Seasonal Variation in the Respiration of Migrant Boll Weevils (Coleoptera: Curculionidae) and the Effects of Food and Environmental Conditions on Those Captured in August-September1

Abstract

Boll weevils, Anthonomus grandis grandis Boheman, captured in pheromone traps (8 km from cotton) in August-September were different from those found in cotton fields as reported in other studies and had the characteristics of migrants. Boll weevils captured in October were different from those captured in August–September. Those captured in August-September had a high level of respiration: only 5% used <1 μl oxygen per mg boll weevil per h; after 13 October, ca. 60% used <1 μl oxygen. After 2 weeks of feeding on squares and bolls, boll weevils captured in August–September had the same mean respiratory rate regardless of food, photoperiod, or temperature. Some boll weevils that were fed bolls had respiration rates <1 μl oxygen per mg boll weevil per h; only one group of weevils fed squares had this low rate. Boll weevils that were fed squares for 2 weeks at 21°C with either a photoperiod of 13:11 or 11:13 (L:D), and then survived for 1 month at 13°C and a photoperiod of 11:13, had a significantly higher rate of respiration than boll weevils fed squares at 27°C. In contrast, boll weevils that survived 1 month at 13°C with a photoperiod of 11:13, after being fed bolls for 2 weeks at 21°C with a photoperiod of 13:11, had a significantly lower rate of respiration than those fed bolls at 27°C. All survivors that had fed on bolls had a higher rate of respiration than those fed squares. Newly emerged boll weevils that were fed squares, but not exposed to 13°C, showed an increased rate of respiration. Individual determination of the respiration level may provide a nondestructive method to separate reproductive from potentially diapausing boll weevils.