COLD HARDINESS IN THE JAPANESE BEETLE, POPILLIA JAPONICA NEWMAN

¹ NATIONAL RESEARCH FELLOW IN THE BIOLOGICAL SCIENCES

1. Cold hardiness, both to the intensity factor and to the quantity factor of low temperature, were studied in the second and third instars of the Japanese beetle. Brief observations were made on pupæ and adults with regard to cold hardiness.

2. Japanese beetle larvæ are somewhat periodic in their cold hardiness to the intensity factor of low temperature, less so than the oak borers previously studied and more so than the aquatic insects.

3. Disease incidence, nutritional state, and degree Of dehydration are associated with cold hardiness to the intensity factor of low temperature.

4. Development of cold hardiness to the quantity factor of low temperature is associated with loss of cold hardiness to the intensity factor except in extremely dehydrated individuals.

5. Marked permeability changes associated with enzyme action occur at the vital temperature minimum.