Physiological Ecology of Insect Overwintering

We are especially interested in ecological interactions between environmental conditions and the regulation of seasonal cold-hardening and winter survival. Temperature, photoperiod, and the physiological condition of the host plant are important cues for the induction of glycerol, sorbitol and other cryoprotectant synthesis as well as factors influencing the supercooling point, the temperature at which an insect freezes (Lee and Costanzo 1998). Another long-standing interest of our lab is the nature of chilling and freezing injury and cryoprotection at cellular (i.e., fat body and Malpighian tubules) and organismal levels. Recently, we used fluorescence microscopy to demonstrate cold-hardening at the cellular level (Yi and Lee 2003). We also recently demonstrated that even when frozen, insects are able to undergo diapause development (Irwin et al. 2001).

Other work focuses on ecological and evolutionary aspects of cold tolerance and winter survival. In winter, insects must not only be able to survive cold but also desiccation. Recent studies in our lab have found that even soft-bodied larvae and prepupal stages have exceptional desiccation resistance that rivals or exceeds the most desiccation-tolerant insects (Ramlov and Lee 2000; Nelson and Lee in press). Mild winters may be more detrimental to insects than colder ones; relatively warm hibernacula reduce survival and fecundity by elevating the metabolic rate, which causes excessive depletion of energy stores, particularly in species that rely on reserves accumulated during the autumn to produce eggs the following spring (Irwin and Lee 2003; Williams et al. 2003).