Temperature-dependent development and fecundity models for Bracon mellitor Say, primary parasite of the boll weevil

Abstract

Maximum Bracon mellitor Say survival occurred at 26.7°C but was not significantly different between 21.1 and 32.2°C. Fertility did not significantly differ between 21.1 and 37.8°C. However, larval mortality significantly decreased above 32.2°C. Upper and lower developmental thresholds occurred at approximately 40.56 and 12.78°C, respectively. Developmental times consistently decreased with increasing temperatures from a mean of 43.3 days at 15.6°C to 9.3 days at 37.8°C for females. At the same temperature, developmental times were 46.4 and 9.3 days for males. The percent of total developmental time spent in each stage was 7.13, 25.04, 16.38 and 51.51 for eggs, larvae, pre-pupae and pupae, respectively. A general poikilotherm developmental model was used to describe B. mellitor development and was based on the gas constant and 6 thermodynamic constants unique to B. mellitor. Emergence patterns predicted by the developmental model were compared with observed B. mellitor adult emergence. Reasons for some departure from model predictions were discussed. In general, the poikilotherm developmental model reasonably described B. mellitor development under both constant and variable temperatures and offered explanations for observations at extreme temperatures. Results of field studies were compared to model predictions and, in general, these agree with the model. ...