Seasonal changes in glycerol content and supercooling points of Megachile rotundata (F.) and M. relativa Cress.

Abstract

Supercooling points of prepupae of the exotic species Megachile rotundata during storage at 5 °C are not closely related to glycerol content and are not sufficiently low to avoid freezing outdoors in southern Alberta. In contrast, supercooling points of prepupae of the indigenous species M. relativa are inversely related to glycerol concentrations, which are double those of M. rotundata and are low enough for successful overwintering. Neither species is frost-tolerant.Older feeding larvae of M. rotundata also synthesize glycerol in the fall, probably in response to cold night temperatures.