The observation of activity and behavior of imagos is vital when conducting system analysis of Theclini. This paper discusses the authors' approach in investigating such activity by way of observing the flight activity of three types of Theclini in Japan—Chrysozephyrus brillantinus,Favonius taxila, and Favonius jezoensis—from 2001 to 2005 in two locations: Iiyama city and Oomachi city, Nagano Prefecture. Specifically, this paper describes their flight activity and relationship to the temperature and illuminance recorded at the time of observation.