Seasonal changes of glycogen/trehalose contents,supercooling points and survival rate in mature larvae of the overwintering soybean pod borer Leguminivora glycinivorella

The mature larvae of the soybean pod borer Leguminivora glycinivorella, spend over 9 months (October-next August) in the inactive state until pupation down to 3 cm below the surface in soil. Trehalose content of inactive larvae increases in early winter, attaining a maximum (ca 30 mg/g), and decreases in spring, with a concomitant decrease and increase of glycogen. The median supercooling points seasonally change from ?19.8°C (October) to ?25.0°C (February), and to ?17.0°C (June). The lower supercooling points in winter are in part due to the absence of unusually high values (> ?18°C). The increase in trehalose does not seem to be effective in depressing the supercooling points. The larvae are freeze-intolerant, but ambient temperatures in outdoor conditions are always above the supercooling points. The survival rates are very high throughout the inactive period.