Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/1997
Publication Date: N/A
Interpretive Summary: The effects of temperature on reproductive development of the boll weevil were examined at constant temperatures ranging from 12.8 degrees C (55 degrees F) to 35.0 degrees C (95 degrees F) under a day-length of 13 hours of light. Reproductive development was monitored by dissecting weevils at different ages. Mathematical equations (logistic functions) were used to describe at what ages 50% and 90% of females would contain eggs, eggs with visible yolk, mature eggs, and 50% and 90% of males would contain early reproductive testes, late reproductive testes, and seminal vesicles (which store sperm) filled with sperm. These development times in days were fitted to development rate curves to estimate development rates. Results showed that temperature dramatically influenced reproductive development. Development occurred faster as temperature increased except at the highest temperature. Both the lowest and highest temperatures particularly slowed development compared to the next closest temperatures. The lower temperatures did not cause weevils to show signs of diapause, a form of dormancy used to survive the winter season. This study suggests that earlier studies of diapause in which the effects of temperature on reproductive development rate were not considered, should be reexamined. Such reexamination may supply information useful in improving control measures directed at diapausing populations of weevils.
Technical Abstract: Temperature dependence of boll weevil, Anthonomus grandis Boheman, reproductive development was examined at constant temperatures of 12.8, 18.3, 23.9, 29.4, 32.2, and 35.0 degrees C and a 13:11 (L:D) h photoperiod by performing dissections at specific ages. Logistic functions were used to describe age-frequencies of the presence of eggs, eggs with visible yolk, mature eggs, early reproductive testes (beginning of visible sperm accumulation in the centers of testis lobes), late reproductive testes (visible sperm accumulation in outer areas of testicular follicles), and filled seminal vesicles. Development times for 50% and 90% of the populations to attain these development stages were estimated from the logistic functions and biophysical developmental rate models were fitted to the corresponding development rates. Results indicated a marked temperature dependence of reproductive development, with both low- and high-temperature inhibition at observed temperature extremes. Exposure to lower temperatures did not induce morphological characteristics of diapause. These results suggest a need to reexamine previous studies of diapause induction in which differences in physiological ages of weevils among induction regimes were not considered.