Cold hardiness in Spodoptera exigua (Lepidoptera: Noctuidae)

The beet armyworm, Spodoptera exigua (Hubner), migrates long distances to find suitable conditions, but the possibility of its overwintering in specific hibernacula in temperate regions has been suspected. Supercooling points differed among developmental stages. Field collected larvae had higher supercooling points than laboratory-reared larvae. No beet army-worms survived below their supercooling points. Most developmental stages showed a rapid cold hardiness in response to sublethal temperature to increase their survival capacities at lethal temperatures. This rapid cold hardening was correlated with the increase of hemolymph osmolalities, polyol(s) production, and cold-induced proteins. Although sublethal temperature increased the ability to survive subzero temperatures, its prolonged exposure was lethal to the beet armyworm.