Observations were carried out at Hoshioki in Hokkaido, Japan; 1974-1977. Male mating and feeding activities continue from 7:00 to 18:00, while opposition is restricted to 15:00-19:00. Influences of weather conditions are analyzed. Flight is inhibited by a temperature lower than 12°C. Pre-mating activity of males is suppressed by a temperature lower than 16°C. The reproductive period continues from early June to mid July, with a peak of activities in mid June. The mechanisms and adaptive values of these bionomic features are discussed.