Aspects of Overwintering in the Cabbage Armyworm, Mamestra brassicae (Lepidoptera, Noctuidae) : I. Supercooling Points and Contents of Glycogen and Trehalose in Pupae

Abstract

The supercooling point (by spontaneous freezing) of Mamestra brassicae LINNE is about -20.0°C in both diapausing and non-diapausing pupae. The supercooling ability is considerably reduced by contact with moisture. Pupae begin to freeze at -4°C in muddy water and at -4.9 to -7.8°C in soil of various water contents. Trehalose content in diapausing pupae increases with days after pupation, attaining a maximum within 30 days, with a concomitant decrease of glycogen. Further, trehalose content tends to decrease with incubation (at 22°C) of diapausing pupae kept at 4°C for 40 days. In non-diapausing pupae trehalose accumulates less but the content is slightly increased over that in prepupae. Non-diapausing pupae develop a supercooling ability at a level comparable to that in diapausing pupae despite poorer trehalose accumulation. The supercooling ability in this species is thus probalby determined independent of trehalose accumulation.