SURVIVAL OF COLORADO POTATO BEETLE (COLEOPTERA, CHRYSOMELIDAE) AFTER EXPOSURE TO SUBZERO THERMAL SHOCKS DURING DIAPAUSE

Adult Colorado potato beetles, Leptinotarsa decemlineata (Say), collected from the field in fall, were exposed to a 79-d period of controlled environmental conditions to simulate the diapause period. Following attainment of a constant temperature period (1-degrees-C), groups of beetles were subjected to cold shocks of -4, -6, -8, -10, and - 12-degrees-C lasting 4,6, 8, 10, and 12 h, respectively. Water was added to create differential soil moistures before cold shock was applied. Beetle survival was determined immediately following cold shock and at the conclusion of the simulated diapause. A dramatic reduction in survival occurred following cold shocks of < - 4-degrees-C, when survival was measured at the end of diapause. Mortality at -6 and -8-degrees-C was not expressed immediately after the cold shock. A small difference in soil moisture did not affect survival.