Lethal Limits of Low Temperature for the Alfalfa Weevil in Illinois

Abstract

The supercooling points of eggs, larvae, pupae, and adults of the eastern strain of Hypera postica (Gyllenhal) were determined in a laboratory study. Measurements based on the supercooling point showed that the egg stage was more cold-hardy than the other stages, and the newly hatched larvae were more cold-hardy than more mature larvae. Adults reared at 72°F showed a definite lowering in the supercooling point with increase in age. Over the same time period adults stored at 30°F showed only a slight lowering in the supercooling point with increase in age. Some observations were made also with adults of the western strain. There was no significant difference in cold-hardiness between adults of the eastern and western strains.