Development of the European Corn Borer at Controlled Constant and Variable Temperatures1

Abstract

The European corn borer, Ostrinia nubilalis (Hübner), reacts to constant and variable temperatures in approximately the same manner as have many other insects studied in the past. The eggs, larvae, and pupae were treated as separate entities and were found to react differently when subjected to certain temperatures and combinations of temperatures. When the durations of each stage reared at controlled constant temperatures are plotted against temperature, a curve taking the shape of a hyperbola is formed. When the reciprocals of these durations are plotted against temperature, a straight line, the velocity line, is formed. The velocity line departs at its upper and lower limits in all cases. The straight segment of the line is the normal of temperature; this range varies between the immature stages of the corn borer. The normal range of development is within the temperatures 65°–80°F for eggs, 60°–90°F for larvae, and 60°–85°F for pupae. Controlled variable temperatures have little effect on the durations of the immature stages of the corn borer when the temperatures are within the normal range of development. More acceleration of the rate of development was present in the experiments with the lower weighted mean temperatures. The egg stage is the only immature stage showing no acceleration when subjected to variable temperatures. There is evidence that certain variable temperatures will retaid the rate of development of the egg stage. The thresholds of development are different for the immature stages of the corn borer. The threshold of development is about 57.3° for the egg stage, about 52°F for the larval stage, and approximately 54.5°F for the pupal stage. Because the velocity line departs from its straight line course at its lower limit, the thresholds of development mentioned above are theoretical; the actual thresholds of development are below these temperatures.