FACTORS AFFECTING LOW-TEMPERATURE SURVIVAL OF CINARA-PILICORNIS EGGS ON SITKA SPRUCE

Oviparous C. pilicornis deposited eggs in October and early November, the dry weight, but not the fresh weight, decreasing during winter. Diapause terminated in early March, eggs hatched in early May. Mean egg supercooling points varied during the winter, the variation being related to the temperature in the period preceding sample collection. Both glycerol and mannitol were isolated from the eggs. Mannitol levels decreased to zero by mid-winter, levels increasing after diapause termination. Glycerol levels increased up to diapause termination and thereafter decreased, none being present just prior to egg hatch. Neither glycerol nor mannitol were related to supercoolingability, the variation being related to low temperatures which possibly induced changes in the levels of an unknown factor. © 1979 Swets & Zeitlinger B.V.