Population Fluctuations of the European Corn Borer, Pyrausta Nubilalis, at Waseca, Minnesota, 1948 to 19571

Publisher Website
Google Scholar
Abstract
The abundance of the various stages in the borer population fluctuated in a random manner. Young larvae always suffered high mortality and few of them reached maturity, even under the most favorable conditions. Of the biological events recorded, percent of summer pupation showed the greatest variability, hence might be a more important determinant of the direction and magnitude of borer-population fluctuations than the larval mortality. The quantitative relationships of the summer and fall populations in a given year are affected by the size of the first-generation population, the amount of summer pupation, and the favorability of the environment for development and survival of the second generation. A summer mature larval population of any given size might give rise to a fall population many times larger, or to one only a fraction of the original size. Fluctuations of the populations of different life stages followed different patterns, so that the mean interval between two successive peaks of abundance was not the same for all stages. Fluctuation of all stages within years and between years was so haphazard as to suggest an independence of each other and a dependence upon the equally haphazard vagaries of the weather. The population dynamics of the species in southern Minnesota suggest that here it is occupying a fringe area in its distribution, where the relatively harsh climate produces random fluctuation at a relatively low level of abundance. Competetive mechanisms seem not to have been important in determining either the population levels or their fluctuations.

This publication has 0 references indexed in Scilit: