Abstract
The redback spider (RBS) was discovered at a reclaimed island site in Nishinomiya City, Hyogo Prefecture in October 2000. Nishinomiya City consequently initiated field surveys and control programmes in October of the same year. The overall results of the control measures up to October 2005 were summarized according to the survey period, month, address in town/street, number of collected male/female/egg sac specimens, and number of inspectors. Some of the data were then plotted onto a map using GIS and remote sensing by aerial photographs in order to analyze the distribution, dispersal fluctuations and causal factors thereof, the effectiveness of control programmes and the possibility of eradication. The number of collected specimens peaked in 2002 and then declined, but the distribution of the spiders has expanded rapidly since 2003. In addition, significant areal differences in the density and habitation frequency have occurred. Furthermore, analysis of aerial photographs and development related documentation reveal a clear relationship between the invasion and establishment of RBS and the subsequent urgent housing development after the Great Hanshin-Awaji Earthquake (January, 1995). The results clearly show that the survey season, continuous monitoring and control activity of RBS are extremely important to reduce the population density of RBS in the accidentally infested areas.
