Longevity of Noctuid Moths in Relation to Certain Day-Time Weather Factors

Experiments on the longevity of noctuid moths in captivity were performed in connection with light trapping in 1968 and 1969. Longevity was found to be temperature dependent. In spring, moths lived for an average of 11.8 days, in summer for 4.2 days. Low temperatures in spring did not kill the moths; but prevented activity. During dry periods with high temperatures in the summer, death rate was very high, with significant positive correlations being found between the day mean and maximum temperatures and the death rate, and also between the day mean water vapour pressure deficit (WVPD) and the death rate. Strong winds during the day enhanced the negative effect of high day temperatures and high day WVPD. The actual effect on the moths is probably that of desiccation caused by rapid transpiration. In some multiple regression analyses on light trap catches significant negative regressions were found on the day mean and maximum temperatures, and on the day mean WVPD during months with high temperatures and low precipitation. At such times a significant positive regression was found on rainfall. High day temperatures alone, however, did not significantly affect the catch. Changes in light trap catches of noctuids are influenced by weather factors affecting the flight activity as well as by fluctuations in the number of moths in the area, fluctuations at least partly caused by day-time weather factors.