[Supercooling capacity and cold hardiness of the Pararcyplera microptera meridionalis (Orthoptera: Acrididae) eggs].

Using the thermocouple method, the supercooling point (SCP) and cold hardiness of Pararcyplera microptera meridionalis eggs were measured in the laboratory. The soil water content significantly affected the water content of pre-diapause eggs, but had no significant effect on the SCP, and the water content of pre-diapause eggs rose with the increasing soil water content. There were highly significant differences among the SCPs, water contents or fat contents in the eggs at different developmental stages. With the egg' s development, the water content decreased from 51.5% at oviposition to 46.8% in 120 days after oviposition, the fat content increased from 10.5% (fresh mass)/19.0% (dry mass) to 14.5% (fresh mass)/28.9% (dry mass), and the SCP declined from -23.5 degrees C to -30.0 degrees C. There was a significant correlation between the SCP and the water content or fat content. The SCPs of deep-diapause eggs were lower than those of pre- and early-diapause eggs. The different low temperatures and treatment durations significantly affected the survival rate of diapause eggs. The lethal low temperature (Ltemp50) for 12 h exposure was -27.3 degrees C and the lethal time (Ltime50) at -25 degrees C was 22.73 days. As the mean SCPs of diapause eggs was much similar to their Ltemp50, the SCP could be considered as a good indicator of cold hardiness for P. m. meridionalis eggs and this species is a freeze-intolerant insect.