To elucidate the relationship betwe

To elucidate the relationship between diapause and cold hardiness in the oriental corn borer, Ostrinia furnacalis, the levels of
various substances, cold hardiness and respiration were measured in diapausing and post-diapausing overwintering larvae. Under
field conditions, diapause terminated between November and January, although O2 consumption, measured at 20°C in the laboratory,
remained at a high level from October to January. Glycerol content was low during October and November but greatly increased
during December and January. Serine was the most abundant of the free amino acids, and its concentrations were especially high
during October and November, while the concentration of alanine increased in December and January. Under laboratory conditions,
glycerol levels were low in diapausing larvae, and in post-diapausing larvae that were acclimated at either high temperatures or
under anaerobic conditions, while they were high in post-diapausing larvae kept under aerobic, low temperature conditions. The
survival rate (cold hardiness) was strongly correlated with glycerol content but not with serine or alanine levels. These results
suggest that O. furnacalis has a highly developed cold hardiness mechanism in which termination of diapause enables the larvae
to increase glycerol levels when the temperature decreases.  2000 Elsevier Science Ltd. All rights reserved.