Physical Factors Affecting the Fall Migration of the Egyptian Alfalfa Weevil, Hypera brunneipennis (Coleoptera: Curculionidae): A Regression Analysis 1

Abstract

In an attempt to determine the primary physical factors affecting the fall migration of the Egyptian alfalfa weevil, a multiple regression analysis, based on a 2-year study in north-central California, was conducted. Physical factors monitored on a daily basis were temperature, wind, cloud cover, evaporation, and precipitation. Four aspects of daily temperature were considered: maximum, minimum, difference between maximum and minimum, and average. Total wind movement and direction was studied. The average number of adult weevils recorded per square yard of trap per sample day was used as the dependent variable and the above-mentioned physical factors as the independent (predictor) variables. We analyzed the data for both study years and obtained a total reduction of 77.6% in the residual variance the first year and 71.3% for the 2nd. Daily temperature difference was by far the single most important factor in reducing the residual variance and, hence, appears to be the most important factor influencing the fall weevil migration.