Population structure and seasonal activity of Ommatissus lybicus in Bam Region of Iran (Homoptera: Tropiduchidae)Abstract : The spatial distribution and population flactuation of two generations Ommatissus lybicus de Bergevin (Hom.: Tropiduchidae) were determined in the Bam region, Iran, in 2008. Spatial distribution pattern of O. lybicus was described at two generations using variance to mean ratios, Taylor?s power law coefficients and Iwao?s patchiness regression methods. The spatial distribution pattern of this pest was aggregated. At first generation, the collected data had better fit to Taylor?s model for nymphs, adults and both of them (r2=0.980, 0.839 and 0.968, respectively) in comparison with Iwao?s model (r2= 0.935, 0.836 and 0.787, respectively). Taylor?s model explained the distribution data at second generation for nymphs, adults and both of them (r2= 0.971, 0.966 and 0.843, respectively) better than Iwao?s model (r2= 0.910, 0.905 and 0.833, respectively). The nymphs were active from April to May and August to October, at first and second generations respectively. Adults of the first and second generations were active from May to June and September to November, respectively. By increasing temperature, O. lybicus had aestivation in the egg stage for 5 weeks. Spatial distribution coefficients can be used to develop a sampling program and to estimate the population dynamics of this pest accurately.