Analysis involving autocorrelation functions indicated the presence of cyclic components in the changes in I. persulcatus population as well as in certain climatic parameters. Three orders of cycles are distinguished, their mean duration comprising 5.5; 11.1 and 22.2 years. High number peaks of I. persulcatus repeated with a mean period of 22 years in 1938-1942, 1959-1964 and 1983-1986, coinciding with the periods of solar energy decline in odd 11-year cycles. According to the established regularity, the next considerable rise in I. persulcatus number should be expected in 2003-2009 with a peak in 2004-2006.