MODELING THE RELATIONSHIP BETWEEN COLD INJURY AND ACCUMULATED DEGREE-DAYS IN TERRESTRIAL ARTHROPODS

Survival at various low temperatures and various exposure durations wa s quantified using regression models which calculate two parameters: U LCIZ and SIT. The temperature that cause no significant mortality duri ng prolonged exposure was called upper limit of cold injury zone (ULCI Z). The difference between ULCIZ and the exposure temperature was defi ned as temperature effective in cold injury. The product of exposure d uration and temperature effective in cold injury represents the acquir ed (accumulated) dose of a stressor, i.e. chilling, and is called sum of injurious temperatures (SIT), expressed in degree-days (DD or Kd). We calculated the parameters for six hexapod species. The ULCIZs range d from -17 degrees C (diapausing overwintering moth pupae) to +11 degr ees C (tropical cockroach), the SITs from 14 to 300 Kd. Estimation of the parameters allows to predict survival under variety of conditions and to compare level of cold hardiness among samples.