responsible for population dynamics of adult beetles were investigated. Results of the observation indicated that beetles emerged during the two months of June and July, having its peak in late June. The greatest mortality for adult beetles came within a couple of weeks after their emergence, and only those which could consume a considerable amount of food during this period seemed to advance to the subsequent summer diapause. During this less-active period, survival of adult beetles was fully assured with little mortality, although their emigration and immigration around the tree were observed to be common even at this stage. As a result, on-tree population of the beetles had a peak in late August after the diapause termination at the observation site.