The effects of temperature on population processes of the southern pine beetle, Dendroctonus frontalis Zimmermann

Abstract

Temperature influences development and mortality of the southern pine beetle, Dendroctonus frontalis Zimmermann. Because the insect is difficult to observe and rear, the effects of temperature on development and mortality have not been measured. Studies were done to measure these effects. The overall goal was to provide data for a simulation model of D. frontalis population dynamics. There were 6 specific objectives: to measure rates of development and mortality of eggs; to measure rates of development and mortality of larvae, pupae, and callow adults; to measure rates and proportions of reemergence of parent adults; to measure the longevity of brood adults; to describe mathematically the effects of temperature on the various stages and to use the models to predict field events; and to integrate the results into a better understanding of how temperature impinges on D. frontalis. Data were gathered in constant temperature experiments on eggs, larvae, pupae, callow adults, reemergence of parent adults, and longevity of brood adults. Eggs served as the benchmark for the relationships between development time, mortality, and constant temperature. A plot of egg development time (ordinate) versus constant temperature (abscissa) formed a backwards J-shaped curve. Eggs hatched between 10° and 33.6°. Eggs held at identical conditions did not hatch all at once. Rather, there was a frequency distribution of egg development times. The contours of the frequency distributions changed with temperature. Egg mortality was 100% outside the 10°-33.6° range. Within that range about 15% of the eggs died. Due to difficulties in rearing larvae, data on this stage were incomplete. Larvae developed at temperatures between 12.5° and 31.1°, but the form of their temperature-development curve could not be defined. The contours of larval development distributions changed with temperature. Larval mortality was 100% outside the 12.5°-31.1° range. Within that range mortality varied widely, averaging 26%...