Abstract:   In order to explore the effect of temperature on migratory insect behavior, such as stratification, temperature selection of flying Helicoverpa armigera moths was studied using a continuous temperature gradient device in the laboratory. The results showed that all the tested individuals exhibited significant choice behavior for temperatures. Measured in groups, the tested moths actively selected the temperature range from 20 to 22℃, which was evaluated as the optimal flight temperatures of the moth. In this temperature range, moths had the maximum frequency and the longest time of wing beat. The flight durations of the tested moths were compared in different temperature intervals, and the results showed that the moths made more obvious choices in the gradient from 16 to 22℃ than in the gradient from 19 to 30℃, suggesting that the temperature in the cold season has more significant effect on stratification of the moth than in the warm season. The wing beat frequency was affected significantly by the continuous flight time, suggesting that there exists a relationship between flight height and energy expenditure of insect during migration.

Key words: Helicoverpa armigera, migration, temperature gradient, optimal flight temperature, active choice, stratification