The Influence of the Prevailing Weather on the Numbers of Meromyza variegata Meigen (Diptera, Chloropidae) Caught with a Sweepnet

Abstract

The relative size of catches of the fly Meromyza variegata. obtained by sweeping grass during the summer of 1953, showed the microclimate of the grass to be directly related to prevailing conditions of air temperature, wind, rain, and solar radiation, as modified by the vegetation structure. Statistical analysis of the results showed that, apart from changes in population size, an increase of wind speed is clearly associated with a reduction in the number of flies caught. The occasionally discrepant sizes of the catch of both this fly and the closely related M. saltatrix could be explained by the dependence of the size of catch on weather conditions. Although each factor had not necessarily a significant influence on the catch size in itself, the multiple regression of the catch size on all the measured factors gave predicted catches in good agreement with the observed values. The probable mechanisms of the effect of each weather factor on catch size and an apparently greater reaction of the male flies to differing weather conditions are discussed.