Effects of temporary cooling on larvae of Idaea inquinata (Scopoli) (Lepidoptera Geometridae)

Idaea inquinata develops on dried plants with a preference for medicinal plants. The survival of second and fourth instars larvae of I. inquinata exposed to 6 and -18±1 °C, for different periods of time, was observed. Groups of 20 larvae were placed at 6±1 °C 60±5% R.H. for periods of 15, 18, 20 and 25 days and then put in thermostatic chamber at 26±1 °C, 70±5% R.H. Tests were controlled after 1, 2, 3, 8, 15 and 23 days until adults emergence. The same procedure was used for tests at -18 °C with exposure times of 4, 8 and 24 hours. For all the tested periods at 6±1 °C, a mortality higher than 95% was observed in second instar larvae after 1 day at 26 °C. A 100% mortality was observed on the second day at 26°C after treatment at 6 °C for 18, 20, 25, on the third day for 15 days treatment. Few fourth instar larvae, placed for 25 days at 6 °C, were alive after 8 days at 26 °C, but they didn’t emerge as adult; when exposed for 15, 18 and 20 days few individuals developed to adult. Larvae of I. inquinata were susceptible to the treatment at -18 °C. A 100% mortality was observed after 24 hours, when second and fourth instar larvae were treated for 4 hours at -18 °C.