Influence of Temperature on Adult Biology and Population Growth of Bracon kirkpatricki1, 2, 3

Abstract

The influence of temperature on adults of Bracon kirkpatricki (Wilkinson), a braconid parasite of the pink bollworm, was studied to quantify potential population growth responses. Studies were made at constant temperatures of 20, 25, 30, 32.5, and 35°C, and under truncated day-night temperature models of 33-14, 36-20, and 36-28°C. Data were collected on daily fecundity and survival of individual adult females for each regime, and additional data were collected on developmental time, survival, and sex ratio of the immature stages for the day-night regimes. The combined data on the immature and adult stages were used to construct life tables for the calculation of several population growth statistics: the intrinsic rate of natural increase (rm), net reproductive rate (Ro), mean generation time (T), finite rate of natural increase (λ), and stable age distribution. Rising temperatures generally caused the rate of population growth (rm) to rise. Increased value of rm resulted mainly from the influence of rising temperature in shortening developmental periods and increasing daily fecundity during the initial period of adult longevity. The largest increases in rm occurred between 20 and 25 °C in the constant temperature regimes and between nocturnal temperatures of 20 and 28°C in the day-night regimes. Above 25°C, rm continued to rise to a peak value at 32.5°C followed by a slight decline at 35°C.