Influence of feeding status and physiological condition on supercooling points of adult boll weevils (Coleoptera: Curculionidae)

Abstract

Cold bath studies were conducted to examine the impacts of midgut content and fat body condition on supercooling points of adult boll weevils, Anthonomus grandis Boheman. The presence of solid food in weevil midguts significantly raised the supercooling points of weevils. Supercooling points of recently fed weevils with solid food present in their midguts ranged from -6.2 to -16.0°C, with a mean ± SD of -10.9 ± 1.9°C, whereas supercooling points of unfed weevils with empty midguts ranged from -10.2 to -20.2°C, with a mean ± SD of -16.0 ± 2.1°C. The mean supercooling point of weevils whose midguts contained colored traces of food from previous feeding was between those of recently fed weevils containing solid food and those having empty midguts. These findings indicate that the influence of feeding on supercooling points of weevils is related to the quantity and/or condition of midgut contents in weevils. No relationship was detected between the supercooling capabilities of weevils and amounts of hypertrophied fat bodies present for either fed or unfed weevils. Additionally, there was no significant difference in mean supercooling points between male and female weevils, and no relationship was detected between the supercooling points of weevils and their age. These results show that presence of food residues in the boll weevil midgut can have a significant effect on supercooling points of weevils, and indicate that the recent feeding history and midgut condition of weevils should be documented or at least considered in future supercooling and overwintering survival studies.