Some Ecological Factors Affecting the Grasshopper Populations of Western Canada

Abstract

The underlying causes of grasshopper outbreaks in Western Canada are of interest both as an academic problem in insect population dynamics and as a practical problem in modern agriculture. Grasshopper populations reach their annual low point in early July when they are in the adult stage and increase sharply in the fall at the time of oviposition. Any factor that influences the grasshoppers during this period may have a marked effect on the outbreak of the following year. The relationship between grasshopper population numbers and proceeding fall temperatures may either control grasshopper populations directly by affecting their physiology or indirectly by affecting their parasites, predators, and diseases. Studies at the University of Saskatchewan aimed at solving this problem include investigation of the microclimate to which grasshoppers are subjected under field conditions, a survey of their feeding habits as shown by crop analyses, and a study of their oviposition behaviour. On the basis of available information an attempt is being made to predict future outbreaks at least 6 months in advance.