A Ten-Year Study of the Climatology of Melanoplus Mexicanus Mexicanus (Sauss.) (Orthoptera: Acrididae) in Saskatchewan1

High correlation coefficients between population indexes of adults of Melanoplus mexicanus mexicanus (Sauss) in various areas of Saskatchewan in the years 1943 to 1952 and records of weather factors in the same areas up to 14 months earlier suggest causal relationships The most critical months were June, August, and September of the previous year and June of the current year, the periods of hatching, nymphal development, oviposition, and hatching July was the least important of the summer months Temperature, especially daily minima, influenced later populations more than any other weather factor, during the previous June and August, and daily maxima during the previous August and the current June Sunshine was important during August and especially September. Correlation with rainfall during the previous August and September was high and negative. Evaporation showed erratic correlation.